The iron assay furnace is made of four iron bars a foot and a half high;

which at the bottom are bent outward and broadened a short distance to

enable them to stand more firmly; the front part of the furnace is made

from two of these bars, and the back part from two of them; to these

bars on both sides are joined and welded three iron cross-bars, the

first at a height of a palm from the bottom, the second at a height of a

foot, and the third at the top. The upright bars are perforated at that

point where the side cross-bars are joined to them, in order that three

similar iron bars on the remaining sides can be engaged in them; thus

there are twelve cross-bars, which make three stages at unequal

intervals. At the lower stage, the upright bars are distant from each

other one foot and five digits; and at the middle stage the front is

distant from the back three palms and one digit, and the sides are

distant from each other three palms and as many digits; at the highest

stage from the front to the back there is a distance of two palms, and

between the sides three palms, so that in this way the furnace becomes

narrower at the top. Furthermore, an iron rod, bent to the shape of the

mouth, is set into the lowest bar of the front; this mouth, just like

that of the brick furnace, is a palm high and five digits wide. Then the

front cross-bar of the lower stage is perforated on each side of the

mouth, and likewise the back one; through these perforations there pass

two iron rods, thus making altogether four bars in the lower stage, and

these support an iron plate smeared with lute; part of this plate also

projects outside the furnace. The outside of the furnace from the lower

stage to the upper, is covered with iron plates, which are bound to the

bars by iron wires, and smeared with lute to enable them to bear the

heat of the fire as long as possible.

As for the clay furnace, it must be made of fat, thick clay, medium so

far as relates to its softness or hardness. This furnace has exactly the

same height as the iron one, and its base is made of two earthenware

tiles, one foot and three palms long and one foot and one palm wide.

Each side of the fore part of both tiles is gradually cut away for the

length of a palm, so that they are half a foot and a digit wide, which

part projects from the furnace; the tiles are about a digit and a half

thick. The walls are similarly of clay, and are set on the lower tiles

at a distance of a digit from the edge, and support the upper tiles; the

walls are three digits high and have four openings, each of which is

about three digits high; those of the back part and of each side are

five digits wide, and of the front, a palm and a half wide, to enable

the freshly made cupels to be conveniently placed on the hearth, when it

has been thoroughly warmed, that they may be dried there. Both tiles are

bound on the outer edge with iron wire, pressed into them, so that they

will be less easily broken; and the tiles, not unlike the iron

bed-plate, have three openings three digits long and a digit wide, in

order that when the upper one on account of the heat of the fire or for

some other reason has become damaged, the lower one may be exchanged and

take its place. Through these holes, the ashes from the burning

charcoal, as I have stated, fall down, and air blows into the furnace

after passing through the openings in the walls of the chamber. The

furnace is rectangular, and inside at the lower part it is three palms

and one digit wide and three palms and as many digits long. At the upper

part it is two palms and three digits wide, so that it also grows

narrower; it is one foot high; in the middle of the back it is cut out

at the bottom in the shape of a semicircle, of half a digit radius. Not

unlike the furnace before described, it has in its forepart a mouth

which is rounded at the top, one palm high and a palm and a digit wide.

Its door is also made of clay, and this has a window and a handle; even

the lid of the furnace which is made of clay has its own handle,

fastened on with iron wire. The outer parts and sides of this furnace

are bound with iron wires, which are usually pressed in, in the shape of

triangles. The brick furnaces must remain stationary; the clay and iron

ones can be carried from one place to another. Those of brick can be

prepared more quickly, while those of iron are more lasting, and those

of clay are more suitable. Assayers also make temporary furnaces in

another way; they stand three bricks on a hearth, one on each side and a

third one at the back, the forepart lies open to the draught, and on

these bricks is placed an iron plate, upon which they again stand three

bricks, which hold and retain the charcoal.

The setting of one furnace differs from another, in that some are placed

higher and others lower; that one is placed higher, in which the man who

is assaying the ore or metals introduces the scorifier through the mouth

with the tongs; that one is placed lower, into which he introduces the

crucible through its open top.

[Illustration 227 (Crucible Assay Furnace): A--Iron hoop. B--Double

bellows. C--Its nozzle. D--Lever.]

In some cases the assayer uses an iron hoop[4] in place of a furnace;

this is placed upon the hearth of a chimney, the lower edge being daubed

with lute to prevent the blast of the bellows from escaping under it. If

the blast is given slowly, the ore will be smelted and the copper will

melt in the triangular crucible, which is placed in it and taken away

again with the tongs. The hoop is two palms high and half a digit thick;

its diameter is generally one foot and one palm, and where the blast

from the bellows enters into it, it is notched out. The bellows is a

double one, such as goldworkers use, and sometimes smiths. In the middle

of the bellows there is a board in which there is an air-hole, five

digits wide and seven long, covered by a little flap which is fastened

over the air-hole on the lower side of the board; this flap is of equal

length and width. The bellows, without its head, is three feet long, and

at the back is one foot and one palm wide and somewhat rounded, and it

is three palms wide at the head; the head itself is three palms long and

two palms and a digit wide at the part where it joins the boards, then

it gradually becomes narrower. The nozzle, of which there is only one,

is one foot and two digits long; this nozzle, and one-half of the head

in which the nozzle is fixed, are placed in an opening of the wall, this

being one foot and one palm thick; it reaches only to the iron hoop on

the hearth, for it does not project beyond the wall. The hide of the

bellows is fixed to the bellows-boards with its own peculiar kind of

iron nails. It joins both bellows-boards to the head, and over it there

are cross strips of hide fixed to the bellows-boards with broad-headed

nails, and similarly fixed to the head. The middle board of the bellows

rests on an iron bar, to which it is fastened with iron nails clinched

on both ends, so that it cannot move; the iron bar is fixed between two

upright posts, through which it penetrates. Higher up on these upright

posts there is a wooden axle, with iron journals which revolve in the

holes in the posts. In the middle of this axle there is mortised a

lever, fixed with iron nails to prevent it from flying out; the lever is

five and a half feet long, and its posterior end is engaged in the iron

ring of an iron rod which reaches to the "tail" of the lowest

bellows-board, and there engages another similar ring. And so when the

workman pulls down the lever, the lower part of the bellows is raised

and drives the wind into the nozzle; then the wind, penetrating through

the hole in the middle bellows-board, which is called the air-hole,

lifts up the upper part of the bellows, upon whose upper board is a

piece of lead, heavy enough to press down that part of the bellows

again, and this being pressed down blows a blast through the nozzle.

