[18] For the liquation it was necessary to maintain a reducing

atmosphere, otherwise the lead would oxidize; this was secured by

keeping the cakes well covered with charcoal and by preventing the

entrance of air as much as possible. Moreover, it was necessary to

preserve a fairly even temperature. The proportions of copper and lead

in the three liquation products vary considerably, depending upon the

method of conducting the process and the original proportions. From the

authors consulted (see note p. 492) an average would be about as

follows:--The residual copper--exhausted liquation cakes--ran from 25 to

33% lead; the liquated lead from 2 to 3% copper; and the liquation

thorns, which were largely oxidized, contained about 15% copper oxides,

80% lead oxides, together with impurities, such as antimony, arsenic,

etc. The proportions of the various products would obviously depend upon

the care in conducting the operation; too high temperature and the

admission of air would increase the copper melted and oxidize more lead,

and thus increase the liquation thorns. There are insufficient data in

Agricola to adduce conclusions as to the actual ratios produced. The

results given for the 6th charge (note 17, p. 512) would indicate about

30% lead in the residual copper, and would indicate that the original

charge was divided into about 24% of residual copper, 18% of liquation

thorns, and 57% of liquated lead. This, however, was an unusually large

proportion of liquation thorns, some of the authors giving instances of

as low as 5%.

[19] The first instance given, of 44 _centumpondia_ (3,109 lbs.) lead

and one _centumpondium_ (70.6 lbs.) copper, would indicate that the

liquated lead contained 2.2% copper. The second, of 46 _centumpondia_

(3,250 lbs.) lead and 1-1/2 _centumpondia_ copper (106 lbs.), would

indicate 3% copper; and in the third, 120 _centumpondia_ (8,478 lbs.)

lead and six copper (424 lbs.) would show 4.76% copper. This charge of

120 _centumpondia_ in the cupellation furnace would normally make more

than 110 _centumpondia_ of litharge and 30 of hearth-lead, _i.e._,

saturated furnace bottoms. The copper would be largely found in the

silver-lead "which does not melt," at the margin of the crucible. These

skimmings are afterward referred to as "thorns." It is difficult to

understand what is meant by the expression that the silver which is in

the copper is mixed with the remaining (_reliquo_) silver. The coppery

skimmings from the cupellation furnace are referred to again in Note 28,

p. 539.

[20] A further amount of lead could be obtained in the first liquation,

but a higher temperature is necessary, which was more economical to

secure in the "drying" furnace. Therefore, the "drying" was really an

extension of liquation; but as air was admitted the lead and copper

melted out were oxidized. The products were the final residual copper,

called by Agricola the "dried" copper, together with lead and copper

oxides, called by him the "slags," and the scale of copper and lead

oxides termed by him the "ash-coloured copper." The German metallurgists

distinguished two kinds of slag: the first and principal one, the

_darrost_, and the second the _darrsoehle_, this latter differing only in

that it contained more impurities from the floor of the furnace, and

remained behind until the furnace cooled. Agricola possibly refers to

these as "more liquation thorns," because in describing the treatment of

the bye-products he refers to thorns from the process, whereas in the

description of "drying" he usually refers to "slags." A number of

analyses of these products, given by Karsten, show the "dried" copper to

contain from 82.7 to 90.6% copper, and from 9.4 to 17.3% lead; the

"slag" to contain 76.5 to 85.1% lead oxide, and from 4.1 to 7.8% cuprous

oxide, with 9 to 13% silica from the furnace bottoms, together with some

other impurities; the "ash-coloured copper" to contain about 60% cuprous

oxide and 30% lead oxide, with some metallic copper and minor

impurities. An average of proportions given by various authors shows,

roughly, that out of 100 _centners_ of "exhausted" liquation cakes,

containing about 70% copper and 30% lead, there were about 63 _centners_

of "dried" copper, 38 _centners_ of "slag," and 6-1/2 _centners_ of

"ash-coloured copper." According to Karsten, the process fell into

stages; first, at low temperature some metallic lead appeared; second,

during an increasing temperature for over 14 to 15 hours the slags ran

out; third, there was a period of four hours of lower temperature to

allow time for the lead to diffuse from the interior of the cakes; and

fourth, during a period of eight hours the temperature was again

increased. In fact, the latter portion of the process ended with the

economic limit between leaving some lead in the copper and driving too

much copper into the "slags." Agricola gives the silver contents of the

"dried" copper as 3 _drachmae_ to 1 _centumpondium_, or equal to about 9

ozs. per ton; and assuming that the copper finally recovered from the

bye-products ran no higher, then the first four charges (see note on p.

506) would show a reduction in the silver values of from 95 to 97%; the

7th and 8th charges (note on p. 512) of about 90%.

[21] If Roman weights, this would equal from 6,360 lbs. to 7,066 lbs.

[22] One half _uncia_, or three _drachmae_ of silver would equal either

12 ozs. or 9 ozs. per ton. If we assume the values given for residual

copper in the first four charges (note p. 506) of 34 ozs., this would

mean an extraction of, roughly, 65% of the silver from the exhausted

liquation cakes.

[23] See note 29, p. 540.

[24]

Assuming Roman weights: 2 _centumpondia_ = 141.3 lbs.

2-1/2 " = 176.6 "

3 " = 211.9 "

3-1/2 " = 248.2 "

6 " = 423.9 "

[25] This description of refining copper in an open hearth by oxidation

with a blast and "poling"--the _gaarmachen_ of the Germans--is so

accurate, and the process is so little changed in some parts of Saxony,

that it might have been written in the 20th century instead of the 16th.

The best account of the old practice in Saxony after Agricola is to be

found in Schlueter's _Huette Werken_ (Braunschweig, 1738, Chap. CXVIII.).

The process has largely been displaced by electrolytic methods, but is

still in use in most refineries as a step in electrolytic work. It may

be unnecessary to repeat that the process is one of subjecting the

molten mass of impure metal to a strong and continuous blast, and as a

result, not only are the impurities to a considerable extent directly

oxidized and taken off as a slag, but also a considerable amount of

copper is turned into cuprous oxide. This cuprous oxide mostly melts and

diffuses through the metallic copper, and readily parting with its

oxygen to the impurities further facilitates their complete oxidation.

The blast is continued until the impurities are practically eliminated,

and at this stage the molten metal contains a great deal of dissolved

cuprous oxide, which must be reduced. This is done by introducing a

billet of green wood ("poling"), the dry distillation of which generates

large quantities of gases, which reduce the oxide. The state of the

metal is even to-day in some localities tested by dipping into it the

point of an iron rod; if it be at the proper state the adhering copper

has a net-like appearance, should be easily loosened from the rod by

dipping in water, is of a reddish-copper colour and should be quite

pliable; if the metal is not yet refined, the sample is thick, smooth,

and detachable with difficulty; if over-refined, it is thick and

brittle. By allowing water to run on to the surface of the molten metal,

thin cakes are successively formed and taken off. These cakes were the

article known to commerce over several centuries as "rosetta copper."

The first few cakes are discarded as containing impurities or slag, and

if the metal be of good quality the cakes are thin and of a red colour.

Their colour and thinness, therefore, become a criterion of purity. The

cover of charcoal or charcoal dust maintained upon the surface of the

metal tended to retard oxidation, but prevented volatilization and

helped to secure the impurities as a slag instead. Karsten (_Archiv._,

1st series, p. 46) gives several analyses of the slag from refining

"dried" copper, showing it to contain from 51.7 to 67.4% lead oxide, 6.2

to 19.2% cuprous oxide, and 21.4 to 23.9 silica (from the furnace

bottoms), with minor quantities of iron, antimony, etc. The "bubbles"

referred to by Agricola were apparently the shower of copper globules

which takes place upon the evolution of sulphur dioxide, due to the

reaction of the cuprous oxide upon any remaining sulphide of copper when

the mass begins to cool.

HISTORICAL NOTE.--It is impossible to say how the Ancients refined

copper, beyond the fact that they often re-smelted it. Such notes as we

can find are set out in the note on copper smelting (note 42, p. 402).

The first authentic reference to poling is in Theophilus (1150 to 1200

A.D., Hendrie's translation, p. 313), which shows a very good

understanding of this method of refining copper:--"Of the Purification

of Copper. Take an iron dish of the size you wish, and line it inside

and out with clay strongly beaten and mixed, and it is carefully dried.

Then place it before a forge upon the coals, so that when the bellows

act upon it the wind may issue partly within and partly above it, and

not below it. And very small coals being placed round it, place the

copper in it equally, and add over it a heap of coals. When by blowing a

long time this has become melted, uncover it and cast immediately fine

ashes of coals over it, and stir it with a thin and dry piece of wood as

if mixing it, and you will directly see the burnt lead adhere to these

ashes like a glue, which being cast out again superpose coals, and

blowing for a long time, as at first, again uncover it, and then do as

you did before. You do this until at length by cooking it you can

withdraw the lead entirely. Then pour it over the mould which you have

prepared for this, and you will thus prove if it be pure. Hold it with

the pincers, glowing as it is, before it has become cold, and strike it

with a large hammer strongly over the anvil, and if it be broken or

split you must liquefy it anew as before. If, however, it should remain

sound, you will cool it in water, and you cook other (copper) in the

same manner." Biringuccio (III, 8) in 1540 describes the process

briefly, but omits the poling, an essential in the production of

malleable copper.

[26] _Pompholyx_ and _spodos_ were impure zinc oxides (see note 26, p.

394).

The copper flowers were no doubt cupric oxide. They were used by the

Ancients for medicinal purposes. Dioscorides (V, 48) says: "Of flowers

of copper, which some call the scrapings of old nails, the best is

friable; it is gold-coloured when rubbed, is like millet in shape and

size, is moderately bright, and somewhat astringent. It should not be

mixed with copper filings, with which it is often adulterated. But this

deception is easily detected, for when bitten in the teeth the filings

are malleable. It (the flowers) is made when the copper fused in a

furnace has run into the receptacle through the spout pertaining to it,

for then the workmen engaged in this trade cleanse it from dirt and pour

clear water over it in order to cool it; from this sudden condensation

the copper spits and throws out the aforesaid flowers." Pliny (XXXIV,

24) says: "The flower, too, of copper (_aeris flos_) is used in medicine.

This is made by fusing copper, and then removing it to another furnace,

where the repeated blast makes the metal separate into small scales like

millet, known as flowers. These scales also fall off when the cakes of

metal are cooled in water; they become red, too, like the scales of

copper known as '_lepis_,' by use of which the flowers of copper are

adulterated, it being also sold for it. These are made when hammering

the nails that are made from the cakes of copper. All these methods are

carried on in the works of Cyprus; the difference between these

substances is that the _squamae_ (copper scales) are detached from

hammering the cakes, while the flower falls off spontaneously." Agricola

(_De Nat. Fos._, p. 352) notes that "flowers of copper (_flos aeris_)

have the same properties as 'roasted copper.'"

[27] It seems scarcely necessary to discuss in detail the complicated

"flow scheme" of the various minor bye-products. They are all

re-introduced into the liquation circuit, and thereby are created other

bye-products of the same kind _ad infinitum_. Further notes are given

on:--

Liquation thorns Note 28.

Slags " 30.

Ash-coloured copper " 29.

Concentrates " 33.

_Cadmia_ " 32.

There are no data given, either by Agricola or the later authors, which

allow satisfactory calculation of the relative quantities of these

products. A rough estimate from the data given in previous notes would

indicate that in one liquation only about 70% of the original copper

came out as refined copper, and that about 70% of the original lead

would go to the cupellation furnace, _i.e._, about 30% of the original

metal sent to the blast furnace would go into the "thorns," "slags," and

"ash-coloured copper." The ultimate losses were very great, as given

before (p. 491), they probably amounted to 25% of the silver, 9% copper,

and 16% of the lead.

[28] There were the following classes of thorns:--

1st. From liquation.

2nd. From drying.

3rd. From cupellation.

In a general way, according to the later authors, they were largely lead

oxide, and contained from 5% to 20% cuprous oxide. If a calculation be

made backward from the products given as the result of the charge

described, it would appear that in this case they must have contained at

least one-fifth copper. The silver in these liquation cakes would run

about 24 ozs. per ton, in the liquated lead about 36 ozs. per ton, and

in the liquation thorns 24 ozs. per ton. The extraction into the

liquated lead would be about 80% of the silver.

[29] The "ash-coloured copper" is a cuprous oxide, containing some 3%

lead oxide; and if Agricola means they contained two _unciae_ of silver

to the _centumpondium_, then they ran about 48 ozs. per ton, and would

contain much more silver than the mass.

[30] There are three principal "slags" mentioned--

1st. Slag from "leading."

2nd. Slag from "drying."

3rd. Slag from refining the copper.

From the analyses quoted by various authors these ran from 52% to 85%

lead oxide, 5% to 30% cuprous oxide, and considerable silica from the

furnace bottoms. They were reduced in the main into liquation cakes,

although Agricola mentions instances of the metal reduced from "slags"

being taken directly to the "drying" furnace. Such liquation cakes would

run very low in silver, and at the values given only averaged 12 ozs.

per ton; therefore the liquated lead running the same value as the

cakes, or less than half that of the "poor" lead mentioned in Note 17,

p. 512, could not have been cupelled directly.

[31] See Note 16, p. 511, for discussion of yellow and _caldarium_

copper.

[32] This _cadmia_ is given in the Glossary and the German translation

as _kobelt_. A discussion of this substance is given in the note on p.

112; and it is sufficient to state here that in Agricola's time the

metal cobalt was unknown, and the substances designated _cadmia_ and

_cobaltum_ were arsenical-cobalt-zinc minerals. A metal made from "slag"

from refining, together with "base" thorns, would be very impure; for

the latter, according to the paragraph on concentrates a little later

on, would contain the furnace accretions, and would thus be undoubtedly

zincky. It is just possible that the term _kobelt_ was used by the

German smelters at this time in the sense of an epithet--"black devil"

(see Note 21, p. 214).

[33] It is somewhat difficult to see exactly the meaning of base

(_vile_) and precious (_preciosum_) in this connection. While "base"

could mean impure, "precious" could hardly mean pure, and while

"precious" could mean high value in silver, the reverse does not seem

entirely _apropos_. It is possible that "bad" and "good" would be more

appropriate terms.

[34] The skimmings from the molten lead in the early stages of

cupellation have been discussed in Note 28, p. 539. They are probably

called thorns here because of the large amount of copper in them. The

lead from liquation would contain 2% to 3% of copper, and this would be

largely recovered in these skimmings, although there would be some

copper in the furnace bottoms--hearth-lead--and the litharge. These

"thorns" are apparently fairly rich, four _unciae_ to the

_centumpondium_ being equivalent to about 97 ozs. per ton, and they are

only added to low-grade liquation material.

[35] _Particulis aeris tusi_. Unless this be the fine concentrates from

crushing the material mentioned, we are unable to explain the

expression.

[36] This operation would bring down a button of antimony under an iron

matte, by de-sulphurizing the antimony. It would seem scarcely necessary

to add lead before cupellation. This process is given in an assay

method, in the _Probierbuechlein_ (folio 31) 50 years before _De Re

Metallica_: "How to separate silver from iron: Take that silver which is

in iron _plechen_ (_plachmal_), pulverize it finely, take the same iron

or _plec_ one part, _spiesglasz_ (antimony sulphide) one part, leave

them to melt in a crucible placed in a closed _windtofen_. When it is

melted, let it cool, break the crucible, chip off the button that is in

the bottom, and melt it in a crucible with as much lead. Then break the

crucible, and seek from the button in the cupel, and you will find what

silver it contains."