This is the principle of the double bellows, which is peculiar to the

iron hoop where are placed the triangular crucibles in which copper ore

is smelted and copper is melted.

[Illustration 228 (Muffles): A--Broad little windows of muffle.

B--Narrow ones. C--Openings in the back thereof.]

I have spoken of the furnaces and the iron hoop; I will now speak of the

muffles and the crucibles. The muffle is made of clay, in the shape of

an inverted gutter tile; it covers the scorifiers, lest coal dust fall

into them and interfere with the assay. It is a palm and a half broad,

and the height, which corresponds with the mouth of the furnace, is

generally a palm, and it is nearly as long as the furnace; only at the

front end does it touch the mouth of the furnace, everywhere else on the

sides and at the back there is a space of three digits, to allow the

charcoal to lie in the open space between it and the furnace. The muffle

is as thick as a fairly thick earthen jar; its upper part is entire; the

back has two little windows, and each side has two or three or even

four, through which the heat passes into the scorifiers and melts the

ore. In place of little windows, some muffles have small holes, ten in

the back and more on each side. Moreover, in the back below the little

windows, or small holes, there are cut away three semi-circular notches

half a digit high, and on each side there are four. The back of the

muffle is generally a little lower than the front.

[Illustration 229 (Containers): A--Scorifier. B--Triangular crucible.

C--Cupel.]

The crucibles differ in the materials from which they are made, because

they are made of either clay or ashes; and those of clay, which we also

call "earthen," differ in shape and size. Some are made in the shape of

a moderately thick salver (scorifiers), three digits wide, and of a

capacity of an _uncia_ measure; in these the ore mixed with fluxes is

melted, and they are used by those who assay gold or silver ore. Some

are triangular and much thicker and more capacious, holding five, or

six, or even more _unciae_; in these copper is melted, so that it can be

poured out, expanded, and tested with fire, and in these copper ore is

usually melted.

The cupels are made of ashes; like the preceding scorifiers they are

tray-shaped, and their lower part is very thick but their capacity is

less. In these lead is separated from silver, and by them assays are

concluded. Inasmuch as the assayers themselves make the cupels,

something must be said about the material from which they are made, and

the method of making them. Some make them out of all kinds of ordinary

ashes; these are not good, because ashes of this kind contain a certain

amount of fat, whereby such cupels are easily broken when they are hot.