BOOK XII.

Previously I have dealt with the methods of separating silver from

copper. There now remains the portion which treats of solidified juices;

and whereas they might be considered as alien to things metallic,

nevertheless, the reasons why they should not be separated from it I

have explained in the second book.

Solidified juices are either prepared from waters in which nature or art

has infused them, or they are produced from the liquid juices

themselves, or from stony minerals. Sagacious people, at first observing

the waters of some lakes to be naturally full of juices which thickened

on being dried up by the heat of the sun and thus became solidified

juices, drew such waters into other places, or diverted them into

low-lying places adjoining hills, so that the heat of the sun should

likewise cause them to condense. Subsequently, because they observed

that in this wise the solidified juices could be made only in summer,

and then not in all countries, but only in hot and temperate regions in

which it seldom rains in summer, they boiled them in vessels over a fire

until they began to thicken. In this manner, at all times of the year,

in all regions, even the coldest, solidified juices could be obtained

from solutions of such juices, whether made by nature or by art.

Afterward, when they saw juices drip from some roasted stones, they

cooked these in pots in order to obtain solidified juices in this wise

also. It is worth the trouble to learn the proportions and the methods

by which these are made.

I will therefore begin with salt, which is made from water either salty

by nature, or by the labour of man, or else from a solution of salt, or

from lye, likewise salty. Water which is salty by nature, is condensed

and converted into salt in salt-pits by the heat of the sun, or else by

the heat of a fire in pans or pots or trenches. That which is made salty

by art, is also condensed by fire and changed into salt. There should be

as many salt-pits dug as the circumstance of the place permits, but

there should not be more made than can be used, although we ought to

make as much salt as we can sell. The depth of salt-pits should be

moderate, and the bottom should be level, so that all the water is

evaporated from the salt by the heat of the sun. The salt-pits should

first be encrusted with salt, so that they may not suck up the water.

The method of pouring or leading sea-water into salt-pits is very old,

and is still in use in many places. The method is not less old, but less

common, to pour well-water into salt-pits, as was done in Babylon, for

which Pliny is the authority, and in Cappadocia, where they used not

only well-water, but also spring-water. In all hot countries salt-water

and lake-water are conducted, poured or carried into salt-pits, and,

being dried by the heat of the sun, are converted into salt.[1] While

the salt-water contained in the salt-pits is being heated by the sun, if

they be flooded with great and frequent showers of rain the evaporation

is hindered. If this happens rarely, the salt acquires a disagreeable[2]

flavour, and in this case the salt-pits have to be filled with other

sweet water.

[Illustration 547 (Salt Pans): A--Sea. B--Pool. C--Gate. D--Trenches.

E--Salt basins. F--Rake. G--Shovel.]

Salt from sea-water is made in the following manner. Near that part of

the seashore where there is a quiet pool, and there are wide, level

plains which the inundations of the sea do not overflow, three, four,

five, or six trenches are dug six feet wide, twelve feet deep, and six

hundred feet long, or longer if the level place extends for a longer

distance; they are two hundred feet distant from one another; between

these are three transverse trenches. Then are dug the principal pits, so

that when the water has been raised from the pool it can flow into the

trenches, and from thence into the salt-pits, of which there are numbers

on the level ground between the trenches. The salt-pits are basins dug

to a moderate depth; these are banked round with the earth which was dug

in sinking them or in cleansing them, so that between the basins, earth

walls are made a foot high, which retain the water let into them. The

trenches have openings, through which the first basins receive the

water; these basins also have openings, through which the water flows

again from one into the other. There should be a slight fall, so that

the water may flow from one basin into the other, and can thus be

replenished. All these things having been done rightly and in order, the

gate is raised that opens the mouth of the pool which contains sea-water

mixed with rain-water or river-water; and thus all of the trenches are

filled. Then the gates of the first basins are opened, and thus the

remaining basins are filled with the water from the first; when this

salt-water condenses, all these basins are incrusted, and thus made

clean from earthy matter. Then again the first basins are filled up from

the nearest trench with the same kind of water, and left until much of

the thin liquid is converted into vapour by the heat of the sun and

dissipated, and the remainder is considerably thickened. Then their

gates being opened, the water passes into the second basins; and when it

has remained there for a certain space of time the gates are opened, so

that it flows into the third basins, where it is all condensed into

salt. After the salt has been taken out, the basins are filled again and

again with sea-water. The salt is raked up with wooden rakes and thrown

out with shovels.

[Illustration 549 (Salt Wells): A--Shed. B--Painted signs. C--First

room. D--Middle room. E--Third room. F--Two little windows in the end

wall. G--Third little window in the roof. H--Well. I--Well of another

kind. K--Cask. L--Pole. M--Forked sticks in which the porters rest the

pole when they are tired.]

Salt-water is also boiled in pans, placed in sheds near the wells from

which it is drawn. Each shed is usually named from some animal or other

thing which is pictured on a tablet nailed to it. The walls of these

sheds are made either from baked earth or from wicker work covered with

thick mud, although some may be made of stones or bricks. When of

brick they are often sixteen feet high, and if the roof rises

twenty-four feet high, then the walls which are at the ends must be made

forty feet high, as likewise the interior partition walls. The roof

consists of large shingles four feet long, one foot wide, and two digits

thick; these are fixed on long narrow planks placed on the rafters,

which are joined at the upper end and slope in opposite directions. The

whole of the under side is plastered one digit thick with straw mixed

with lute; likewise the roof on the outside is plastered one and a half

feet thick with straw mixed with lute, in order that the shed should not

run any risk of fire, and that it should be proof against rain, and be

able to retain the heat necessary for drying the lumps of salt. Each

shed is divided into three parts, in the first of which the firewood and

straw are placed; in the middle room, separated from the first room by a

partition, is the fireplace on which is placed the caldron. To the right

of the caldron is a tub, into which is emptied the brine brought into

the shed by the porters; to the left is a bench, on which there is room

to lay thirty pieces of salt. In the third room, which is in the back

part of the house, there is made a pile of clay or ashes eight feet

higher than the floor, being the same height as the bench. The master

and his assistants, when they carry away the lumps of salt from the

caldrons, go from the former to the latter. They ascend from the right

side of the caldron, not by steps, but by a slope of earth. At the top

of the end wall are two small windows, and a third is in the roof,

through which the smoke escapes. This smoke, emitted from both the back

and the front of the furnace, finds outlet through a hood through which

it makes its way up to the windows; this hood consists of boards

projecting one beyond the other, which are supported by two small beams

of the roof. Opposite the fireplace the middle partition has an open

door eight feet high and four feet wide, through which there is a gentle

draught which drives the smoke into the last room; the front wall also

has a door of the same height and width. Both of these doors are large

enough to permit the firewood or straw or the brine to be carried in,

and the lumps of salt to be carried out; these doors must be closed when

the wind blows, so that the boiling will not be hindered. Indeed, glass

panes which exclude the wind but transmit the light, should be inserted

in the windows in the walls.

They construct the greater part of the fireplace of rock-salt and of

clay mixed with salt and moistened with brine, for such walls are

greatly hardened by the fire. These fireplaces are made eight and a half

feet long, seven and three quarters feet wide, and, if wood is burned in

them, nearly four feet high; but if straw is burned in them, they are

six feet high. An iron rod, about four feet long, is engaged in a hole

in an iron foot, which stands on the base of the middle of the furnace

mouth. This mouth is three feet in width, and has a door which opens

inward; through it they throw in the straw.

[Illustration 551 (Salt Caldron): A--Fireplace. B--Mouth of fireplace.

C--Caldron. D--Posts sunk into the ground. E--Cross-beams. F--Shorter

bars. G--Iron hooks. H--Staples. I--Longer bars. K--Iron rod bent to

support the caldron.]

The caldrons are rectangular, eight feet long, seven feet wide, and half

a foot high, and are made of sheets of iron or lead, three feet long and

of the same width, all but two digits. These plates are not very thick,

so that the water is heated more quickly by the fire, and is boiled

away rapidly. The more salty the water is, the sooner it is condensed

into salt. To prevent the brine from leaking out at the points where the

metal plates are fastened with rivets, the caldrons are smeared over

with a cement made of ox-liver and ox-blood mixed with ashes. On each

side of the middle of the furnace two rectangular posts, three feet

long, and half a foot thick and wide are set into the ground, so that

they are distant from each other only one and a half feet. Each of them

rises one and a half feet above the caldron. After the caldron has been

placed on the walls of the furnace, two beams of the same width and

thickness as the posts, but four feet long, are laid on these posts, and

are mortised in so that they shall not fall. There rest transversely

upon these beams three bars, three feet long, three digits wide, and two

digits thick, distant from one another one foot. On each of these hang

three iron hooks, two beyond the beams and one in the middle; these are

a foot long, and are hooked at both ends, one hook turning to the right,

the other to the left. The bottom hook catches in the eye of a staple,

whose ends are fixed in the bottom of the caldron, and the eye projects

from it. There are besides, two longer bars six feet long, one palm

wide, and three digits thick, which pass under the front beam and rest

upon the rear beam. At the rear end of each of the bars there is an iron

hook two feet and three digits long, the lower end of which is bent so

as to support the caldron. The rear end of the caldron does not rest on

the two rear corners of the fireplace, but is distant from the fireplace

two thirds of a foot, so that the flame and smoke can escape; this rear

end of the fireplace is half a foot thick and half a foot higher than

the caldron. This is also the thickness and height of the wall between

the caldron and the third room of the shed, to which it is adjacent.

This back wall is made of clay and ashes, unlike the others which are

made of rock-salt. The caldron rests on the two front corners and sides

of the fireplace, and is cemented with ashes, so that the flames shall

not escape. If a dipperful of brine poured into the caldron should flow

into all the corners, the caldron is rightly set upon the fireplace.

The wooden dipper holds ten Roman _sextarii_, and the cask holds eight

dippers full[3]. The brine drawn up from the well is poured into such

casks and carried by porters, as I have said before, into the shed and

poured into a tub, and in those places where the brine is very strong it

is at once transferred with the dippers into the caldron. That brine

which is less strong is thrown into a small tub with a deep ladle, the

spoon and handle of which are hewn out of one piece of wood. In this tub

rock-salt is placed in order that the water should be made more salty,

and it is then run off through a launder which leads into the caldron.

From thirty-seven dippersful of brine the master or his deputy, at Halle

in Saxony,[4] makes two cone-shaped pieces of salt. Each master has a

helper, or in the place of a helper his wife assists him in his work,

and, in addition, a youth who throws wood or straw under the caldron.

He, on account of the great heat of the workshop, wears a straw cap on

his head and a breech cloth, being otherwise quite naked. As soon as the

master has poured the first dipperful of brine into the caldron the

youth sets fire to the wood and straw laid under it. If the firewood is

bundles of faggots or brushwood, the salt will be white, but if straw is

burned, then it is not infrequently blackish, for the sparks, which are

drawn up with the smoke into the hood, fall down again into the water

and colour it black.

[Illustration 553 (Salt Caldron): A--Wooden dipper. B--Cask. C--Tub.

D--Master. E--Youth. F--Wife. G--Wooden spade. H--Boards. I--Baskets.

K--Hoe. L--Rake. M--Straw. N--Bowl. O--Bucket containing the blood.

P--Tankard which contains beer.]

In order to accelerate the condensation of the brine, when the master

has poured in two casks and as many dippersful of brine, he adds about a

Roman _cyathus_ and a half of bullock's blood, or of calf's blood, or

buck's blood, or else he mixes it into the nineteenth dipperful of

brine, in order that it may be dissolved and distributed into all the

corners of the caldron; in other places the blood is dissolved in beer.

When the boiling water seems to be mixed with scum, he skims it with a

ladle; this scum, if he be working with rock-salt, he throws into the

opening in the furnace through which the smoke escapes, and it is dried

into rock-salt; if it be not from rock-salt, he pours it on to the floor

of the workshop. From the beginning to the boiling and skimming is the

work of half-an-hour; after this it boils down for another

quarter-of-an-hour, after which time it begins to condense into salt.

When it begins to thicken with the heat, he and his helper stir it

assiduously with a wooden spatula, and then he allows it to boil for an

hour. After this he pours in a _cyathus_ and a half of beer. In order

that the wind should not blow into the caldron, the helper covers the

front with a board seven and a half feet long and one foot high, and

covers each of the sides with boards three and three quarters feet long.

In order that the front board may hold more firmly, it is fitted into

the caldron itself, and the side-boards are fixed on the front board and

upon the transverse beam. Afterward, when the boards have been lifted

off, the helper places two baskets, two feet high and as many wide at

the top, and a palm wide at the bottom, on the transverse beams, and

into them the master throws the salt with a shovel, taking half-an-hour

to fill them. Then, replacing the boards on the caldron, he allows the

brine to boil for three quarters of an hour. Afterward the salt has

again to be removed with a shovel, and when the baskets are full, they

pile up the salt in heaps.

In different localities the salt is moulded into different shapes. In

the baskets the salt assumes the form of a cone; it is not moulded in

baskets alone, but also in moulds into which they throw the salt, which

are made in the likeness of many objects, as for instance tablets.

These tablets and cones are kept in the higher part of the third room of

the house, or else on the flat bench of the same height, in order that

they may dry better in the warm air. In the manner I have described, a

master and his helper continue one after the other, alternately boiling

the brine and moulding the salt, day and night, with the exception only

of the annual feast days. No caldron is able to stand the fire for more

than half a year. The master pours in water and washes it out every

week; when it is washed out he puts straw under it and pounds it; new

caldrons he washes three times in the first two weeks, and afterward

twice. In this manner the incrustations fall from the bottom; if they

are not cleared off, the salt would have to be made more slowly over a

fiercer fire, which requires more brine and burns the plates of the

caldron. If any cracks make their appearance in the caldron they are

filled up with cement. The salt made during the first two weeks is not

so good, being usually stained by the rust at the bottom where

incrustations have not yet adhered.

Although salt made in this manner is prepared only from the brine of

springs and wells, yet it is also possible to use this method in the

case of river-, lake-, and sea-water, and also of those waters which are

artificially salted. For in places where rock-salt is dug, the impure

and the broken pieces are thrown into fresh water, which, when boiled,

condenses into salt. Some, indeed, boil sea-salt in fresh water again,

and mould the salt into the little cones and other shapes.

[Illustration 554 (Salt Boiling): A--Pool. B--Pots. C--Ladle. D--Pans.

E--Tongs.]

Some people make salt by another method, from salt water which flows

from hot springs that issue boiling from the earth. They set earthenware

pots in a pool of the spring-water, and into them they pour water

scooped up with ladles from the hot spring until they are half full. The

perpetual heat of the waters of the pool evaporates the salt water just

as the heat of the fire does in the caldrons. As soon as it begins to

thicken, which happens when it has been reduced by boiling to a third or

more, they seize the pots with tongs and pour the contents into small

rectangular iron pans, which have also been placed in the pool. The

interior of these pans is usually three feet long, two feet wide, and

three digits deep, and they stand on four heavy legs, so that the water

flows freely all round, but not into them. Since the water flows

continuously from the pool through the little canals, and the spring

always provides a new and copious supply, always boiling hot, it

condenses the thickened water poured into the pans into salt; this is at

once taken out with shovels, and then the work begins all over again. If

the salty water contains other juices, as is usually the case with hot

springs, no salt should be made from them.

[Illustration 555 (Salt Boiling): A--Pots. B--Tripod. C--Deep ladle.]