Others make them likewise out of any kind of ashes which have been

previously leached; of this kind are the ashes into which warm water has

been infused for the purpose of making lye. These ashes, after being

dried in the sun or a furnace, are sifted in a hair sieve; and although

warm water washes away the fat from the ashes, still the cupels which

are made from such ashes are not very good because they often contain

charcoal dust, sand, and pebbles. Some make them in the same way out of

any kind of ashes, but first of all pour water into the ashes and remove

the scum which floats thereon; then, after it has become clear, they

pour away the water, and dry the ashes; they then sift them and make the

cupels from them. These, indeed, are good, but not of the best quality,

because ashes of this kind are also not devoid of small pebbles and

sand. To enable cupels of the best quality to be made, all the

impurities must be removed from the ashes. These impurities are of two

kinds; the one sort light, to which class belong charcoal dust and fatty

material and other things which float in water, the other sort heavy,

such as small stones, fine sand, and any other materials which settle in

the bottom of a vessel. Therefore, first of all, water should be poured

into the ashes and the light impurities removed; then the ashes should

be kneaded with the hands, so that they will become properly mixed with

the water. When the water has become muddy and turbid, it should be

poured into a second vessel. In this way the small stones and fine sand,

or any other heavy substance which may be there, remain in the first

vessel, and should be thrown away. When all the ashes have settled in

this second vessel, which will be shown if the water has become clear

and does not taste of the flavour of lye, the water should be thrown

away, and the ashes which have settled in the vessel should be dried in

the sun or in a furnace. This material is suitable for the cupels,

especially if it is the ash of beech wood or other wood which has a

small annual growth; those ashes made from twigs and limbs of vines,

which have rapid annual growth, are not so good, for the cupels made

from them, since they are not sufficiently dry, frequently crack and

break in the fire and absorb the metals. If ashes of beech or similar

wood are not to be had, the assayer makes little balls of such ashes as

he can get, after they have been cleared of impurities in the manner

before described, and puts them in a baker's or potter's oven to burn,

and from these the cupels are made, because the fire consumes whatever

fat or damp there may be. As to all kinds of ashes, the older they are

the better, for it is necessary that they should have the greatest

possible dryness. For this reason ashes obtained from burned bones,

especially from the bones of the heads of animals, are the most suitable

for cupels, as are also those ashes obtained from the horns of deer and

the spines of fishes. Lastly, some take the ashes which are obtained

from burnt scrapings of leather, when the tanners scrape the hides to

clear them from hair. Some prefer to use compounds, that one being

recommended which has one and a half parts of ashes from the bones of

animals or the spines of fishes, and one part of beech ashes, and half a

part of ashes of burnt hide scrapings. From this mixture good cupels are

made, though far better ones are obtained from equal portions of ashes

of burnt hide scrapings, ashes of the bones of heads of sheep and

calves, and ashes of deer horns. But the best of all are produced from

deer horns alone, burnt to powder; this kind, by reason of its extreme

dryness, absorbs metals least of all. Assayers of our own day, however,

generally make the cupels from beech ashes. These ashes, after being

prepared in the manner just described, are first of all sprinkled with

beer or water, to make them stick together, and are then ground in a

small mortar. They are ground again after being mixed with the ashes

obtained from the skulls of beasts or from the spines of fishes; the

more the ashes are ground the better they are. Some rub bricks and

sprinkle the dust so obtained, after sifting it, into the beech ashes,

for dust of this kind does not allow the hearth-lead to absorb the gold

or silver by eating away the cupels. Others, to guard against the same

thing, moisten the cupels with white of egg after they have been made,

and when they have been dried in the sun, again crush them; especially

if they want to assay in it an ore of copper which contains iron. Some

moisten the ashes again and again with cow's milk, and dry them, and

grind them in a small mortar, and then mould the cupels. In the works in

which silver is separated from copper, they make cupels from two parts

of the ashes of the crucible of the cupellation furnace, for these ashes

are very dry, and from one part of bone-ash. Cupels which have been made

in these ways also need to be placed in the sun or in a furnace;

afterward, in whatever way they have been made, they must be kept a long

time in dry places, for the older they are, the dryer and better they

are.

[Illustration 231 (Cupel Moulds and Pestles): A--Little mould.

B--Inverted mould. C--Pestle. D--Its knob. E--Second pestle.]

Not only potters, but also the assayers themselves, make scorifiers and

triangular crucibles. They make them out of fatty clay, which is dry[5],

and neither hard nor soft. With this clay they mix the dust of old

broken crucibles, or of burnt and worn bricks; then they knead with a

pestle the clay thus mixed with dust, and then dry it. As to these

crucibles, the older they are, the dryer and better they are. The

moulds in which the cupels are moulded are of two kinds, that is, a

smaller size and a larger size. In the smaller ones are made the cupels

in which silver or gold is purged from the lead which has absorbed it;

in the larger ones are made cupels in which silver is separated from

copper and lead. Both moulds are made out of brass and have no bottom,

in order that the cupels can be taken out of them whole. The pestles

also are of two kinds, smaller and larger, each likewise of brass, and

from the lower end of them there projects a round knob, and this alone

is pressed into the mould and makes the hollow part of the cupel. The

part which is next to the knob corresponds to the upper part of the

mould.

So much for these matters. I will now speak of the preparation of the

ore for assaying. It is prepared by roasting, burning, crushing, and

washing. It is necessary to take a fixed weight of ore in order that one

may determine how great a portion of it these preparations consume. The

hard stone containing the metal is burned in order that, when its

hardness has been overcome, it can be crushed and washed; indeed, the

very hardest kind, before it is burned, is sprinkled with vinegar, in

order that it may more rapidly soften in the fire. The soft stone should

be broken with a hammer, crushed in a mortar and reduced to powder; then

it should be washed and then dried again. If earth is mixed with the

mineral, it is washed in a basin, and that which settles is assayed in

the fire after it is dried. All mining products which are washed must

again be dried. But ore which is rich in metal is neither burned nor

crushed nor washed, but is roasted, lest that method of preparation

should lose some of the metal. When the fires have been kindled, this

kind of ore is roasted in an enclosed pot, which is stopped up with

lute. A less valuable ore is even burned on a hearth, being placed upon

the charcoal; for we do not make a great expenditure upon metals, if

they are not worth it. However, I will go into fuller details as to all

these methods of preparing ore, both a little later, and in the

following Book.

For the present, I have decided to explain those things which mining

people usually call fluxes[6] because they are added to ores, not only

for assaying, but also for smelting. Great power is discovered in all

these fluxes, but we do not see the same effects produced in every case;

and some are of a very complicated nature. For when they have been mixed

with the ore and are melted in either the assay or the smelting furnace,

some of them, because they melt easily, to some extent melt the ore;

others, because they either make the ore very hot or penetrate into it,

greatly assist the fire in separating the impurities from the metals,

and they also mix the fused part with the lead, or they partly protect

from the fire the ore whose metal contents would be either consumed in

the fire, or carried up with the fumes and fly out of the furnace; some

fluxes absorb the metals. To the first order belongs lead, whether it be

reduced to little granules or resolved into ash by fire, or red-lead[7],

or ochre made from lead[8], or litharge, or hearth-lead, or galena;

also copper, the same either roasted or in leaves or filings[9]; also

the slags of gold, silver, copper, and lead; also soda[10], its slags,

saltpetre, burned alum, vitriol, _sal tostus_, and melted salt[11];

stones which easily melt in hot furnaces, the sand which is made from

them[12]; soft _tophus_[13], and a certain white schist[14]. But lead,

its ashes, red-lead, ochre, and litharge, are more efficacious for ores

which melt easily; hearth-lead for those which melt with difficulty; and

galena for those which melt with greater difficulty. To the second order

belong iron filings, their slag, _sal artificiosus_, argol, dried lees

of vinegar[15], and the lees of the _aqua_ which separates gold from

silver[16]; these lees and _sal artificiosus_ have the power of

penetrating into ore, the argol to a considerable degree, the lees of

vinegar to a greater degree, but most of all those of the _aqua_ which

separates gold from silver; filings and slags of iron, since they melt

more slowly, have the power of heating the ore. To the third order

belong pyrites, the cakes which are melted from them, soda, its slags,

salt, iron, iron scales, iron filings, iron slags, vitriol, the sand

which is resolved from stones which easily melt in the fire, and

_tophus_; but first of all are pyrites and the cakes which are melted

from it, for they absorb the metals of the ore and guard them from the

fire which consumes them. To the fourth order belong lead and copper,

and their relations. And so with regard to fluxes, it is manifest that

some are natural, others fall in the category of slags, and the rest are

purged from slag. When we assay ores, we can without great expense add

to them a small portion of any sort of flux, but when we smelt them we

cannot add a large portion without great expense. We must, therefore,

consider how great the cost is, to avoid incurring a greater expense on

smelting an ore than the profit we make out of the metals which it

yields.