Others boil salt water, and especially sea-water, in large iron pots;

this salt is blackish, for in most cases they burn straw under them.

Some people boil in these pots the brine in which fish is pickled. The

salt which they make tastes and smells of fish.

[Illustration 556 (Salt evaporated on faggots): A--Trench. B--Vat into

which the salt water flows. C--Ladle. D--Small bucket with pole fastened

into it.]

Those who make salt by pouring brine over firewood, lay the wood in

trenches which are twelve feet long, seven feet wide, and two and one

half feet deep, so that the water poured in should not flow out. These

trenches are constructed of rock-salt wherever it is to be had, in order

that they should not soak up the water, and so that the earth should not

fall in on the front, back and sides. As the charcoal is turned into

salt at the same time as the salt liquor, the Spaniards think, as

Pliny writes[5], that the wood itself turns into salt. Oak is the best

wood, as its pure ash yields salt; elsewhere hazel-wood is lauded. But

with whatever wood it be made, this salt is not greatly appreciated,

being black and not quite pure; on that account this method of

salt-making is disdained by the Germans and Spaniards.

[Illustration 557 (Lye Making): A--Large vat. B--Plug. C--Small tub.

D--Deep ladle. E--Small vat. F--Caldron.]

The solutions from which salt is made are prepared from salty earth or

from earth rich in salt and saltpetre. Lye is made from the ashes of

reeds and rushes. The solution obtained from salty earth by boiling,

makes salt only; from the other, of which I will speak more a little

later, salt and saltpetre are made; and from ashes is derived lye, from

which its own salt is obtained. The ashes, as well as the earth, should

first be put into a large vat; then fresh water should be poured over

the ashes or earth, and it should be stirred for about twelve hours with

a stick, so that it may dissolve the salt. Then the plug is pulled out

of the large vat; the solution of salt or the lye is drained into a

small tub and emptied with ladles into small vats; finally, such a

solution is transferred into iron or lead caldrons and boiled, until the

water having evaporated, the juices are condensed into salt. The above

are the various methods for making salt. (Illustration p. 557.)

[Illustration 559 (Nitrum-pits): A--Nile. B--Nitrum-pits, such as I

conjecture them to be.[7]]

_Nitrum_[6] is usually made from _nitrous_ waters, or from solutions or

from lye. In the same manner as sea-water or salt-water is poured into

salt-pits and evaporated by the heat of the sun and changed into salt,

so the _nitrous_ Nile is led into _nitrum_ pits and evaporated by the

heat of the sun and converted into _nitrum_. Just as the sea, in

flowing of its own will over the soil of this same Egypt, is changed

into salt, so also the Nile, when it overflows in the dog days, is

converted into _nitrum_ when it flows into the _nitrum_ pits. The

solution from which _nitrum_ is produced is obtained from fresh water

percolating through _nitrous_ earth, in the same manner as lye is made

from fresh water percolating through ashes of oak or hard oak. Both

solutions are taken out of vats and poured into rectangular copper

caldrons, and are boiled until at last they condense into _nitrum_.

[Illustration 561 (Soda Making): A--Vat in which the soda is mixed.

B--Caldron. C--Tub in which _chrysocolla_ is condensed. D--Copper wires.

E--Mortar.]

Native as well as manufactured _nitrum_ is mixed in vats with urine and

boiled in the same caldrons; the decoction is poured into vats in which

are copper wires, and, adhering to them, it hardens and becomes

_chrysocolla_, which the Moors call _borax_. Formerly _nitrum_ was

compounded with Cyprian verdigris, and ground with Cyprian copper in

Cyprian mortars, as Pliny writes. Some _chrysocolla_ is made of

rock-alum and sal-ammoniac.[8]

[Illustration 563 (Saltpetre Making): A--Caldron. B--Large vat into

which sand is thrown. C--Plug. D--Tub. E--Vat containing the rods.]

Saltpetre[9] is made from a dry, slightly fatty earth, which, if it be

retained for a while in the mouth, has an acrid and salty taste. This

earth, together with a powder, are alternately put into a vat in layers

a palm deep. The powder consists of two parts of unslaked lime and three

parts of ashes of oak, or holmoak, or Italian oak, or Turkey oak, or of

some similar kind. Each vat is filled with alternate layers of these to

within three-quarters of a foot of the top, and then water is poured in

until it is full. As the water percolates through the material it

dissolves the saltpetre; then, the plug being pulled out from the vat,

the solution is drained into a tub and ladled out into small vats. If

when tested it tastes very salty, and at the same time acrid, it is

good; but, if not, then it is condemned, and it must be made to

percolate again through the same material or through a fresh lot. Even

two or three waters may be made to percolate through the same earth and

become full of saltpetre, but the solutions thus obtained must not be

mixed together unless all have the same taste, which rarely or never

happens. The first of these solutions is poured into the first vat, the

next into the second, the third into the third vat; the second and third

solutions are used instead of plain water to percolate through fresh

material; the first solution is made in this manner from both the second

and third. As soon as there is an abundance of this solution it is

poured into the rectangular copper caldron and evaporated to one half by

boiling; then it is transferred into a vat covered with a lid, in which

the earthy matter settles to the bottom. When the solution is clear it

is poured back into the same pan, or into another, and re-boiled. When

it bubbles and forms a scum, in order that it should not run over and

that it may be greatly purified, there is poured into it three or four

pounds of lye, made from three parts of oak or similar ash and one of

unslaked lime. But in the water, prior to its being poured in, is

dissolved rock-alum, in the proportion of one hundred and twenty

_librae_ of the former to five _librae_ of the latter. Shortly

afterward the solution will be found to be clear and blue. It is boiled

until the waters, which are easily volatile (_subtiles_), are

evaporated, and then the greater part of the salt, after it has settled

at the bottom of the pan, is taken out with iron ladles. Then the

concentrated solution is transferred to the vat in which rods are placed

horizontally and vertically, to which it adheres when cold, and if there

be much, it is condensed in three or four days into saltpetre. Then the

solution which has not congealed, is poured out and put on one side or

re-boiled. The saltpetre being cut out and washed with its own solution,

is thrown on to boards that it may drain and dry. The yield of saltpetre

will be much or little in proportion to whether the solution has

absorbed much or little; when the saltpetre has been obtained from lye,

which purifies itself, it is somewhat clear and pure.

The purest and most transparent, because free from salt, is made if it

is drawn off at the thickening stage, according to the following method.

There are poured into the caldron the same number of _amphorae_ of the

solution as of _congii_ of the lye of which I have already spoken, and

into the same caldron is thrown as much of the already made saltpetre as

the solution and lye will dissolve. As soon as the mixture effervesces

and forms scum, it is transferred to a vat, into which on a cloth has

been thrown washed sand obtained from a river. Soon afterward the plug

is drawn out of the hole at the bottom, and the mixture, having

percolated through the sand, escapes into a tub. It is then reduced by

boiling in one or another of the caldrons, until the greater part of the

solution has evaporated; but as soon as it is well boiled and forms

scum, a little lye is poured into it. Then it is transferred to another

vat in which there are small rods, to which it adheres and congeals in

two days if there is but little of it, or if there is much in three

days, or at the most in four days; if it does not condense, it is poured

back into the caldron and re-boiled down to half; then it is transferred

to the vat to cool. The process must be repeated as often as is

necessary.

Others refine saltpetre by another method, for with it they fill a pot

made of copper, and, covering it with a copper lid, set it over live

coals, where it is heated until it melts. They do not cement down the

lid, but it has a handle, and can be lifted for them to see whether or

not the melting has taken place. When it has melted, powdered sulphur is

sprinkled in, and if the pot set on the fire does not light it, the

sulphur kindles, whereby the thick, greasy matter floating on the

saltpetre burns up, and when it is consumed the saltpetre is pure. Soon

afterward the pot is removed from the fire, and later, when cold, the

purest saltpetre is taken out, which has the appearance of white marble,

the earthy residue then remains at the bottom. The earths from which the

solution was made, together with branches of oak or similar trees, are

exposed under the open sky and sprinkled with water containing

saltpetre. After remaining thus for five or six years, they are again

ready to be made into a solution.

Pure saltpetre which has rested many years in the earth, and that which

exudes from the stone walls of wine cellars and dark places, is mixed

with the first solution and evaporated by boiling.

Thus far I have described the methods of making _nitrum_, which are not

less varied or multifarious than those for making salt. Now I propose to

describe the methods of making alum,[10] which are likewise neither all

alike, nor simple, because it is made from boiling aluminous water until

it condenses to alum, or else from boiling a solution of alum which is

obtained from a kind of earth, or from rocks, or from pyrites, or other

minerals.

[Illustration 567 (Vitriol Making): A--Tanks. B--Stirring poles.

C--Plug. D--Trough. E--Reservoir. F--Launder. G--lead caldron. H--Wooden

tubs sunk into the earth. I--Vats in which twigs are fixed.]

This kind of earth having first been dug up in such quantity as would

make three hundred wheelbarrow loads, is thrown into two tanks; then the

water is turned into them, and if it (the earth) contains vitriol it

must be diluted with urine. The workmen must many times a day stir the

ore with long, thick sticks in order that the water and urine may be

mixed with it; then the plugs having been taken out of both tanks, the

solution is drawn off into a trough, which is carved out of one or two

trees. If the locality is supplied with an abundance of such ore, it

should not immediately be thrown into the tanks, but first conveyed into

open spaces and heaped up, for the longer it is exposed to the air and

the rain, the better it is; after some months, during which the ore has

been heaped up in open spaces into mounds, there are generated veinlets

of far better quality than the ore. Then it is conveyed into six or more

tanks, nine feet in length and breadth and five in depth, and afterward

water is drawn into them of similar solution. After this, when the water

has absorbed the alum, the plugs are pulled out, and the solution

escapes into a round reservoir forty feet wide and three feet deep. Then

the ore is thrown out of the tanks into other tanks, and water again

being run into the latter and the urine added and stirred by means of

poles, the plugs are withdrawn and the solution is run off into the same

reservoir. A few days afterward, the reservoirs containing the solution

are emptied through a small launder, and run into rectangular lead

caldrons; it is boiled in them until the greater part of the water has

evaporated. The earthy sediment deposited at the bottom of the caldron

is composed of fatty and aluminous matter, which usually consists of

small incrustations, in which there is not infrequently found a very

white and very light powder of asbestos or gypsum. The solution now

seems to be full of meal. Some people instead pour the partly evaporated

solution into a vat, so that it may become pure and clear; then pouring

it back into the caldron, they boil it again until it becomes mealy. By

whichever process it has been condensed, it is then poured into a wooden

tub sunk into the earth in order to cool it. When it becomes cold it is

poured into vats, in which are arranged horizontal and vertical twigs,

to which the alum clings when it condenses; and thus are made the small

white transparent cubes, which are laid to dry in hot rooms.

If vitriol forms part of the aluminous ore, the material is dissolved in

water without being mixed with urine, but it is necessary to pour that

into the clear and pure solution when it is to be re-boiled. This

separates the vitriol from the alum, for by this method the latter sinks

to the bottom of the caldron, while the former floats on the top; both

must be poured separately into smaller vessels, and from these into vats

to condense. If, however, when the solution was re-boiled they did not

separate, then they must be poured from the smaller vessels into larger

vessels and covered over; then the vitriol separating from the alum, it

condenses. Both are cut out and put to dry in the hot room, and are

ready to be sold; the solution which did not congeal in the vessels

and vats is again poured back into the caldron to be re-boiled. The

earth which settled at the bottom of the caldron is carried back to the

tanks, and, together with the ore, is again dissolved with water and

urine. The earth which remains in the tanks after the solution has been

drawn off is emptied in a heap, and daily becomes more and more

aluminous in the same way as the earth from which saltpetre was made,

but fuller of its juices, wherefore it is again thrown into the tanks

and percolated by water.

[Illustration 571 (Alum Making): A--Furnace. B--Enclosed space.

C--Aluminous rock. D--Deep ladle. E--Caldron. F--Launder. G--Troughs.]

Aluminous rock is first roasted in a furnace similar to a lime kiln. At

the bottom of the kiln a vaulted fireplace is made of the same kind of

rock; the remainder of the empty part of the kiln is then entirely

filled with the same aluminous rocks. Then they are heated with fire

until they are red hot and have exhaled their sulphurous fumes, which

occurs, according to their divers nature, within the space of ten,

eleven, twelve, or more hours. One thing the master must guard against

most of all is not to roast the rock either too much or too little, for

on the one hand they would not soften when sprinkled with water, and on

the other they either would be too hard or would crumble into ashes;

from neither would much alum be obtained, for the strength which they

have would be decreased. When the rocks are cooled they are drawn out

and conveyed into an open space, where they are piled one upon the other

in heaps fifty feet long, eight feet wide, and four feet high, which are

sprinkled for forty days with water carried in deep ladles. In spring

the sprinkling is done both morning and evening, and in summer at noon

besides. After being moistened for this length of time the rocks begin

to fall to pieces like slaked lime, and there originates a certain new

material of the future alum, which is soft and similar to the _liquidae

medullae_ found in the rocks. It is white if the stone was white before

it was roasted, and rose-coloured if red was mixed with the white; from

the former, white alum is obtained, and from the latter, rose-coloured.

A round furnace is made, the lower part of which, in order to be able to

endure the force of the heat, is made of rock that neither melts nor

crumbles to powder by the fire. It is constructed in the form of a

basket, the walls of which are two feet high, made of the same rock. On

these walls rests a large round caldron made of copper plates, which is

concave at the bottom, where it is eight feet in diameter. In the empty

space under the bottom they place the wood to be kindled with fire.

Around the edge of the bottom of the caldron, rock is built in

cone-shaped, and the diameter of the bottom of the rock structure is

seven feet, and of the top ten feet; it is eight feet deep. The inside,

after being rubbed over with oil, is covered with cement, so that it may

be able to hold boiling water; the cement is composed of fresh lime, of

which the lumps are slaked with wine, of iron-scales, and of sea-snails,

ground and mixed with the white of eggs and oil. The edges of the

caldron are surmounted with a circle of wood a foot thick and half a

foot high, on which the workmen rest the wooden shovels with which they

cleanse the water of earth and of the undissolved lumps of rock that

remain at the bottom of the caldron. The caldron, being thus prepared,

is entirely filled through a launder with water, and this is boiled with

a fierce fire until it bubbles. Then little by little eight wheelbarrow

loads of the material, composed of roasted rock moistened with water,

are gradually emptied into the caldron by four workmen, who, with their

shovels which reach to the bottom, keep the material stirred and mixed

with water, and by the same means they lift the lumps of undissolved

rock out of the caldron. In this manner the material is thrown in, in

three or four lots, at intervals of two or three hours more or less;

during these intervals, the water, which has been cooled by the rock and

material, again begins to boil. The water, when sufficiently purified

and ready to congeal, is ladled out and run off with launders into

thirty troughs. These troughs are made of oak, holm oak, or Turkey oak;

their interior is six feet long, five feet deep, and four feet wide. In

these the water congeals and condenses into alum, in the spring in the

space of four days, and in summer in six days. Afterward the holes at

the bottom of the oak troughs being opened, the water which has not

congealed is drawn off into buckets and poured back into the caldron; or

it may be preserved in empty troughs, so that the master of the workmen,

having seen it, may order his helpers to pour it into the caldron, for

the water which is not altogether wanting in alum, is considered better

than that which has none at all. Then the alum is hewn out with a knife

or a chisel. It is thick and excellent according to the strength of the

rock, either white or pink according to the colour of the rock. The

earthy powder, which remains three to four digits thick as the residue

of the alum at the bottom of the trough is again thrown into the caldron

and boiled with fresh aluminous material. Lastly, the alum cut out is

washed, and dried, and sold.

Alum is also made from crude pyrites and other aluminous mixtures. It is

first roasted in an enclosed area; then, after being exposed for some

months to the air in order to soften it, it is thrown into vats and

dissolved. After this the solution is poured into the leaden rectangular

pans and boiled until it condenses into alum. The pyrites and other

stones which are not mixed with alum alone, but which also contain

vitriol, as is most usually the case, are both treated in the manner

which I have already described. Finally, if metal is contained in the

pyrites and other rock, this material must be dried, and from it either

gold, silver, or copper is made in a furnace.

Vitriol[11] can be made by four different methods; by two of these

methods from water containing vitriol; by one method from a solution of

_melanteria_, _sory_ and _chalcitis_; and by another method from earth

or stones mixed with vitriol.

[Illustration 574 (Vitriol Making): A--Tunnel. B--Bucket. C--Pit.]

The vitriol water is collected into pools, and if it cannot be drained

into them, it must be drawn up and carried to them in buckets by a

workman. In hot regions or in summer, it is poured into out-of-door

pits which have been dug to a certain depth, or else it is extracted

from shafts by pumps and poured into launders, through which it flows

into the pits, where it is condensed by the heat of the sun. In cold

regions and in winter these vitriol waters are boiled down with equal

parts of fresh water in rectangular leaden caldrons; then, when cold,

the mixture is poured into vats or into tanks, which Pliny calls wooden

fish-tanks. In these tanks light cross-beams are fixed to the upper

part, so that they may be stationary, and from them hang ropes stretched

with little stones; to these the contents of the thickened solutions

congeal and adhere in transparent cubes or seeds of vitriol, like

bunches of grapes.

[Illustration 575 (Vitriol Making): A--Caldron. B--Tank. C--Cross-bars.

D--Ropes. E--Little stones.]

By the third method vitriol is made out of _melanteria_ and _sory_. If

the mines give an abundant supply of _melanteria_ and _sory_, it is

better to reject the _chalcitis_, and especially the _misy_, for from

these the vitriol is impure, particularly from the _misy_. These

materials having been dug and thrown into the tanks, they are first

dissolved with water; then, in order to recover the pyrites from which

copper is not rarely smelted and which forms a sediment at the bottom of

the tanks, the solution is transferred to other vats, which are nine

feet wide and three feet deep. Twigs and wood which float on the surface

are lifted out with a broom made of twigs, and afterward all the

sediment settles at the bottom of this vat. The solution is poured into

a rectangular leaden caldron eight feet long, three feet wide, and the

same in depth. In this caldron it is boiled until it becomes thick and

viscous, when it is poured into a launder, through which it runs into

another leaden caldron of the same size as the one described before.

When cold, the solution is drawn off through twelve little launders, out

of which it flows into as many wooden tubs four and a half feet deep and

three feet wide. Upon these tubs are placed perforated crossbars distant

from each other from four to six digits, and from the holes hang thin

laths, which reach to the bottom, with pegs or wedges driven into them.

The vitriol adheres to these laths, and within the space of a few days

congeals into cubes, which are taken away and put into a chamber having

a sloping board floor, so that the moisture which drips from the vitriol

may flow into a tub beneath. This solution is re-boiled, as is also that

solution which was left in the twelve tubs, for, by reason of its having

become too thin and liquid, it did not congeal, and was thus not

converted into vitriol.

[Illustration 576 (Vitriol Making): A--Wooden tub. B--Cross-bars.

C--Laths. D--Sloping floor of the chamber. E--Tub placed under it.]

[Illustration 577 (Vitriol Making): A--Caldron. B--Moulds. C--Cakes.]

The fourth method of making vitriol is from vitriolous earth or stones.

Such ore is at first carried and heaped up, and is then left for five or

six months exposed to the rain of spring and autumn, to the heat of

summer, and to the rime and frost of winter. It must be turned over

several times with shovels, so that the part at the bottom may be

brought to the top, and it is thus ventilated and cooled; by this means

the earth crumbles up and loosens, and the stone changes from hard to

soft. Then the ore is covered with a roof, or else it is taken away and

placed under a roof, and remains in that place six, seven, or eight

months. Afterward as large a portion as is required is thrown into a

vat, which is half-filled with water; this vat is one hundred feet

long, twenty-four feet wide, eight feet deep. It has an opening at the

bottom, so that when it is opened the dregs of the ore from which the

vitriol comes may be drawn off, and it has, at the height of one foot

from the bottom, three or four little holes, so that, when closed, the

water may be retained, and when opened the solution flows out. Thus the

ore is mixed with water, stirred with poles and left in the tank until

the earthy portions sink to the bottom and the water absorbs the juices.

Then the little holes are opened, the solution flows out of the vat, and

is caught in a vat below it; this vat is of the same length as the

other, but twelve feet wide and four feet deep. If the solution is not

sufficiently vitriolous it is mixed with fresh ore; but if it contains

enough vitriol, and yet has not exhausted all of the ore rich in

vitriol, it is well to dissolve the ore again with fresh water. As soon

as the solution becomes clear, it is poured into the rectangular leaden

caldron through launders, and is boiled until the water is evaporated.

Afterward as many thin strips of iron as the nature of the solution

requires, are thrown in, and then it is boiled again until it is thick

enough, when cold, to congeal into vitriol. Then it is poured into tanks

or vats, or any other receptacle, in which all of it that is apt to

congeal does so within two or three days. The solution which does not

congeal is either poured back into the caldron to be boiled again, or

it is put aside for dissolving the new ore, for it is far preferable to

fresh water. The solidified vitriol is hewn out, and having once more

been thrown into the caldron, is re-heated until it liquefies; when

liquid, it is poured into moulds that it may be made into cakes. If the

solution first poured out is not satisfactorily thickened, it is

condensed two or three times, and each time liquefied in the caldron and

re-poured into the moulds, in which manner pure cakes, beautiful to look

at, are made from it.

The vitriolous pyrites, which are to be numbered among the mixtures

(_mistura_), are roasted as in the case of alum, and dissolved with

water, and the solution is boiled in leaden caldrons until it condenses

into vitriol. Both alum and vitriol are often made out of these, and it

is no wonder, for these juices are cognate, and only differ in the one

point,--that the former is less, the latter more, earthy. That pyrites

which contains metal must be smelted in the furnace. In the same manner,

from other mixtures of vitriolic and metalliferous material are made

vitriol and metal. Indeed, if ores of vitriolous pyrites abound, the

miners split small logs down the centre and cut them off in lengths as

long as the drifts and tunnels are wide, in which they lay them down

transversely; but, that they may be stable, they are laid on the ground

with the wide side down and the round side up, and they touch each other

at the bottom, but not at the top. The intermediate space is filled with

pyrites, and the same crushed are scattered over the wood, so that,

coming in or going out, the road is flat and even. Since the drifts or

tunnels drip with water, these pyrites are soaked, and from them are

freed the vitriol and cognate things. If the water ceases to drip, these

dry and harden, and then they are raised from the shafts, together with

the pyrites not yet dissolved in the water, or they are carried out from

the tunnels; then they are thrown into vats or tanks, and boiling water

having been poured over them, the vitriol is freed and the pyrites are

dissolved. This green solution is transferred to other vats or tanks,

that it may be made clear and pure; it is then boiled in the lead

caldrons until it thickens; afterward it is poured into wooden tubs,

where it condenses on rods, or reeds, or twigs, into green vitriol.

Sulphur is made from sulphurous waters, from sulphurous ores, and from

sulphurous mixtures. These waters are poured into the leaden caldrons

and boiled until they condense into sulphur. From this latter, heated

together with iron-scales, and transferred into pots, which are

afterward covered with lute and refined sulphur, another sulphur is

made, which we call _caballinum_.[12]

[Illustration 579 (Sulphur Making): A--Pots having spouts. B--Pots

without spouts. C--Lids.]

The ores[13] which consist mostly of sulphur and of earth, and rarely of

other minerals, are melted in big-bellied earthenware pots. The

furnaces, which hold two of these pots, are divided into three parts;

the lowest part is a foot high, and has an opening at the front for the

draught; the top of this is covered with iron plates, which are

perforated near the edges, and these support iron rods, upon which the

firewood is placed. The middle part of the furnace is one and a half

feet high, and has a mouth in front, so that the wood may be inserted;

the top of this has rods, upon which the bottom of the pots stand. The

upper part is about two feet high, and the pots are also two feet high

and one digit thick; these have below their mouths a long, slender

spout. In order that the mouth of the pot may be covered, an earthenware

lid is made which fits into it. For every two of these pots there must

be one pot of the same size and shape, and without a spout, but having

three holes, two of which are below the mouth and receive the spouts of

the two first pots; the third hole is on the opposite side at the

bottom, and through it the sulphur flows out. In each furnace are placed

two pots with spouts, and the furnace must be covered by plates of iron

smeared over with lute two digits thick; it is thus entirely closed in,

but for two or three vent-holes through which the mouths of the pots

project. Outside of the furnace, against one side, is placed the pot

without a spout, into the two holes of which the two spouts of the other

pots penetrate, and this pot should be built in at both sides to keep it

steady. When the sulphur ore has been placed in the pots, and these

placed in the furnace, they are closely covered, and it is desirable to

smear the joint over with lute, so that the sulphur will not exhale, and

for the same reason the pot below is covered with a lid, which is also

smeared with lute. The wood having been kindled, the ores are heated

until the sulphur is exhaled, and the vapour, arising through the spout,

penetrates into the lower pot and thickens into sulphur, which falls to

the bottom like melted wax. It then flows out through the hole, which,

as I said, is at the bottom of this pot; and the workman makes it into

cakes, or thin sticks or thin pieces of wood are dipped in it. Then he

takes the burning wood and glowing charcoal from the furnace, and when

it has cooled, he opens the two pots, empties the residues, which, if

the ores were composed of sulphur and earth, resemble naturally

extinguished ashes; but if the ores consisted of sulphur and earth and

stone, or sulphur and stone only, they resemble earth completely dried

or stones well roasted. Afterward the pots are re-filled with ore, and

the whole work is repeated.

[Illustration 581 (Sulphur Making): A--Long wall. B--High walls. C--Low

walls. D--Plates. E--Upper pots. F--Lower pots.]

The sulphurous mixture, whether it consists of stone and sulphur only,

or of stone and sulphur and metal, may be heated in similar pots, but

with perforated bottoms. Before the furnace is constructed, against the

"second" wall of the works two lateral partitions are built seven feet

high, three feet long, one and a half feet thick, and these are distant

from each other twenty-seven feet. Between them are seven low brick

walls, that measure but two feet and the same number of digits in

height, and, like the other walls, are three feet long and one foot

thick; these little walls are at equal distances from one another,

consequently they will be two and one half feet apart. At the top, iron

bars are fixed into them, which sustain iron plates three feet long and

wide and one digit thick, so that they can bear not only the weight of

the pots, but also the fierceness of the fire. These plates have in the

middle a round hole one and a half digits wide; there must not be more

than eight of these, and upon them as many pots are placed. These pots

are perforated at the bottom, and the same number of whole pots are

placed underneath them; the former contain the mixture, and are covered

with lids; the latter contain water, and their mouths are under the

holes in the plates. After wood has been arranged round the upper pots

and ignited, the mixture being heated, red, yellow, or green sulphur

drips from it and flows down through the hole, and is caught by the pots

placed underneath the plates, and is at once cooled by the water. If the

mixture contains metal, it is reserved for smelting, and, if not, it is

thrown away. The sulphur from such a mixture can best be extracted if

the upper pots are placed in a vaulted furnace, like those which I

described among other metallurgical subjects in Book VIII., which has no

floor, but a grate inside; under this the lower pots are placed in the

same manner, but the plates must have larger holes.

[Illustration 582 (Bitumen Making): A--Lower pot. B--Upper pot. C--Lid.]

Others bury a pot in the ground, and place over it another pot with a

hole at the bottom, in which pyrites or _cadmia_, or other sulphurous

stones are so enclosed that the sulphur cannot exhale. A fierce fire

heats the sulphur, and it drips away and flows down into the lower pot,

which contains water. (Illustration p. 582).

[Illustration 583 (Bitumen Making): A--Bituminous spring. B--Bucket.

C--Pot. D--Lid.]

Bitumen[14] is made from bituminous waters, from liquid bitumen, and

from mixtures of bituminous substances. The water, bituminous as well as

salty, at Babylon, as Pliny writes, was taken from the wells to the

salt works and heated by the great heat of the sun, and condensed partly

into liquid bitumen and partly into salt. The bitumen being lighter,

floats on the top, while the salt being heavier, sinks to the bottom.

Liquid bitumen, if there is much floating on springs, streams and

rivers, is drawn up in buckets or other vessels; but, if there is

little, it is collected with goose wings, pieces of linen, _ralla_,

shreds of reeds, and other things to which it easily adheres, and it is

boiled in large brass or iron pots by fire and condensed. As this

bitumen is put to divers uses, some mix pitch with the liquid, others

old cart-grease, in order to temper its viscosity; these, however long

they are boiled in the pots, cannot be made hard. The mixtures

containing bitumen are also treated in the same manner as those

containing sulphur, in pots having a hole in the bottom, and it is rare

that such bitumen is not highly esteemed.

[Illustration 585 (Chrysocolla Making): A--Mouth of the tunnel.

B--Trough. C--Tanks. D--Little trough.]

Since all solidified juices and earths, if abundantly and copiously

mixed with the water, are deposited in the beds of springs, streams or

rivers, and the stones therein are coated by them, they do not require

the heat of the sun or fire to harden them. This having been pondered

over by wise men, they discovered methods by which the remainder of

these solidified juices and unusual earths can be collected. Such

waters, whether flowing from springs or tunnels, are collected in many

wooden tubs or tanks arranged in consecutive order, and deposit in them

such juices or earths; these being scraped off every year, are

collected, as _chrysocolla_[15] in the Carpathians and as ochre in the

Harz.

There remains glass, the preparation of which belongs here, for the

reason that it is obtained by the power of fire and subtle art from

certain solidified juices and from coarse or fine sand. It is

transparent, as are certain solidified juices, gems, and stones; and can

be melted like fusible stones and metals. First I must speak of the

materials from which glass is made; then of the furnaces in which it is

melted; then of the methods by which it is produced.

It is made from fusible stones and from solidified juices, or from other

juicy substances which are connected by a natural relationship. Stones

which are fusible, if they are white and translucent, are more excellent

than the others, for which reason crystals take the first place. From

these, when pounded, the most excellent transparent glass was made in

India, with which no other could be compared, as Pliny relates. The

second place is accorded to stones which, although not so hard as

crystal, are yet just as white and transparent. The third is given to

white stones, which are not transparent. It is necessary, however, first

of all to heat all these, and afterward they are subjected to the pestle

in order to break and crush them into coarse sand, and then they are

passed through a sieve. If this kind of coarse or fine sand is found by

the glass-makers near the mouth of a river, it saves them much labour in

burning and crushing. As regards the solidified juices, the first place

is given to soda; the second to white and translucent rock-salt; the

third to salts which are made from lye, from the ashes of the musk ivy,

or from other salty herbs. Yet there are some who give to this latter,

and not to the former, the second place. One part of coarse or fine sand

made from fusible stones should be mixed with two parts of soda or of

rock-salt or of herb salts, to which are added minute particles of

_magnes_.[16] It is true that in our day, as much as in ancient times,

there exists the belief in the singular power of the latter to attract

to itself the vitreous liquid just as it does iron, and by attracting it

to purify and transform green or yellow into white; and afterward fire

consumes the _magnes_. When the said juices are not to be had, two parts

of the ashes of oak or holmoak, or of hard oak or Turkey oak, or if

these be not available, of beech or pine, are mixed with one part of

coarse or fine sand, and a small quantity of salt is added, made from

salt water or sea-water, and a small particle of _magnes_; but these

make a less white and translucent glass. The ashes should be made from

old trees, of which the trunk at a height of six feet is hollowed out

and fire is put in, and thus the whole tree is consumed and converted

into ashes. This is done in winter when the snow lies long, or in summer

when it does not rain, for the showers at other times of the year, by

mixing the ashes with earth, render them impure; for this reason, at

such times, these same trees are cut up into many pieces and burned

under cover, and are thus converted into ashes.