The colour of the fumes which the ore emits after being placed on a hot

shovel or an iron plate, indicates what flux is needed in addition to

the lead, for the purpose of either assaying or smelting. If the fumes

have a purple tint, it is best of all, and the ore does not generally

require any flux whatever. If the fumes are blue, there should be added

cakes melted out of pyrites or other cupriferous rock; if yellow,

litharge and sulphur should be added; if red, glass-galls[17] and salt;

if green, then cakes melted from cupriferous stones, litharge, and

glass-galls; if the fumes are black, melted salt or iron slag, litharge

and white lime rock. If they are white, sulphur and iron which is eaten

with rust; if they are white with green patches, iron slag and sand

obtained from stones which easily melt; if the middle part of the fumes

are yellow and thick, but the outer parts green, the same sand and iron

slag. The colour of the fumes not only gives us information as to the

proper remedies which should be applied to each ore, but also more or

less indication as to the solidified juices which are mixed with it, and

which give forth such fumes. Generally, blue fumes signify that the ore

contains azure yellow, orpiment; red, realgar; green, chrysocolla;

black, black bitumen; white, tin[18]; white with green patches, the same

mixed with chrysocolla; the middle part yellow and other parts green

show that it contains sulphur. Earth, however, and other things dug up

which contain metals, sometimes emit similarly coloured fumes.

If the ore contains any _stibium_, then iron slag is added to it; if

pyrites, then are added cakes melted from a cupriferous stone and sand

made from stones which easily melt. If the ore contains iron, then

pyrites and sulphur are added; for just as iron slag is the flux for an

ore mixed with sulphur, so on the contrary, to a gold or silver ore

containing iron, from which they are not easily separated, is added

sulphur and sand made from stones which easily melt.

_Sal artificiosus_[19] suitable for use in assaying ore is made in many

ways. By the first method, equal portions of argol, lees of vinegar, and

urine, are all boiled down together till turned into salt. The second

method is from equal portions of the ashes which wool-dyers use, of

lime, of argol purified, and of melted salt; one _libra_ of each of

these ingredients is thrown into twenty _librae_ of urine; then all are

boiled down to one-third and strained, and afterward there is added to

what remains one _libra_ and four _unciae_ of unmelted salt, eight

pounds of lye being at the same time poured into the pots, with litharge

smeared around on the inside, and the whole is boiled till the salt

becomes thoroughly dry. The third method follows. Unmelted salt, and

iron which is eaten with rust, are put into a vessel, and after urine

has been poured in, it is covered with a lid and put in a warm place for

thirty days; then the iron is washed in the urine and taken out, and the

residue is boiled until it is turned into salt. In the fourth method by

which _sal artificiosus_ is prepared, the lye made from equal portions

of lime and the ashes which wool-dyers use, together with equal portions

of salt, soap, white argol, and saltpetre, are boiled until in the end

the mixture evaporates and becomes salt. This salt is mixed with the

concentrates from washing, to melt them.

Saltpetre is prepared in the following manner, in order that it may be

suitable for use in assaying ore. It is placed in a pot which is smeared

on the inside with litharge, and lye made of quicklime is repeatedly

poured over it, and it is heated until the fire consumes it. Wherefore

the saltpetre does not kindle with the fire, since it has absorbed the

lime which preserves it, and thus it is prepared[20].

The following compositions[21] are recommended to smelt all ores which

the heat of fire breaks up or melts only with difficulty. Of these, one

is made from stones of the third order, which easily melt when thrown

into hot furnaces. They are crushed into pure white powder, and with

half an _uncia_ of this powder there are mixed two _unciae_ of yellow

litharge, likewise crushed. This mixture is put into a scorifier large

enough to hold it, and placed under the muffle of a hot furnace; when

the charge flows like water, which occurs after half an hour, it is

taken out of the furnace and poured on to a stone, and when it has

hardened it has the appearance of glass, and this is likewise crushed.

This powder is sprinkled over any metalliferous ore which does not

easily melt when we are assaying it, and it causes the slag to exude.

Others, in place of litharge, substitute lead ash,[22] which is made in

the following way: sulphur is thrown into lead which has been melted in

a crucible, and it soon becomes covered with a sort of scum; when this

is removed, sulphur is again thrown in, and the skin which forms is

again taken off; this is frequently repeated, in fact until all the lead

is turned into powder. There is a powerful flux compound which is made

from one _uncia_ each of prepared saltpetre, melted salt, glass-gall,

and argol, and one-third of an _uncia_ of litharge and a _bes_ of glass

ground to powder; this flux, being added to an equal weight of ore,

liquefies it. A more powerful flux is made by placing together in a pot,

smeared on the inside with litharge, equal portions of white argol,

common salt, and prepared saltpetre, and these are heated until a white

powder is obtained from them, and this is mixed with as much litharge;

one part of this compound is mixed with two parts of the ore which is to

be assayed. A still more powerful flux than this is made out of ashes of

black lead, saltpetre, orpiment, _stibium_, and dried lees of the _aqua_

with which gold workers separate gold from silver. The ashes of lead[23]

are made from one pound of lead and one pound of sulphur; the lead is

flattened out into sheets by pounding with a hammer, and placed

alternately with sulphur in a crucible or pot, and they are heated

together until the fire consumes the sulphur and the lead turns to

ashes. One _libra_ of crushed saltpetre is mixed with one _libra_ of

orpiment similarly ground to powder, and the two are cooked in an iron

pan until they liquefy; they are then poured out, and after cooling are

again ground to powder. A _libra_ of _stibium_ and a _bes_ of the dried

lees (_of what?_) are placed alternately in a crucible and heated to the

point at which they form a button, which is similarly reduced to powder.