[Illustration 587 (Glass-making Furnace): A--Lower chamber of the first

furnace. B--Upper chamber. C--Vitreous mass.]

Some glass-makers use three furnaces, others two, others only one. Those

who use three, melt the material in the first, re-melt it in the second,

and in the third they cool the glowing glass vessels and other

articles. Of these the first furnace must be vaulted and similar to an

oven. In the upper chamber, which is six feet long, four feet wide, and

two feet high, the mixed materials are heated by a fierce fire of dry

wood until they melt and are converted into a vitreous mass. And if they

are not satisfactorily purified from dross, they are taken out and

cooled and broken into pieces; and the vitreous pieces are heated in

pots in the same furnace.

[Illustration 588 (Glass-making Furnace): A--Arches of the second

furnace. B--Mouth of the lower chamber. C--Windows of the upper chamber.

D--Big-bellied pots. E--Mouth of the third furnace. F--Recesses for the

receptacles. G--Openings in the upper chamber. H--Oblong receptacles.]

The second furnace is round, ten feet in diameter and eight feet high,

and on the outside, so that it may be stronger, it is encompassed by

five arches, one and one half feet thick; it consists in like manner of

two chambers, of which the lower one is vaulted and is one and one half

feet thick. In front this chamber has a narrow mouth, through which the

wood can be put into the hearth, which is on the ground. At the top and

in the middle of its vault, there is a large round hole which opens to

the upper chamber, so that the flames can penetrate into it. Between the

arches in the walls of the upper chamber are eight windows, so large

that the big-bellied pots may be placed through them on to the floor of

the chamber, around the large hole. The thickness of these pots is about

two digits, their height the same number of feet, and the diameter of

the belly one and a half feet, and of the mouth and bottom one foot. In

the back part of the furnace is a rectangular hole, measuring in height

and width a palm, through which the heat penetrates into a third furnace

which adjoins it.

This third furnace is rectangular, eight feet long and six feet wide; it

also consists of two chambers, of which the lower has a mouth in front,

so that firewood may be placed on the hearth which is on the ground. On

each side of this opening in the wall of the lower chamber is a recess

for oblong earthenware receptacles, which are about four feet long, two

feet high, and one and a half feet wide. The upper chamber has two

holes, one on the right side, the other on the left, of such height and

width that earthenware receptacles may be conveniently placed in them.

These latter receptacles are three feet long, one and a half feet high,

the lower part one foot wide, and the upper part rounded. In these

receptacles the glass articles, which have been blown, are placed so

that they may cool in a milder temperature; if they were not cooled

slowly they would burst asunder. When the vessels are taken from the

upper chamber, they are immediately placed in the receptacles to cool.

[Illustration 589 (Glass-making Furnaces): A--Lower chamber of the

other second furnace. B--Middle one. C--Upper one. D--Its opening.

E--Round opening. F--Rectangular opening.]

Some who use two furnaces partly melt the mixture in the first, and not

only re-melt it in the second, but also replace the glass articles

there. Others partly melt and re-melt the material in different chambers

of the second furnace. Thus the former lack the third furnace, and the

latter, the first. But this kind of second furnace differs from the

other second furnace, for it is, indeed, round, but the interior is

eight feet in diameter and twelve feet high, and it consists of three

chambers, of which the lowest is not unlike the lowest of the other

second furnace. In the middle chamber wall there are six arched

openings, in which are placed the pots to be heated, and the remainder

of the small windows are blocked up with lute. In the middle top of the

middle chamber is a square opening a palm in length and width. Through

this the heat penetrates into the upper chamber, of which the rear part

has an opening to receive the oblong earthenware receptacles, in which

are placed the glass articles to be slowly cooled. On this side, the

ground of the workshop is higher, or else a bench is placed there, so

that the glass-makers may stand upon it to stow away their products more

conveniently.

Those who lack the first furnace in the evening, when they have

accomplished their day's work, place the material in the pots, so that

the heat during the night may melt it and turn it into glass. Two boys

alternately, during night and day, keep up the fire by throwing dry wood

on to the hearth. Those who have but one furnace use the second sort,

made with three chambers. Then in the evening they pour the material

into the pots, and in the morning, having extracted the fused material,

they make the glass objects, which they place in the upper chamber, as

do the others.

The second furnace consists either of two or three chambers, the first

of which is made of unburnt bricks dried in the sun. These bricks are

made of a kind of clay that cannot be easily melted by fire nor resolved

into powder; this clay is cleaned of small stones and beaten with rods.

The bricks are laid with the same kind of clay instead of lime. From the

same clay the potters also make their vessels and pots, which they dry

in the shade. These two parts having been completed, there remains the

third.

[Illustration 591 (Glass Making): A--Blow-pipe. B--Little window.

C--Marble. D--Forceps. E--Moulds by means of which the shapes are

produced.]

The vitreous mass having been made in the first furnace in the manner I

described, is broken up, and the assistant heats the second furnace, in

order that the fragments may be re-melted. In the meantime, while they

are doing this, the pots are first warmed by a slow fire in the first

furnace, so that the vapours may evaporate, and then by a fiercer fire,

so that they become red in drying. Afterward the glass-makers open the

mouth of the furnace, and, seizing the pots with tongs, if they have not

cracked and fallen to pieces, quickly place them in the second furnace,

and they fill them up with the fragments of the heated vitreous mass or

with glass. Afterward they close up all the windows with lute and

bricks, with the exception that in each there are two little windows

left free; through one of these they inspect the glass contained in the

pot, and take it up by means of a blow-pipe; in the other they rest

another blow-pipe, so that it may get warm. Whether it is made of brass,

bronze, or iron, the blow-pipe must be three feet long. In front of

the window is inserted a lip of marble, on which rests the heaped-up

clay and the iron shield. The clay holds the blow-pipe when it is put

into the furnace, whereas the shield preserves the eyes of the

glass-maker from the fire. All this having been carried out in order,

the glass-makers bring the work to completion. The broken pieces they

re-melt with dry wood, which emits no smoke, but only a flame. The

longer they re-melt it, the purer and more transparent it becomes, the

fewer spots and blisters there are, and therefore the glass-makers can

carry out their work more easily. For this reason those who only melt

the material from which glass is made for one night, and then

immediately make it up into glass articles, make them less pure and

transparent than those who first produce a vitreous mass and then

re-melt the broken pieces again for a day and a night. And, again, these

make a less pure and transparent glass than do those who melt it again

for two days and two nights, for the excellence of the glass does not

consist solely in the material from which it is made, but also in the

melting. The glass-makers often test the glass by drawing it up with the

blowpipes; as soon as they observe that the fragments have been

re-melted and purified satisfactorily, each of them with another

blow-pipe which is in the pot, slowly stirs and takes up the glass which

sticks to it in the shape of a ball like a glutinous, coagulated gum. He

takes up just as much as he needs to complete the article he wishes to

make; then he presses it against the lip of marble and kneads it round

and round until it consolidates. When he blows through the pipe he blows

as he would if inflating a bubble; he blows into the blow-pipe as often

as it is necessary, removing it from his mouth to re-fill his cheeks, so

that his breath does not draw the flames into his mouth. Then, twisting

the lifted blow-pipe round his head in a circle, he makes a long glass,

or moulds the same in a hollow copper mould, turning it round and round,

then warming it again, blowing it and pressing it, he widens it into the

shape of a cup or vessel, or of any other object he has in mind. Then he

again presses this against the marble to flatten the bottom, which he

moulds in the interior with his other blow-pipe. Afterward he cuts out

the lip with shears, and, if necessary, adds feet and handles. If it so

please him, he gilds it and paints it with various colours. Finally, he

lays it in the oblong earthenware receptacle, which is placed in the

third furnace, or in the upper chamber of the second furnace, that it

may cool. When this receptacle is full of other slowly-cooled articles,

he passes a wide iron bar under it, and, carrying it on the left arm,

places it in another recess.

The glass-makers make divers things, such as goblets, cups, ewers,

flasks, dishes, plates, panes of glass, animals, trees, and ships, all

of which excellent and wonderful works I have seen when I spent two

whole years in Venice some time ago. Especially at the time of the Feast

of the Ascension they were on sale at Morano, where are located the most

celebrated glass-works. These I saw on other occasions, and when, for a

certain reason, I visited Andrea Naugerio in his house which he had

there, and conversed with him and Francisco Asulano.

END OF BOOK XII.

FOOTNOTES:

[1] The history of salt-making in salt-pans, from sea-water or salt

springs, goes further back than human records. From an historical point

of view the real interest attached to salt lies in the bearing which

localities rich in either natural salt or salt springs, have had upon

the movements of the human race. Many ancient trade routes have been due

to them, and innumerable battles have been fought for their possession.

Salt has at times served for currency, and during many centuries in

nearly every country has served as a basis of taxation. These subjects

do not, however, come within the scope of this text. For the quotation

from Pliny referred to, see Note 14 below, on bitumen.

[2] The first edition gives _graviorem_, the latter editions

_gratiorem_, which latter would have quite the reverse meaning from the

above.

[3] The following are approximately the English equivalents:--

Pints. Quarts. Gallons.

1 _Cyathus_ .08

3 _Cyathi_ = 1 _Quartarius_ .24

4 _Quartarii_ = 1 _Sextarius_ .99

6 _Sextarii_ = 1 _Congius_ 5.94 2.97

16 _Sextarii_ = 1 _Modius_ 15.85 7.93 1.98

8 _Congii_ = 1 _Amphora_ 47.57 23.78 5.94

The dipper mentioned would thus hold about one and one quarter gallons,

and the cask ten gallons.

[4] The salt industry, founded upon salt springs, is still of importance

to this city. It was a salt centre of importance to the Germanic tribes

before Charles, the son of Charlemagne, erected a fortress here in 806.

Mention of the salt works is made in the charter by Otto I., conveying

the place to the Diocese of Magdeburg, in 968.

[5] Pliny XXXI., 39-40. "In the Gallic provinces in Germany they pour

salt water upon burning wood. The Spaniards in a certain place draw the

brine from wells, which they call _Muria_. They indeed think that the

wood turns to salt, and that the oak is the best, being the kind which

is itself salty. Elsewhere the hazel is praised. Thus the charcoal even

is turned into salt when it is steeped in brine. Whenever salt is made

with wood it is black."

[6] We have elsewhere in this book used the word "soda" for the Latin

term _nitrum_, because we believe as used by Agricola it was always

soda, and because some confusion of this term with its modern adaptation

for saltpetre (nitre) might arise in the mind of the reader.

Fortunately, Agricola usually carefully mentions other alkalis, such as

the product from lixiviation of ashes, separately from his _nitrum_. In

these paragraphs, however, he has soda and potash hopelessly mixed,

wherefore we have here introduced the Latin term. The actual difference

between potash and soda--the _nitrum_ of the Ancients, and the _alkali_

of Geber (and the glossary of Agricola), was not understood for two

hundred years after Agricola, when Duhamel made his well-known

determinations; and the isolation of sodium and potassium was, of

course, still later by fifty years. If the reeds and rushes described in

this paragraph grew near the sea, the salt from lixiviation would be

soda, and likewise the Egyptian product was soda, but the lixiviation of

wood-ash produces only potash; as seen above, all are termed _nitrum_

except the first.

HISTORICAL NOTES.--The word _nitrum_, _nitron_, _nitri_, _neter_,

_nether_, or similar forms, occurs in innumerable ancient writings.

Among such references are Jeremiah (II., 22) Proverbs (XXV., 20),

Herodotus (II., 86, 87), Aristotle (_Prob._ I., 39, _De Mirab._ 54),

Theophrastus (_De Igne_ 435 ed. Heinsii, Hist. Plants III., 9),

Dioscorides (V., 89), Pliny (XIV., 26, and XXXI., 46). A review of

disputations on what salts this term comprised among the Ancients would

itself fill a volume, but from the properties named it was no doubt

mostly soda, more rarely potash, and sometimes both mixed with common

salt. There is every reason to believe from the properties and uses

mentioned, that it did not generally comprise nitre (saltpetre)--into

which superficial error the nomenclature has led many translators. The

preparation by way of burning, and the use of _nitrum_ for purposes for

which we now use soap, for making glass, for medicines, cosmetics,

salves, painting, in baking powder, for preserving food, embalming,

etc., and the descriptions of its taste in "nitrous" waters,--all answer

for soda and potash, but not for saltpetre. It is possible that the

common occurrence of saltpetre as an efflorescence on walls might

naturally lead to its use, but in any event its distinguishing

characteristics are nowhere mentioned. As sal-ammoniac occurred in the

volcanoes in Italy, it also may have been included in the _nitrum_

mentioned. _Nitrum_ was in the main exported from Egypt, but

Theophrastus mentions its production from wood-ash, and Pliny very

rightly states that burned lees of wine (argol) had the nature of

_nitrum_. Many of the ancient writers understood that it was rendered

more caustic by burning, and still more so by treatment with lime.

According to Beckmann (Hist. of Inventions II., p. 488), the form of the

word _natron_ was first introduced into Europe by two travellers in

Egypt, Peter Ballon and Prosper Alpinus, about 1550. The word was

introduced into mineralogy by Linnaeus in 1736. In the first instance

_natron_ was applied to soda and potash in distinction to _nitre_ for

saltpetre, and later _natron_ was applied solely to soda.

It is desirable to mention here two other forms of soda and potash which

are frequently mentioned by Agricola. "Ashes which wool dyers use"

(_cineres quo infectores lanarum utuntur_).--There is no indication in

any of Agricola's works as to whether this was some special wood-ash or

whether it was the calcined residues from wool washing. The "yolk" or

"suint" of wool, originating from the perspiration of the animal, has

long been a source of crude potash. The water, after washing the wool,

is evaporated, and the residue calcined. It contains about 85%

K_{2}CO_{3}, the remainder being sodium and potassium sulphates. Another

reason for assuming that it was not a wood-ash product, is that these

products are separately mentioned. In either event, whether obtained

from wool residues or from lixiviation of wood-ash, it would be an

impure potash. In some methods of wool dyeing, a wash of soda was first

given, so that it is barely possible that this substance was sodium

carbonate.

"Salt made from the ashes of musk ivy" (_sal ex anthyllidis cinere

factus_,--Glossary, _salalkali_). This would be largely potash.

[7] This wondrous illustration of soda-making from Nile water is no

doubt founded upon Pliny (XXXI., 46). "It is made in almost the same

manner as salt, except that sea-water is put into salt pans, whereas in

the nitrous pans it is water of the Nile; these, with the subsidence of

the Nile during the forty days, are impregnated with _nitrum_."

[8] This paragraph displays hopeless ignorance. Borax was known to

Agricola and greatly used in his time; it certainly was not made from

these compounds, but was imported from Central Asia. Sal-ammoniac was

also known in his time, and was used like borax as a soldering agent.

The reaction given by Agricola would yield free ammonia. The following

historical notes on borax and sal-ammoniac may be of service.

BORAX.--The uncertainties of the ancient distinctions in salts involve

borax deeply. The word _Baurach_ occurs in Geber and the other early

Alchemistic writings, but there is nothing to prove that it was modern

borax. There cannot be the slightest doubt, however, that the material

referred to by Agricola as _borax_ was our borax, because of the

characteristic qualities incidentally mentioned in Book VII. That he

believed it was an artificial product from _nitrum_ is evident enough

from his usual expression "_chrysocolla_ made from _nitrum_, which the

Moors call _borax_." Agricola, in _De Natura Fossilium_ (p. 206-7),

makes the following statements, which could leave no doubt on the

subject:--"Native _nitrum_ is found in the earth or on the surface....

It is from this variety that the Venetians make _chrysocolla_, which I

call _borax_.... The second variety of artificial _nitrum_ is made at

the present day from the native _nitrum_, called by the Arabs _tincar_,

but I call it usually by the Greek name _chrysocolla_; it is really the

Arabic _borax_.... This _nitrum_ does not decrepitate nor fly out of the

fire; however, the native variety swells up from within." The

application of the word _chrysocolla_ (_chrysos_, gold; _colla_, solder)

to soldering materials, and at the same time to the copper mineral, is

of Greek origin. If any further proof were needed as to the substance

meant by Agricola, it lies in the word _tincar_. For a long time the

borax of Europe was imported from Central Asia, through Constantinople

and Venice, under the name of _tincal_ or _tincar_. When this trade

began, we do not know; evidently before Agricola's time. The statement

here of making borax from alum and sal-ammoniac is identical with the

assertion of Biringuccio (II., 9).

SAL-AMMONIAC.--The early history of this--ammonium chloride--is also

under a cloud. Pliny (XXXI., 39) speaks of a _sal-hammoniacum_, and

Dioscorides (V., 85) uses much the same word. Pliny describes it as from

near the temple of Ammon in Egypt. None of the distinctive

characteristics of sal-ammoniac are mentioned, and there is every reason

to believe it was either common salt or soda. Herodotus, Strabo, and

others mention common salt sent from about the same locality. The first

authentic mention is in Geber, who calls it _sal-ammoniacum_, and

describes a method of making, and several characteristic reactions. It

was known in the Middle Ages under various names, among them

_sal-aremonicum_. Agricola (_De Nat. Fos._, III., p. 206) notes its

characteristic quality of volatilization. "Sal-ammoniac ... in the fire

neither crackles nor flies out, but is totally consumed." He also says

(p. 208): "Borax is used by goldsmiths to solder gold, likewise silver.

The artificers who make iron needles (tacks?) similarly use sal-ammoniac

when they cover the heads with tin." The statement from Pliny mentioned

in this paragraph is from XXXIII., 29, where he describes the

_chrysocolla_ used as gold solder as made from verdigris, _nitrum_, and

urine in the way quoted. It is quite possible that this solder was

sal-ammoniac, though not made in quite this manner. Pliny refers in

several places (XXXIII., 26, 27, 28, and 29, XXXV., 28, etc.) to

_chrysocolla_, about which he is greatly confused as between

gold-solder, the copper mineral, and a green pigment, the latter being

of either mineral origin.

[9] Saltpetre was secured in the Middle Ages in two ways, but mostly

from the treatment of calcium nitrate efflorescence on cellar and

similar walls, and from so-called saltpetre plantations. In this

description of the latter, one of the most essential factors is omitted

until the last sentence, _i.e._, that the nitrous earth was the result

of the decay of organic or animal matter over a long period. Such

decomposition, in the presence of potassium and calcium carbonates--the

lye and lime--form potassium and calcium nitrates, together with some

magnesium and sodium nitrates. After lixiviation, the addition of lye

converts the calcium and magnesium nitrates into saltpetre, _i.e._,

Ca(NO_{3})_{2} + K_{2}CO_{3} = CaCO_{3} + 2KNO_{3}. The carbonates

precipitate out, leaving the saltpetre in solution, from which it was

evaporated and crystallized out. The addition of alum as mentioned would

scarcely improve the situation.

The purification by repeated re-solution and addition of lye, and

filtration, would eliminate the remaining other salts. The purification

with sulphur, however, is more difficult to understand. In this case the

saltpetre is melted and the sulphur added and set alight. Such an

addition to saltpetre would no doubt burn brilliantly. The potassium

sulphate formed would possibly settle to the bottom, and if the "greasy

matter" were simply organic impurities, they might be burned off. This

method of refining appears to have been copied from Biringuccio (X., 1),

who states it in almost identical terms.

HISTORICAL NOTE.--As mentioned in Note 6 above, it is quite possible

that the Ancients did include efflorescence of walls under _nitrum_;

but, so far as we are aware, no specific mention of such an occurrence

of _nitrum_ is given, and, as stated before, there is every reason to

believe that all the substances under that term were soda and potash.

Especially the frequent mention of the preparation of _nitrum_ by way of

burning, argues strongly against saltpetre being included, as they would

hardly have failed to notice the decrepitation. Argument has been put

forward that Greek fire contained saltpetre, but it amounts to nothing

more than argument, for in those receipts preserved, no salt of any kind

is mentioned. It is most likely that the leprosy of house-walls of the

Mosaic code (Leviticus XIV., 34 to 53) was saltpetre efflorescence. The

drastic treatment by way of destruction of such "unclean" walls and

houses, however, is sufficient evidence that this salt was not used. The

first certain mention of saltpetre (_sal petrae_) is in Geber. As stated

before, the date of this work is uncertain; in any event it was probably

as early as the 13th Century. He describes the making of "solvative

water" with alum and saltpetre, so there can be no doubt as to the

substance (see Note on p. 460, on nitric acid). There is also a work by

a nebulous Marcus Graecus, where the word _sal petrosum_ is used. And it

appears that Roger Bacon (died 1294) and Albertus Magnus (died 1280)

both had access to that work. Bacon uses the term _sal petrae_

frequently enough, and was the first to describe gunpowder (_De Mirabili

Potestate Artis et Naturae_ 1242). He gives no mention of the method of

making his _sal petrae_. Agricola uses throughout the Latin text the

term _halinitrum_, a word he appears to have coined himself. However, he

gives its German equivalent in the _Interpretatio_ as _salpeter_. The

only previous description of the method of making saltpetre, of which we

are aware, is that of Biringuccio (1540), who mentions the boiling of

the excrescences from walls, and also says a good deal about boiling

solutions from "nitrous" earth, which may or may not be of "plantation"

origin. He also gives this same method of refining with sulphur. In any

event, this statement by Agricola is the first clear and complete

description of the saltpetre "plantations." Saltpetre was in great

demand in the Middle Ages for the manufacture of gunpowder, and the

first record of that substance and of explosive weapons necessarily

involves the knowledge of saltpetre. However, authentic mention of such

weapons only begins early in the 14th Century. Among the earliest is an

authority to the Council of Twelve at Florence to appoint persons to

make cannon, etc., (1326), references to cannon in the stores of the

Tower of London, 1388, &c.

[10] There are three methods of manufacturing alum described by

Agricola, the first and third apparently from shales, and the second

from alum rock or "alunite." The reasons for assuming that the first

process was from shales, are the reference to the "aluminous earth" as

ore (_venae_) coming from "veins," and also the mixture of vitriol. In

this process the free sulphuric acid formed by the oxidation of pyrites

reacts upon the argillaceous material to form aluminium sulphate. The

decomposed ore is then placed in tanks and lixiviated. The solution

would contain aluminium sulphate, vitriol, and other impurities. By the

addition of urine, the aluminium sulphate would be converted into

ammonia alum. Agricola is, of course, mistaken as to the effect of the

addition, being under the belief that it separated the vitriol from the

alum; in fact, this belief was general until the latter part of the 18th

Century, when Lavoisier determined that alum must have an alkali base.

Nor is it clear from this description exactly how they were separated.

In a condensed solution allowed to cool, the alum would precipitate out

as "alum meal," and the vitriol would "float on top"--in solution. The

reference to "meal" may represent this phenomenon, and the re-boiling

referred to would be the normal method of purification by

crystallization. The "asbestos" and gypsum deposited in the caldrons

were no doubt feathery and mealy calcium sulphate. The alum produced

would, in any event, be mostly ammonia alum.

The second process is certainly the manufacture from "alum rock" or

"alunite" (the hydrous sulphate of aluminium and potassium), such as

that mined at La Tolfa in the Papal States, where the process has been

for centuries identical with that here described. The alum there

produced is the double basic potassium alum, and crystallizes into cubes

instead of octahedra, _i.e._, the Roman alum of commerce. The presence

of much ferric oxide gives the rose colour referred to by Agricola. This

account is almost identical with that of Biringuccio (II., 4), and it

appears from similarity of details that Agricola, as stated in his

preface, must have "refreshed his mind" from this description; it would

also appear from the preface that he had himself visited the locality.

The third process is essentially the same as the first, except that the

decomposition of the pyrites was hastened by roasting. The following

obscure statement of some interest occurs in Agricola's _De Natura

Fossilium_, p. 209:--"... alum is made from vitriol, for when oil is

made from the latter, alum is distilled out (_expirat_). This absorbs

the clay which is used in cementing glass, and when the operation is

complete the clay is macerated with pure water, and the alum is soon

afterward deposited in the shape of small cubes." Assuming the oil of

vitriol to be sulphuric acid and the clay "used in cementing glass" to

be kaolin, we have here the first suggestion of a method for producing

alum which came into use long after.

"Burnt alum" (_alumen coctum_).--Agricola frequently uses this

expression, and on p. 568, describes the operation, and the substance is

apparently the same as modern dehydrated alum, often referred to as

"burnt alum."

HISTORICAL NOTES.--Whether the Ancients knew of alum in the modern sense

is a most vexed question. The Greeks refer to a certain substance as

_stypteria_, and the Romans refer to this same substance as _alumen_.

There can be no question as to their knowledge and common use of

vitriol, nor that substances which they believed were entirely different

from vitriol were comprised under the above names. Beckmann (Hist. of

Inventions, Vol. I., p. 181) seems to have been the founder of the

doctrine that the ancient _alumen_ was vitriol, and scores of

authorities seem to have adopted his arguments without inquiry, until

that belief is now general. One of the strongest reasons put forward was

that alum does not occur native in appreciable quantities. Apart from

the fact that the weight of this argument has been lost by the discovery

that alum does occur in nature to some extent as an aftermath of

volcanic action, and as an efflorescence from argillaceous rocks, we see

no reason why the Ancients may not have prepared it artificially. One of

the earliest mentions of such a substance is by Herodotus (II., 180) of

a thousand talents of _stypteria_, sent by Amasis from Egypt as a

contribution to the rebuilding of the temple of Delphi. Diodorus (V., 1)

mentions the abundance which was secured from the Lipari Islands

(Stromboli, etc.), and a small quantity from the Isle of Melos.

Dioscorides (V., 82) mentions Egypt, Lipari Islands, Melos, Sardinia,

Armenia, etc., "and generally in any other places where one finds red

ochre (_rubrica_)." Pliny (XXXV., 52) gives these same localities, and

is more explicit as to how it originates--"from an earthy water which

exudes from the earth." Of these localities, the Lipari Islands

(Stromboli, etc.), and Melos are volcanic enough, and both Lipari and

Melos are now known to produce natural alum (Dana. Syst. Min., p. 95;

and Tournefort, "_Relation d'un voyage du Levant_." London, 1717,

_Lettre_ IV., Vol. 1.). Further, the hair-like alum of Dioscorides,

repeated by Pliny below, was quite conceivably fibrous _kalinite_,

native potash alum, which occurs commonly as an efflorescence. Be the

question of native alum as it may--and vitriol is not much more

common--our own view that the ancient _alumen_ was alum, is equally

based upon the artificial product. Before entering upon the subject, we

consider it desirable to set out the properties of the ancient

substance, a complete review of which is given by Pliny (XXXV., 52), he

obviously quoting also from Dioscorides, which, therefore, we do not

need to reproduce. Pliny says:--

"Not less important, or indeed dissimilar, are the uses made of

_alumen_; by which name is understood a sort of salty earth. Of this,

there are several kinds. In Cyprus there is a white _alumen_, and a

darker kind. There is not a great difference in their colour, though the

uses made of them are very dissimilar,--the white _alumen_ being

employed in a liquid state for dyeing wool bright colours, and the

dark-coloured _alumen_, on the other hand, for giving wool a sombre

tint. Gold is purified with black _alumen_. Every kind of _alumen_ is

from a _limus_ water which exudes from the earth. The collection of it

commences in winter, and it is dried by the summer sun. That portion of

it which first matures is the whitest. It is obtained in Spain, Egypt,

Armenia, Macedonia, Pontus, Africa, and the islands of Sardinia, Melos,

Lipari, and Strongyle; the most esteemed, however, is that of Egypt, the

next best from Melos. Of this last there are two kinds, the liquid

_alumen_, and the solid. Liquid _alumen_, to be good, should be of a

limpid and milky appearance; when rubbed, it should be without

roughness, and should give a little heat. This is called _phorimon_. The

mode of detecting whether it has been adulterated is by pomegranate

juice, for, if genuine, the mixture turns black. The other, or solid, is

pale and rough and turns dark with nut-galls; for which reason it is

called _paraphoron_. Liquid _alumen_ is naturally astringent,

indurative, and corrosive; used in combination with honey, it heals

ulcerations.... There is one kind of solid _alumen_, called by the

Greeks _schistos_, which splits into filaments of a whitish colour; for

which reason some prefer calling it _trichitis_ (hair like). _Alumen_ is

produced from the stone _chalcitis_, from which copper is also made,

being a sort of coagulated scum from that stone. This kind of _alumen_

is less astringent than the others, and is less useful as a check upon

bad humours of the body.... The mode of preparing it is to cook it in a

pan until it has ceased being a liquid. There is another variety of

_alumen_ also, of a less active nature, called _strongyle_. It is of two

kinds. The fungous, which easily dissolves, is utterly condemned. The

better kind is the pumice-like kind, full of small holes like a sponge,

and is in round pieces, more nearly white in colour, somewhat greasy,

free from grit, friable, and does not stain black. This last kind is

cooked by itself upon charcoal until it is reduced to pure ashes. The

best kind of all is that called _melinum_, from the Isle of Melos, as I

have said, none being more effectual as an astringent, for staining

black, and for indurating, and none becomes more dry.... Above all other

properties of _alumen_ is its remarkable astringency, whence its Greek

name.... It is injected for dysentry and employed as a gargle." The

lines omitted refer entirely to medical matters which have no bearing

here. The following paragraph (often overlooked) from Pliny (XXXV., 42)

also has an important bearing upon the subject:--"In Egypt they employ a

wonderful method of dyeing. The white cloth, after it is pressed, is

stained in various places, not with dye stuffs, but with substances

which absorb colours. These applications are not apparent on the cloth,

but when it is immersed in a caldron of hot dye it is removed the next

moment brightly coloured. The remarkable circumstance is that although

there be only one dye in the caldron yet different colours appear in the

cloth."