A _bes_ of this powder and one _libra_ of the ashes of lead, as well as

a _libra_ of powder made out of the saltpetre and orpiment, are mixed

together and a powder is made from them, one part of which added to two

parts of ore liquefies it and cleanses it of dross. But the most

powerful flux is one which has two _drachmae_ of sulphur and as much

glass-galls, and half an _uncia_ of each of the following,--_stibium_,

salt obtained from boiled urine, melted common salt, prepared saltpetre,

litharge, vitriol, argol, salt obtained from ashes of musk ivy, dried

lees of the _aqua_ by which gold-workers separate gold from silver, alum

reduced by fire to powder, and one _uncia_ of camphor[24] combined with

sulphur and ground into powder. A half or whole portion of this mixture,

as the necessity of the case requires, is mixed with one portion of the

ore and two portions of lead, and put in a scorifier; it is sprinkled

with powder of crushed Venetian glass, and when the mixture has been

heated for an hour and a half or two hours, a button will settle in the

bottom of the scorifier, and from it the lead is soon separated.

There is also a flux which separates sulphur, orpiment and realgar from

metalliferous ore. This flux is composed of equal portions of iron slag,

white _tophus_, and salt. After these juices have been secreted, the

ores themselves are melted, with argol added to them. There is one flux

which preserves _stibium_ from the fire, that the fire may not consume

it, and which preserves the metals from the _stibium_; and this is

composed of equal portions of sulphur, prepared saltpetre, melted salt,

and vitriol, heated together in lye until no odour emanates from the

sulphur, which occurs after a space of three or four hours.[25]

It is also worth while to substitute certain other mixtures. Take two

portions of ore properly prepared, one portion of iron filings, and

likewise one portion of salt, and mix; then put them into a scorifier

and place them in a muffle furnace; when they are reduced by the fire

and run together, a button will settle in the bottom of the scorifier.

Or else take equal portions of ore and of lead ochre, and mix with them

a small quantity of iron filings, and put them into a scorifier, then

scatter iron filings over the mixture. Or else take ore which has been

ground to powder and sprinkle it in a crucible, and then sprinkle over

it an equal quantity of salt that has been three or four times moistened

with urine and dried; then, again and again alternately, powdered ore

and salt; next, after the crucible has been covered with a lid and

sealed, it is placed upon burning charcoal. Or else take one portion of

ore, one portion of minute lead granules, half a portion of Venetian

glass, and the same quantity of glass-galls. Or else take one portion of

ore, one portion of lead granules, half a portion of salt, one-fourth of

a portion of argol, and the same quantity of lees of the _aqua_ which

separates gold from silver. Or else take equal portions of prepared ore

and a powder in which there are equal portions of very minute lead

granules, melted salt, _stibium_ and iron slag. Or else take equal

portions of gold ore, vitriol, argol, and of salt. So much for the

fluxes.

In the assay furnace, when it has been prepared in the way in which I

have described, is first placed a muffle. Then selected pieces of live

charcoals are laid on it, for, from pieces of inferior quality, a great

quantity of ash collects around the muffle and hinders the action of the

fire. Then the scorifiers are placed under the muffle with tongs, and

glowing coals are placed under the fore part of the muffle to warm the

scorifiers more quickly; and when the lead or ore is to be placed in the

scorifiers, they are taken out again with the tongs. When the scorifiers

glow in the heat, first of all the ash or small charcoals, if any have

fallen into them, should be blown away with an iron pipe two feet long

and a digit in diameter; this same thing must be done if ash or small

coal has fallen into the cupels. Next, put in a small ball of lead with

the tongs, and when this lead has begun to be turned into fumes and

consumed, add to it the prepared ore wrapped in paper. It is preferable

that the assayer should wrap it in paper, and in this way put it in the

scorifier, than that he should drop it in with a copper ladle; for when

the scorifiers are small, if he uses a ladle he frequently spills some

part of the ore. When the paper is burnt, he stirs the ore with a small

charcoal held in the tongs, so that the lead may absorb the metal which

is mixed in the ore; when this mixture has taken place, the slag partly

adheres by its circumference to the scorifier and makes a kind of black

ring, and partly floats on the lead in which is mixed the gold or

silver; then the slag must be removed from it.

The lead used must be entirely free from every trace of silver, as is

that which is known as _Villacense_.[26] But if this kind is not

obtainable, the lead must be assayed separately, to determine with

certainty that proportion of silver it contains, so that it may be

deducted from the calculation of the ore, and the result be exact; for

unless such lead be used, the assay will be false and misleading. The

lead balls are made with a pair of iron tongs, about one foot long; its

iron claws are so formed that when pressed together they are egg-shaped;

each claw contains a hollow cup, and when the claws are closed there

extends upward from the cup a passage, so there are two openings, one of

which leads to each hollow cup. And so when the molten lead is poured in

through the openings, it flows down into the hollow cup, and two balls

are formed by one pouring.

In this place I ought not to omit mention of another method of assaying

employed by some assayers. They first of all place prepared ore in the

scorifiers and heat it, and afterward they add the lead. Of this method

I cannot approve, for in this way the ore frequently becomes cemented,

and for this reason it does not stir easily afterward, and is very slow

in mixing with the lead.