It is obvious from Pliny's description above, and also from the making

of vitriol (see Note 11, p. 572), that this substance was obtained from

liquor resulting from natural or artificial lixiviation of rocks--in the

case of vitriols undoubtedly the result of decomposition of pyritiferous

rocks (such as _chalcitis_). Such liquors are bound to contain aluminum

sulphate if there is any earth or clay about, and whether they contained

alum would be a question of an alkali being present. If no alkali were

present in this liquor, vitriol would crystallize out first, and

subsequent condensation would yield aluminum sulphate. If alkali were

present, the alum would crystallize out either before or with the

vitriol. Pliny's remark, "that portion of it which first matures is

whitest", agrees well enough with this hypothesis. No one will doubt

that some of the properties mentioned above belong peculiarly to

vitriol, but equally convincing are properties and uses that belong to

alum alone. The strongly astringent taste, white colour, and injection

for dysentry, are more peculiar to alum than to vitriol. But above all

other properties is that displayed in dyeing, for certainly if we read

this last quotation from Pliny in conjunction with the statement that

white _alumen_ produces bright colours and the dark kind, sombre

colours, we have the exact reactions of alum and vitriol when used as

mordants. Therefore, our view is that the ancient salt of this character

was a more or less impure mixture ranging from alum to vitriol--"the

whiter the better." Further, considering the ancient knowledge of soda

(_nitrum_), and the habit of mixing it into almost everything, it does

not require much flight of imagination to conceive its admixture to the

"water," and the absolute production of alum.

Whatever may have been the confusion between alum and vitriol among the

Ancients, it appears that by the time of the works attributed to Geber

(12th or 13th Century), the difference was well known. His work

(_Investigationes perfectiones_, IV.) refers to _alumen glaciale_ and

_alumen jameni_ as distinguished from vitriol, and gives characteristic

reactions which can leave no doubt as to the distinction. We may remark

here that the repeated statement apparently arising from Meyer (History

of Chemistry, p. 51) that Geber used the term _alum de rocca_ is untrue,

this term not appearing in the early Latin translations. During the 15th

Century alum did come to be known in Europe as _alum de rocca_. Various

attempts have been made to explain the origin of this term, ranging from

the Italian root, a "rock," to the town of Rocca in Syria, where alum

was supposed to have been produced. In any event, the supply for a long

period prior to the middle of the 15th Century came from Turkey, and the

origin of the methods of manufacture described by Agricola, and used

down to the present day, must have come from the Orient.

In the early part of the 15th Century, a large trade in alum was done

between Italy and Asia Minor, and eventually various Italians

established themselves near Constantinople and Smyrna for its

manufacture (Dudae, _Historia Byzantina Venetia_, 1729, p. 71). The alum

was secured by burning the rock, and lixiviation. With the capture of

Constantinople by the Turks (1453), great feeling grew up in Italy over

the necessity of buying this requisite for their dyeing establishments

from the infidel, and considerable exertion was made to find other

sources of supply. Some minor works were attempted, but nothing much

eventuated until the appearance of one John de Castro. From the

Commentaries of Pope Pius II. (1614, p. 185), it appears that this

Italian had been engaged in dyeing cloth in Constantinople, and thus

became aware of the methods of making alum. Driven out of that city

through its capture by the Turks, he returned to Italy and obtained an

office under the Apostolic Chamber. While in this occupation he

discovered a rock at Tolfa which appeared to him identical with that

used at Constantinople in alum manufacture. After experimental work, he

sought the aid of the Pope, which he obtained after much vicissitude.

Experts were sent, who after examination "shed tears of joy, they

kneeling down three times, worshipped God and praised His kindness in

conferring such a gift on their age." Castro was rewarded, and the great

papal monopoly was gradually built upon this discovery. The industry

firmly established at Tolfa exists to the present day, and is the source

of the Roman alum of commerce. The Pope maintained this monopoly

strenuously, by fair means and by excommunication, gradually advancing

the price until the consumers had greater complaint than against the

Turks. The history of the disputes arising over the papal alum monopoly

would alone fill a volume.

By the middle of the 15th Century alum was being made in Spain, Holland,

and Germany, and later in England. In her efforts to encourage home

industries and escape the tribute to the Pope, Elizabeth (see Note on p.

283) invited over "certain foreign chymistes and mineral masters" and

gave them special grants to induce them to "settle in these realmes."

Among them was Cornelius Devoz, to whom was granted the privilege of

"mining and digging in our Realm of England for allom and copperas."

What Devoz accomplished is not recorded, but the first alum manufacture

on a considerable scale seems to have been in Yorkshire, by one Thomas

Chaloner (about 1608), who was supposed to have seduced workmen from the

Pope's alum works at Tolfa, for which he was duly cursed with all the

weight of the Pope and Church. (Pennant, Tour of Scotland, 1786).

[11] The term for vitriol used by the Roman authors, followed by

Agricola, is _atramentum sutorium_, literally shoemaker's blacking, the

term no doubt arising from its ancient (and modern) use for blackening

leather. The Greek term was _chalcanthon_. The term "vitriol" seems

first to appear in Albertus Magnus (_De Mineralibus_, _Liber_ V.), who

died in 1280, where he uses the expression "_atramentum viride a

quibusdam vitreolum vocatur_." Agricola (_De Nat. Foss._, p. 213)

states, "In recent years the name _vitriolum_ has been given to it." The

first adequate description of vitriol is by Dioscorides (V., 76), as

follows:--"Vitriol (_chalcanthon_) is of one genus, and is a solidified

liquid, but it has three different species. One is formed from the

liquids which trickle down drop by drop and congeal in certain mines;

therefore those who work in the Cyprian mines call it _stalactis_.

Petesius calls this kind _pinarion_. The second kind is that which

collects in certain caverns; afterward it is poured into trenches, where

it congeals, whence it derives its name _pectos_. The third kind is

called _hephthon_ and is mostly made in Spain; it has a beautiful colour

but is weak. The manner of preparing it is as follows: dissolving it in

water, they boil it, and then they transfer it to cisterns and leave it

to settle. After a certain number of days it congeals and separates into

many small pieces, having the form of dice, which stick together like

grapes. The most valued is blue, heavy, dense, and translucent." Pliny

(XXXIV., 32) says:--"By the name which they have given to it, the Greeks

indicate the similar nature of copper and _atramentum sutorium_, for

they call it _chalcanthon_. There is no substance of an equally

miraculous nature. It is made in Spain from wells of this kind of water.

This water is boiled with an equal quantity of pure water, and is then

poured into wooden tanks (fish ponds). Across these tanks there are

fixed beams, to which hang cords stretched by little stones. Upon these

cords adheres the _limus_ (Agricola's 'juice') in drops of a vitreous

appearance, somewhat resembling a bunch of grapes. After removal, it is

dried for thirty days. It is of a blue colour, and of a brilliant

lustre, and is very like glass. Its solution is the blacking used for

colouring leather. _Chalcanthon_ is made in many other ways: its kind of

earth is sometimes dug from ditches, from the sides of which exude

drops, which solidify by the winter frosts into icicles, called

_stalagmia_, and there is none more pure. When its colour is nearly

white, with a slight tinge of violet, it is called _leukoion_. It is

also made in rock basins, the rain water collecting the _limus_ into

them, where it becomes hardened. It is also made in the same way as salt

by the intense heat of the sun. Hence it is that some distinguish two

kinds, the mineral and the artificial; the latter being paler than the

former and as much inferior to it in quality as it is in colour."

While Pliny gives prominence to blue vitriol, his solution for colouring

leather must have been the iron sulphate. There can be no doubt from the

above, however, that both iron and copper sulphates were known to the

Ancients. From the methods for making vitriol given here in _De Re

Metallica_, it is evident that only the iron sulphate would be produced,

for the introduction of iron strips into the vats would effectually

precipitate any copper. It is our belief that generally throughout this

work, the iron sulphate is meant by the term _atramentum sutorium_. In

_De Natura Fossilium_ (p. 213-15) Agricola gives three varieties of

_atramentum sutorium_,--_viride_, _caeruleum_, and _candidum_, _i.e._,

green, blue, and white. Thus the first mention of white vitriol (zinc

sulphate) appears to be due to him, and he states further (p. 213): "A

white sort is found, especially at Goslar, in the shape of icicles,

transparent like crystals." And on p. 215: "Since I have explained the

nature of vitriol and its relatives, which are obtained from cupriferous

pyrites, I will next speak of an acrid solidified juice which commonly

comes from _cadmia_. It is found at Annaberg in the tunnel driven to the

Saint Otto mine; it is hard and white, and so acrid that it kills mice,

crickets, and every kind of animal. However, that feathery substance

which oozes out from the mountain rocks and the thick substance found

hanging in tunnels and caves from which saltpetre is made, while

frequently acrid, does not come from _cadmia_." Dana (Syst. of Min., p.

939) identifies this as _Goslarite_--native zinc sulphate. It does not

appear, however, that artificial zinc vitriol was made in Agricola's

time. Schlueter (_Huette-Werken_, Braunschweig 1738, p. 597) states it to

have been made for the first time at Rammelsberg about 1570.

It is desirable here to enquire into the nature of the substances given

by all of the old mineralogists under the Latinized Greek terms

_chalcitis_, _misy_, _sory_, and _melanteria_. The first mention of

these minerals is in Dioscorides, who (V., 75-77) says: "The best

_chalcitis_ is like copper. It is friable, not stony, and is intersected

by long brilliant veins.... _Misy_ is obtained from Cyprus; it should

have the appearance of gold, be hard, and when pulverised it should have

the colour of gold and sparkle like stars. It has the same properties as

_chalcitis_.... The best is from Egypt.... One kind of _melanteria_

congeals like salt in the entries to copper mines. The other kind is

earthy and appears on the surface of the aforesaid mines. It is found in

the mines of Cilicia and other regions. The best has the colour of

sulphur, is smooth, pure, homogenous, and upon contact with water

immediately becomes black.... Those who consider _sory_ to be the same

as _melanteria_, err greatly. _Sory_ is a species of its own, though it

is not dissimilar. The smell of _sory_ is oppressive and provokes

nausea. It is found in Egypt and in other regions, as Libya, Spain, and

Cyprus. The best is from Egypt, and when broken is black, porous,

greasy, and astringent." Pliny (XXXIV., 29-31) says:--"That is called

_chalcitis_ from which, as well as itself copper (?) is extracted by

heat. It differs from _cadmia_ in that this is obtained from rocks near

the surface, while that is taken from rocks below the surface. Also

_chalcitis_ is immediately friable, being naturally so soft as to appear

like compressed wool. There is also this other distinction; _chalcitis_

contains three other substances, copper, _misy_, and _sory_. Of each of

these we shall speak in their appropriate places. It contains elongated

copper veins. The most approved kind is of the colour of honey; it is

streaked with fine sinuous veins and is friable and not stony. It is

considered most valuable when fresh.... The _sory_ of Egypt is the most

esteemed, being much superior to that of Cyprus, Spain, and Africa;

although some prefer the _sory_ from Cyprus for affections of the eyes.

But from whatever nation it comes, the best is that which has the

strongest odour, and which, when ground up, becomes greasy, black, and

spongy. It is a substance so unpleasant to the stomach that some persons

are nauseated by its smell. Some say that _misy_ is made by the burning

of stones in trenches, its fine yellow powder being mixed with the ashes

of pine-wood. The truth is, as I said above, that though obtained from

the stone, it is already made and in solid masses, which require force

to detach them. The best comes from the works of Cyprus, its

characteristics being that when broken it sparkles like gold, and when

ground it presents a sandy appearance, but on the contrary, if heated,

it is similar to _chalcitis_. _Misy_ is used in refining gold...."

Agricola's views on the subject appear in _De Natura Fossilium_. He says

(p. 212):--"The cupriferous pyrites (_pyrites aerosus_) called

_chalcitis_ is the mother and cause of _sory_--which is likewise known

as mine _vitriol_ (_atramentum metallicum_)--and _melanteria_. These in

turn yield vitriol and such related things. This may be seen especially

at Goslar, where the nodular lumps of dark grey colour are called

vitriol stone (_lapis atramenti_). In the centre of them is found

greyish pyrites, almost dissolved, the size of a walnut. It is enclosed

on all sides, sometimes by _sory_, sometimes by _melanteria_. From them

start little veinlets of greenish vitriol which spread all over it,

presenting somewhat the appearance of hairs extending in all directions

and cohering together.... There are five species of this solidified

juice, _melanteria_, _sory_, _chalcitis_, _misy_, and vitriol. Sometimes

many are found in one place, sometimes all of them, for one originates

from the other. From pyrites, which is, as one might say, the root of

all these juices, originates the above-mentioned _sory_ and

_melanteria_. From _sory_, _chalcitis_, and _melanteria_ originate the

various kinds of vitriol.... _Sory_, _melanteria_, _chalcitis_, and

_misy_ are always native; vitriol alone is either native or artificial.

From them vitriol effloresces white, and sometimes green or blue. _Misy_

effloresces not only from _sory_, _melanteria_, and _chalcitis_, but

also from all the vitriols, artificial as well as natural.... _Sory_ and

_melanteria_ differ somewhat from the others, but they are of the same

colours, grey and black; but _chalcitis_ is red and copper-coloured;

_misy_ is yellow or gold-coloured. All these native varieties have the

odour of lightning (brimstone), but _sory_ is the most powerful. The

feathery vitriol is soft and fine and hair-like, and _melanteria_ has

the appearance of wool and it has a similarity to salt; all these are

rare and light; _sory_, _chalcitis_, and _misy_ have the following

relations. _Sory_ because of its density has the hardness of stone,

although its texture is very coarse. _Misy_ has a very fine texture.

_Chalcitis_ is between the two; because of its roughness and strong

odour it differs from _melanteria_, although they do not differ in

colour. The vitriols, whether natural or artificial, are hard and dense

... as regarding shape, _sory_, _chalcitis_, _misy_, and _melanteria_

are nodular, but _sory_ is occasionally porous, which is peculiar to it.

_Misy_ when it effloresces in no great quantity from the others is like

a kind of pollen, otherwise it is nodular. _Melanteria_ sometimes

resembles wool, sometimes salt."

The sum and substance, therefore, appears to be that _misy_ is a

yellowish material, possibly ochre, and _sory_ a blackish stone, both

impregnated with vitriol. _Chalcitis_ is a partially decomposed pyrites;

and _melanteria_ is no doubt native vitriol. From this last term comes

the modern _melanterite_, native hydrous ferrous sulphate. Dana (System

of Mineralogy, p. 964) considers _misy_ to be in part _copiapite_--basic

ferric sulphate--but any such part would not come under Agricola's

objection to it as a source of vitriol. The disabilities of this and

_chalcitis_ may, however, be due to their copper content.

[12] Agricola (_De Nat. Fos._, 221) says:--"There is a species of

artificial sulphur made from sulphur and iron hammer-scales, melted

together and poured into moulds. This, because it heals scabs of horses,

is generally called _caballinum_." It is difficult to believe such a

combination was other than iron sulphide, but it is equally difficult to

understand how it was serviceable for this purpose.

[13] Inasmuch as pyrites is discussed in the next paragraph, the

material of the first distillation appears to be native sulphur. Until

the receiving pots became heated above the melting point of the sulphur,

the product would be "flowers of sulphur," and not the wax-like product.

The equipment described for pyrites in the next paragraph would be

obviously useful only for coarse material.

But little can be said on the history of sulphur; it is mentioned often

enough in the Bible and also by Homer (Od. XXII., 481). The Greeks

apparently knew how to refine it, although neither Dioscorides nor Pliny

specifically describes such an operation. Agricola says (_De Nat. Fos._,

220): "Sulphur is of two kinds; the mineral, which the Latins call

_vivum_, and the Greeks _apyron_, which means 'not exposed to the fire'

(_ignem non expertum_) as rightly interpreted by Celsius; and the

artificial, called by the Greeks _pepyromenon_, that is, 'exposed to the

fire.'" In Book X., the expression _sulfur ignem non expertum_

frequently appears, no doubt in Agricola's mind for native sulphur,

although it is quite possible that the Greek distinction was between

"flowers" of sulphur and the "wax-like" variety.

[14] The substances referred to under the names _bitumen_, _asphalt_,

_maltha_, _naphtha_, _petroleum_, _rock-oil_, etc., have been known and

used from most ancient times, and much of our modern nomenclature is of

actual Greek and Roman ancestry. These peoples distinguished three

related substances,--the Greek _asphaltos_ and Roman _bitumen_ for the

hard material,--Greek _pissasphaltos_ and Roman _maltha_ for the

viscous, pitchy variety--and occasionally the Greek _naphtha_ and Roman

_naphtha_ for petroleum proper, although it is often enough referred to

as liquid _bitumen_ or liquid _asphaltos_. The term _petroleum_

apparently first appears in Agricola's _De Natura Fossilium_ (p. 222),

where he says the "oil of bitumen ... now called _petroleum_." Bitumen

was used by the Egyptians for embalming from pre-historic times, _i.e._,

prior to 5000 B.C., the term "mummy" arising from the Persian word for

bitumen, _mumiai_. It is mentioned in the tribute from Babylonia to

Thotmes III., who lived about 1500 B.C. (Wilkinson, Ancient Egyptians

I., p. 397). The Egyptians, however, did not need to go further afield

than the Sinai Peninsula for abundant supplies. Bitumen is often cited

as the real meaning of the "slime" mentioned in Genesis (XI., 3; XIV.,

10), and used in building the Tower of Babel. There is no particular

reason for this assumption, except the general association of Babel,

Babylon, and Bitumen. However, the Hebrew word _sift_ for pitch or

bitumen does occur as the cement used for Moses's bulrush cradle (Exodus

II., 3), and Moses is generally accounted about 1300 B.C. Other attempts

to connect Biblical reference to petroleum and bitumen revolve around

Job XXIX., 6, Deut. XXXII., 13, Maccabees II., I, 18, Matthew V., 13,

but all require an unnecessary strain on the imagination.

The plentiful occurrence of bitumen throughout Asia Minor, and

particularly in the Valley of the Euphrates and in Persia, is the

subject of innumerable references by writers from Herodotus (484-424

B.C.) down to the author of the company prospectus of recent months.

Herodotus (I., 179) and Diodorus Siculus (I) state that the walls of

Babylon were mortared with bitumen--a fact partially corroborated by

modern investigation. The following statement by Herodotus (VI., 119) is

probably the source from which Pliny drew the information which Agricola

quotes above. In referring to a well at Ardericca, a place about 40

miles from ancient Susa, in Persia, Herodotus says:--"For from the well

they get bitumen, salt, and oil, procuring it in the way that I will now

describe: they draw with a swipe, and instead of a bucket they make use

of the half of a wine-skin; with this the man dips and, after drawing,

pours the liquid into a reservoir, wherefrom it passes into another, and

there takes three different shapes. The salt and bitumen forthwith

collect and harden, while the oil is drawn off into casks. It is called

by the Persians _rhadinace_, is black, and has an unpleasant smell."

(Rawlinson's Trans. III., p. 409). The statement from Pliny (XXXI., 39)

here referred to by Agricola, reads:--"It (salt) is made from water of

wells poured into salt-pans. At Babylon the first condensed is a

bituminous liquid like oil which is burned in lamps. When this is taken

off, salt is found beneath. In Cappadocia also the water from both wells

and springs is poured into salt-pans." When petroleum began to be used

as an illuminant it is impossible to say. A passage in Aristotle's _De

Mirabilibus_ (127) is often quoted, but in reality it refers only to a

burning spring, a phenomenon noted by many writers, but from which to

its practical use is not a great step. The first really definite

statement as to the use of petroleum as an illuminant is Strabo's

quotation (XVI., 1, 15) from Posidonius: "Asphaltus is found in great

abundance in Babylonia. Eratosthenes describes it as follows:--The

liquid _asphaltus_, which is called _naphtha_, is found in Susa; the dry

kind, which can be made solid, in Babylonia. There is a spring of it

near the Euphrates.... Others say that the liquid kind is also found in

Babylonia.... The liquid kind, called _naphtha_, is of a singular

nature. When it is brought near the fire, the fire catches it....

Posidonius says that there are springs of _naphtha_ in Babylonia, some

of which produce white, others black _naphtha_; the first of these, I

mean white _naphtha_, which attracts flame, is liquid sulphur; the

second or black _naphtha_ is liquid _asphaltus_, and is burnt in lamps

instead of oil." (Hamilton's Translation, Vol. III., p. 151).

Eratosthenes lived about 200 B.C., and Posidonius about 100 years later.

Dioscorides (I., 83), after discussing the usual sources of bitumen

says: "It is found in a liquid state in Agrigentum in Sicily, flowing on

streams; they use it for lights in lanterns in place of oil. Those who

call the Sicilian kind oil are under a delusion, for it is agreed that

it is a kind of liquid bitumen." Pliny adds nothing much new to the

above quotations, except in regard to these same springs (XXXV., 51)

that "The inhabitants collect it on the panicles of reeds, to which it

quickly adheres and they use it for burning in lamps instead of oil."

Agricola (_De Natura Fossilium_, Book IV.) classifies petroleum, coal,

jet, and obsidian, camphor, and amber as varieties of bitumen, and

devotes much space to the refutation of the claims that the last two are

of vegetable origin.

[15] Agricola (_De Natura Fossilium_, p. 215) in discussing substances

which originate from copper, gives among them green _chrysocolla_ (as

distinguished from borax, etc., see Note 8 above), and says: "Native

_chrysocolla_ originates in veins and veinlets, and is found mostly by

itself like sand, or adhering to metallic substances, and when scraped

off from this appears similar to its own sand. Occasionally it is so

thin that very little can be scraped off. Or else it occurs in waters

which, as I have said, wash these minerals, and afterward it settles as

a powder. At Neusohl in the Carpathians, green water flowing from an

ancient tunnel wears away this _chrysocolla_ with it. The water is

collected in thirty large reservoirs, where it deposits the

_chrysocolla_ as a sediment, which they collect every year and

sell,"--as a pigment. This description of its occurrence would apply

equally well to modern _chrysocolla_ or to malachite. The solution from

copper ores would deposit some sort of green incrustation, of carbonates

mostly.

[16] The statement in Pliny (XXXVI., 66) to which Agricola refers is as

follows: "Then as ingenuity was not content with the mixing of _nitrum_,

they began the addition of _lapis magnes_, because of the belief that it

attracts liquefied glass as well as iron. In a similar manner many kinds

of brilliant stones began to be added to the melting, and then shells

and fossil sand. Authors tell us that the glass of India is made of

broken crystal, and in consequence nothing can compare with it. Light

and dry wood is used for fusing, _cyprium_ (copper?) and _nitrum_ being

added, particularly _nitrum_ from Ophir etc."

A great deal of discussion has arisen over this passage, in connection

with what this _lapis magnes_ really was. Pliny (XXXVI., 25) describes

the lodestone under this term, but also says: "There (in Ethiopia) also

is _haematites magnes_, a stone of blood colour, which shows a red

colour if crushed, or of saffron. The _haematites_ has not the same

property of attracting iron as _magnes_." Relying upon this sentence for

an exception to the ordinary sort of _magnes_, and upon the impossible

chemical reaction involved, most commentators have endeavoured to show

that lodestone was not the substance meant by Pliny, but manganese, and

thus they find here the first knowledge of this mineral. There can be

little doubt that Pliny assumed it to be the lodestone, and Agricola

also. Whether the latter had any independent knowledge on this point in

glass-making or was merely quoting Pliny--which seems probable--we do

not know. In any event, Biringuccio, whose work preceded _De Re

Metallica_ by fifteen years, does definitely mention manganese in this

connection. He dismisses this statement of Pliny with the remark (p.

37-38): "The Ancients wrote about lodestones, as Pliny states, and they

mixed it together with _nitrum_ in their first efforts to make glass."

The following passage from this author (p. 36-37), however, is not only

of interest in this connection, but also as possibly being the first

specific mention of manganese under its own name. Moreover, it has been

generally overlooked in the many discussions of the subject. "Of a

similar nature (to _zaffir_) is also another mineral called _manganese_,

which is found, besides in Germany, at the mountain of Viterbo in

Tuscany ... it is the colour of _ferrigno scuro_ (iron slag?). In

melting it one cannot obtain any metal ... but it gives a very fine

colour to glass, so that the glass workers use it in their pigments to

secure an azure colour.... It also has such a property that when put

into melted glass it cleanses it and makes it white, even if it were

green or yellow. In a hot fire it goes off in a vapour like lead, and

turns into ashes."

To enter competently into the discussion of the early history of

glass-making would employ more space than can be given, and would lead

but to a sterile end. It is certain that the art was pre-Grecian, and

that the Egyptians were possessed of some knowledge of making and

blowing it in the XI Dynasty (according to Petrie 3,500 B.C.), the wall

painting at Beni Hassen, which represents glass-blowing, being

attributed to that period. The remains of a glass factory at Tel el

Amarna are believed to be of the XVIII Dynasty. (Petrie, 1,500 B.C.).

The art reached a very high state of development among the Greeks and

Romans. No discussion of this subject omits Pliny's well-known story

(XXXVI, 65), which we also add: "The tradition is that a merchant ship

laden with _nitrum_ being moored at this place, the merchants were

preparing their meal on the beach, and not having stones to prop up

their pots, they used lumps of _nitrum_ from the ship, which fused and

mixed with the sands of the shore, and there flowed streams of a new

translucent liquid, and thus was the origin of glass."

APPENDIX A.

AGRICOLA'S WORKS.

Georgius Agricola was not only the author of works on Mining and allied

subjects, usually associated with his name, but he also interested

himself to some extent in political and religious subjects. For

convenience in discussion we may, therefore, divide his writings on the

broad lines of (1) works on mining, geology, mineralogy, and allied

subjects; (2) works on other subjects, medical, religious, critical,

political, and historical. In respect especially to the first division,

and partially with regard to the others, we find three principal cases:

(_a_) Works which can be authenticated in European libraries to-day;

(_b_) references to editions of these in bibliographies, catalogues,

etc., which we have been unable to authenticate; and (_c_) references to

works either unpublished or lost. The following are the short titles of

all of the published works which we have been able to find on the

subjects allied to mining, arranged according to their present

importance:--_De Re Metallica_, first edition, 1556; _De Natura

Fossilium_, first edition, 1546; _De Ortu et Causis Subterraneorum_,

first edition, 1546; _Bermannus_, first edition, 1530; _Rerum

Metallicarum Interpretatio_, first edition, 1546; _De Mensuris et

Ponderibus_, first edition, 1533; _De Precio Metallorum et Monetis_,

first edition, 1550; _De Veteribus et Novis Metallis_, first edition,

1546; _De Natura eorum quae Effluunt ex Terra_, first edition, 1546; _De

Animantibus Subterraneis_, first edition, 1549.

Of the "lost" or unpublished works, on which there is some evidence, the

following are the most important:--_De Metallicis et Machinis_, _De Ortu

Metallorum Defensio ad Jacobum Scheckium_, _De Jure et Legibus

Metallicis_, _De Varia Temperie sive Constitutione Aeris_, _De Terrae

Motu_, and _Commentariorum, Libri VI_.

The known published works upon other subjects are as follows:--Latin

Grammar, first edition, 1520; Two Religious Tracts, first edition, 1522;

_Galen_ (Joint Revision of Greek Text), first edition, 1525; _De Bello

adversus Turcam_, first edition, 1528; _De Peste_, first edition, 1554.

The lost or partially completed works on subjects unrelated to mining,

of which some trace has been found, are:--_De Medicatis Fontibus_, _De

Putredine solidas partes_, etc., _Castigationes in Hippocratem_,

_Typographia Mysnae et Toringiae_, _De Traditionibus Apostolicis_,

_Oratio de rebus gestis Ernesti et Alberti_, _Ducum Saxoniae_.

REVIEW OF PRINCIPAL WORKS.

Before proceeding with the bibliographical detail, we consider it

desirable to review briefly the most important of the author's works on

subjects related to mining.

_De Natura Fossilium._ This is the most important work of Agricola,

excepting _De Re Metallica_. It has always been printed in combination

with other works, and first appeared at Basel, 1546. This edition was

considerably revised by the author, the amended edition being that of

1558, which we have used in giving references. The work comprises ten

"books" of a total of 217 folio pages. It is the first attempt at

systematic mineralogy, the minerals[1] being classified into (1)

"earths" (clay, ochre, etc.), (2) "stones properly so-called" (gems,

semi-precious and unusual stones, as distinguished from rocks), (3)

"solidified juices" (salt, vitriol, alum, etc.), (4) metals, and (5)

"compounds" (homogeneous "mixtures" of simple substances, thus forming

such minerals as galena, pyrite, etc.). In this classification Agricola

endeavoured to find some fundamental basis, and therefore adopted

solubility, fusibility, odour, taste, etc., but any true classification

without the atomic theory was, of course, impossible. However, he makes

a very creditable performance out of their properties and obvious

characteristics. All of the external characteristics which we use to-day

in discrimination, such as colour, hardness, lustre, etc., are

enumerated, the origin of these being attributed to the proportions of

the Peripatetic elements and their binary properties. Dana, in his great

work[2], among some fourscore minerals which he identifies as having

been described by Agricola and his predecessors, accredits a score to

Agricola himself. It is our belief, however, that although in a few

cases Agricola has been wrongly credited, there are still more of which

priority in description might be assigned to him. While a greater number

than fourscore of so-called species are given by Agricola and his

predecessors, many of these are, in our modern system, but varieties;

for instance, some eight or ten of the ancient species consist of one

form or another of silica.

Book I. is devoted to mineral characteristics--colour, brilliance,

taste, shape, hardness, etc., and to the classification of minerals;

Book II., "earths"--clay, Lemnian earth, chalk, ochre, etc.; Book III.,

"solidified juices"--salt, _nitrum_ (soda and potash), saltpetre, alum,

vitriol, chrysocolla, _caeruleum_ (part azurite), orpiment, realgar, and

sulphur; Book IV., camphor, bitumen, coal, bituminous shales, amber;

Book V., lodestone, bloodstone, gypsum, talc, asbestos, mica, calamine,

various fossils, geodes, emery, touchstones, pumice, fluorspar, and

quartz; Book VI., gems and precious stones; Book VII., "rocks"--marble,

serpentine, onyx, alabaster, limestone, etc.; Book VIII., metals--gold,

silver, quicksilver, copper, lead, tin, antimony, bismuth, iron, and

alloys, such as electrum, brass, etc.; Book IX., various furnace

operations, such as making brass, gilding, tinning, and products such as

slags, furnace accretions, _pompholyx_ (zinc oxide), copper flowers,

litharge, hearth-lead, verdigris, white-lead, red-lead, etc.; Book X.,

"compounds," embracing the description of a number of recognisable

silver, copper, lead, quicksilver, iron, tin, antimony, and zinc

minerals, many of which we set out more fully in Note 8, page 108.