[Illustration 240a (Tongs): A--Claws of the tongs. B--Iron, giving form

of an egg. C--Opening.]

If the whole space of the furnace covered by the muffle is not filled

with scorifiers, cupels are put in the empty space, in order that they

may become warmed in the meantime. Sometimes, however, it is filled with

scorifiers, when we are assaying many different ores, or many portions

of one ore at the same time. Although the cupels are usually dried in

one hour, yet smaller ones are done more quickly, and the larger ones

more slowly. Unless the cupels are heated before the metal mixed with

lead is placed in them, they frequently break, and the lead always

sputters and sometimes leaps out of them; if the cupel is broken or the

lead leaps out of it, it is necessary to assay another portion of ore;

but if the lead only sputters, then the cupels should be covered with

broad thin pieces of glowing charcoal, and when the lead strikes these,

it falls back again, and thus the mixture is slowly exhaled. Further, if

in the cupellation the lead which is in the mixture is not consumed, but

remains fixed and set, and is covered by a kind of skin, this is a sign

that it has not been heated by a sufficiently hot fire; put into the

mixture, therefore, a dry pine stick, or a twig of a similar tree, and

hold it in the hand in order that it can be drawn away when it has been

heated. Then take care that the heat is sufficient and equal; if the

heat has not passed all round the charge, as it should when everything

is done rightly, but causes it to have a lengthened shape, so that it

appears to have a tail, this is a sign that the heat is deficient where

the tail lies. Then in order that the cupel may be equally heated by the

fire, turn it around with a small iron hook, whose handle is likewise

made of iron and is a foot and a half long.

[Illustration 240b (Hook): Small iron hook.]

Next, if the mixture has not enough lead, add as much of it as is

required with the iron tongs, or with the brass ladle to which is

fastened a very long handle. In order that the charge may not be cooled,

warm the lead beforehand. But it is better at first to add as much lead

as is required to the ore which needs melting, rather than afterward

when the melting has been half finished, that the whole quantity may not

vanish in fumes, but part of it remain fast. When the heat of the fire

has nearly consumed the lead, then is the time when the gold and silver

gleam in their varied colours, and when all the lead has been consumed

the gold or silver settles in the cupel. Then as soon as possible remove

the cupel out of the furnace, and take the button out of it while it is

still warm, in order that it does not adhere to the ashes. This

generally happens if the button is already cold when it is taken out. If

the ashes do adhere to it, do not scrape it with a knife, lest some of

it be lost and the assay be erroneous, but squeeze it with the iron

tongs, so that the ashes drop off through the pressure. Finally, it is

of advantage to make two or three assays of the same ore at the same

time, in order that if by chance one is not successful, the second, or

in any event the third, may be certain.

[Illustration 241 (Shield for Muffle Furnace): A--Handle of tablet.

B--Its crack.]

While the assayer is assaying the ore, in order to prevent the great

heat of the fire from injuring his eyes, it will be useful for him

always to have ready a thin wooden tablet, two palms wide, with a handle

by which it may be held, and with a slit down the middle in order that

he may look through it as through a crack, since it is necessary for him

to look frequently within and carefully to consider everything.

Now the lead which has absorbed the silver from a metallic ore is

consumed in the cupel by the heat in the space of three quarters of an

hour. When the assays are completed the muffle is taken out of the

furnace, and the ashes removed with an iron shovel, not only from the

brick and iron furnaces, but also from the earthen one, so that the

furnace need not be removed from its foundation.

From ore placed in the triangular crucible a button is melted out, from

which metal is afterward made. First of all, glowing charcoal is put

into the iron hoop, then is put in the triangular crucible, which

contains the ore together with those things which can liquefy it and

purge it of its dross; then the fire is blown with the double bellows,

and the ore is heated until the button settles in the bottom of the

crucible. We have explained that there are two methods of assaying

ore,--one, by which the lead is mixed with ore in the scorifier and

afterward again separated from it in the cupel; the other, by which it

is first melted in the triangular earthen crucible and afterward mixed

with lead in the scorifier, and later separated from it in the cupel.

Now let us consider which is more suitable for each ore, or, if neither

is suitable, by what other method in one way or another we can assay it.

We justly begin with a gold ore, which we assay by both methods, for if

it is rich and seems not to be strongly resistant to fire, but to

liquefy easily, one _centumpondium_ of it (known to us as the lesser

weights),[27] together with one and a half, or two _unciae_ of lead of

the larger weights, are mixed together and placed in the scorifier, and

the two are heated in the fire until they are well mixed. But since such

an ore sometimes resists melting, add a little salt to it, either _sal

torrefactus_ or _sal artificiosus_, for this will subdue it, and prevent

the alloy from collecting much dross; stir it frequently with an iron

rod, in order that the lead may flow around the gold on every side, and

absorb it and cast out the waste. When this has been done, take out the

alloy and cleanse it of slag; then place it in the cupel and heat it

until it exhales all the lead, and a bead of gold settles in the bottom.

If the gold ore is seen not to be easily melted in the fire, roast it

and extinguish it with brine. Do this again and again, for the more

often you roast it and extinguish it, the more easily the ore can be

crushed fine, and the more quickly does it melt in the fire and give up

whatever dross it possesses. Mix one part of this ore, when it has been

roasted, crushed, and washed, with three parts of some powder compound

which melts ore, and six parts of lead. Put the charge into the

triangular crucible, place it in the iron hoop to which the double

bellows reaches, and heat first in a slow fire, and afterward gradually

in a fiercer fire, till it melts and flows like water. If the ore does

not melt, add to it a little more of these fluxes, mixed with an equal

portion of yellow litharge, and stir it with a hot iron rod until it all

melts. Then take the crucible out of the hoop, shake off the button when

it has cooled, and when it has been cleansed, melt first in the

scorifier and afterward in the cupel. Finally, rub the gold which has

settled in the bottom of the cupel, after it has been taken out and

cooled, on the touchstone, in order to find out what proportion of

silver it contains. Another method is to put a _centumpondium_ (of the

lesser weights) of gold ore into the triangular crucible, and add to it

a _drachma_ (of the larger weights) of glass-galls. If it resists

melting, add half a _drachma_ of roasted argol, and if even then it

resists, add the same quantity of roasted lees of vinegar, or lees of

the _aqua_ which separates gold from silver, and the button will settle

in the bottom of the crucible. Melt this button again in the scorifier

and a third time in the cupel.

We determine in the following way, before it is melted in the muffle

furnace, whether pyrites contains gold in it or not: if, after being

three times roasted and three times quenched in sharp vinegar, it has

not broken nor changed its colour, there is gold in it. The vinegar by

which it is quenched should be mixed with salt that is put in it, and

frequently stirred and dissolved for three days. Nor is pyrites devoid

of gold, when, after being roasted and then rubbed on the touchstone, it

colours the touchstone in the same way that it coloured it when rubbed

in its crude state. Nor is gold lacking in that, whose concentrates from

washing, when heated in the fire, easily melt, giving forth little smell

and remaining bright; such concentrates are heated in the fire in a

hollowed piece of charcoal covered over with another charcoal.

We also assay gold ore without fire, but more often its sand or the

concentrates which have been made by washing, or the dust gathered up by

some other means. A little of it is slightly moistened with water and

heated until it begins to exhale an odour, and then to one portion of

ore are placed two portions of quicksilver[28] in a wooden dish as deep

as a basin. They are mixed together with a little brine, and are then

ground with a wooden pestle for the space of two hours, until the

mixture becomes of the thickness of dough, and the quicksilver can no

longer be distinguished from the concentrates made by the washing, nor

the concentrates from the quicksilver. Warm, or at least tepid, water is

poured into the dish and the material is washed until the water runs out

clear. Afterward cold water is poured into the same dish, and soon the

quicksilver, which has absorbed all the gold, runs together into a

separate place away from the rest of the concentrates made by washing.

The quicksilver is afterward separated from the gold by means of a pot

covered with soft leather, or with canvas made of woven threads of

cotton; the amalgam is poured into the middle of the cloth or leather,

which sags about one hand's breadth; next, the leather is folded over

and tied with a waxed string, and the dish catches the quicksilver which

is squeezed through it. As for the gold which remains in the leather, it

is placed in a scorifier and purified by being placed near glowing

coals. Others do not wash away the dirt with warm water, but with strong

lye and vinegar, for they pour these liquids into the pot, and also

throw into it the quicksilver mixed with the concentrates made by

washing. Then they set the pot in a warm place, and after twenty-four

hours pour out the liquids with the dirt, and separate the quicksilver

from the gold in the manner which I have described. Then they pour urine

into a jar set in the ground, and in the jar place a pot with holes in

the bottom, and in the pot they place the gold; then the lid is put on

and cemented, and it is joined with the jar; they afterward heat it till

the pot glows red. After it has cooled, if there is copper in the gold

they melt it with lead in a cupel, that the copper may be separated from

it; but if there is silver in the gold they separate them by means of

the _aqua_ which has the power of parting these two metals. There are

some who, when they separate gold from quicksilver, do not pour the

amalgam into a leather, but put it into a gourd-shaped earthen vessel,

which they place in the furnace and heat gradually over burning

charcoal; next, with an iron plate, they cover the opening of the

operculum, which exudes vapour, and as soon as it has ceased to exude,

they smear it with lute and heat it for a short time; then they remove

the operculum from the pot, and wipe off the quicksilver which adheres

to it with a hare's foot, and preserve it for future use. By the latter

method, a greater quantity of quicksilver is lost, and by the former

method, a smaller quantity.

If an ore is rich in silver, as is _rudis_ silver[29], frequently silver

glance, or rarely ruby silver, gray silver, black silver, brown silver,

or yellow silver, as soon as it is cleansed and heated, a

_centumpondium_ (of the lesser weights) of it is placed in an _uncia_ of

molten lead in a cupel, and is heated until the lead exhales. But if the

ore is of poor or moderate quality, it must first be dried, then

crushed, and then to a _centumpondium_ (of the lesser weights) an

_uncia_ of lead is added, and it is heated in the scorifier until it

melts. If it is not soon melted by the fire, it should be sprinkled with

a little powder of the first order of fluxes, and if then it does not

melt, more is added little by little until it melts and exudes its slag;

that this result may be reached sooner, the powder which has been

sprinkled over it should be stirred in with an iron rod. When the

scorifier has been taken out of the assay furnace, the alloy should be

poured into a hole in a baked brick; and when it has cooled and been

cleansed of the slag, it should be placed in a cupel and heated until it

exhales all its lead; the weight of silver which remains in the cupel

indicates what proportion of silver is contained in the ore.

We assay copper ore without lead, for if it is melted with it, the

copper usually exhales and is lost. Therefore, a certain weight of such

an ore is first roasted in a hot fire for about six or eight hours;

next, when it has cooled, it is crushed and washed; then the

concentrates made by washing are again roasted, crushed, washed, dried,

and weighed. The portion which it has lost whilst it is being roasted

and washed is taken into account, and these concentrates by washing

represent the cake which will be melted out of the copper ore. Place

three _centumpondia_ (lesser weights) of this, mixed with three

_centumpondia_ (lesser weights) each of copper scales[30], saltpetre,

and Venetian glass, mixed, into the triangular crucible, and place it in

the iron hoop which is set on the hearth in front of the double bellows.

Cover the crucible with charcoal in such a way that nothing may fall

into the ore which is to be melted, and so that it may melt more

quickly. At first blow a gentle blast with the bellows in order that the

ore may be heated gradually in the fire; then blow strongly till it

melts, and the fire consumes that which has been added to it, and the

ore itself exudes whatever slag it possesses. Next, cool the crucible

which has been taken out, and when this is broken you will find the

copper; weigh this, in order to ascertain how great a portion of the ore

the fire has consumed. Some ore is only once roasted, crushed, and

washed; and of this kind of concentrates, three _centumpondia_ (lesser

weights) are taken with one _centumpondium_ each of common salt, argol

and glass-galls. Heat them in the triangular crucible, and when the

mixture has cooled a button of pure copper will be found, if the ore is

rich in this metal. If, however, it is less rich, a stony lump results,

with which the copper is intermixed; this lump is again roasted,

crushed, and, after adding stones which easily melt and saltpetre, it is

again melted in another crucible, and there settles in the bottom of the

crucible a button of pure copper. If you wish to know what proportion of

silver is in this copper button, melt it in a cupel after adding lead.

With regard to this test I will speak later.

Those who wish to know quickly what portion of silver the copper ore

contains, roast the ore, crush and wash it, then mix a little yellow

litharge with one _centumpondium_ (lesser weights) of the concentrates,

and put the mixture into a scorifier, which they place under the muffle

in a hot furnace for the space of half an hour. When the slag exudes, by

reason of the melting force which is in the litharge, they take the

scorifier out; when it has cooled, they cleanse it of slag and again

crush it, and with one _centumpondium_ of it they mix one and a half

_unciae_ of lead granules. They then put it into another scorifier,

which they place under the muffle in a hot furnace, adding to the

mixture a little of the powder of some one of the fluxes which cause ore

to melt; when it has melted they take it out, and after it has cooled,

cleanse it of slag; lastly, they heat it in the cupel till it has

exhaled all of the lead, and only silver remains.

Lead ore may be assayed by this method: crush half an _uncia_ of pure

lead-stone and the same quantity of the _chrysocolla_ which they call

borax, mix them together, place them in a crucible, and put a glowing

coal in the middle of it. As soon as the borax crackles and the

lead-stone melts, which soon occurs, remove the coal from the crucible,

and the lead will settle to the bottom of it; weigh it out, and take

account of that portion of it which the fire has consumed. If you also

wish to know what portion of silver is contained in the lead, melt the

lead in the cupel until all of it exhales.

Another way is to roast the lead ore, of whatsoever quality it be, wash

it, and put into the crucible one _centumpondium_ of the concentrates,

together with three _centumpondia_ of the powdered compound which melts

ore, mixed together, and place it in the iron hoop that it may melt;

when it has cooled, cleanse it of its slag, and complete the test as I

have already said. Another way is to take two _unciae_ of prepared ore,

five _drachmae_ of roasted copper, one _uncia_ of glass, or glass-galls

reduced to powder, a _semi-uncia_ of salt, and mix them. Put the mixture

into the triangular crucible, and heat it over a gentle fire to prevent

it from breaking; when the mixture has melted, blow the fire vigorously

with the bellows; then take the crucible off the live coals and let it

cool in the open air; do not pour water on it, lest the lead button

being acted upon by the excessive cold should become mixed with the

slag, and the assay in this way be erroneous. When the crucible has

cooled, you will find in the bottom of it the lead button. Another way

is to take two _unciae_ of ore, a _semi-uncia_ of litharge, two

_drachmae_ of Venetian glass and a _semi-uncia_ of saltpetre. If there

is difficulty in melting the ore, add to it iron filings, which, since

they increase the heat, easily separate the waste from lead and other

metals. By the last way, lead ore properly prepared is placed in the

crucible, and there is added to it only the sand made from stones which

easily melt, or iron filings, and then the assay is completed as

formerly.

You can assay tin ore by the following method. First roast it, then

crush, and afterward wash it; the concentrates are again roasted,

crushed, and washed. Mix one and a half _centumpondia_ of this with one

_centumpondium_ of the _chrysocolla_ which they call borax; from the

mixture, when it has been moistened with water, make a lump. Afterwards,

perforate a large round piece of charcoal, making this opening a palm

deep, three digits wide on the upper side and narrower on the lower

side; when the charcoal is put in its place the latter should be on the

bottom and the former uppermost. Let it be placed in a crucible, and let

glowing coal be put round it on all sides; when the perforated piece of

coal begins to burn, the lump is placed in the upper part of the

opening, and it is covered with a wide piece of glowing coal, and after

many pieces of coal have been put round it, a hot fire is blown up with

the bellows, until all the tin has run out of the lower opening of the

charcoal into the crucible. Another way is to take a large piece of

charcoal, hollow it out, and smear it with lute, that the ore may not

leap out when white hot. Next, make a small hole through the middle of

it, then fill up the large opening with small charcoal, and put the ore

upon this; put fire in the small hole and blow the fire with the nozzle

of a hand bellows; place the piece of charcoal in a small crucible,

smeared with lute, in which, when the melting is finished, you will find

a button of tin.

In assaying bismuth ore, place pieces of ore in the scorifier, and put

it under the muffle in a hot furnace; as soon as they are heated, they

drip with bismuth, which runs together into a button.

Quicksilver ore is usually tested by mixing one part of broken ore with

three-parts of charcoal dust and a handful of salt. Put the mixture into

a crucible or a pot or a jar, cover it with a lid, seal it with lute,

place it on glowing charcoal, and as soon as a burnt cinnabar colour

shows in it, take out the vessel; for if you continue the heat too long

the mixture exhales the quicksilver with the fumes. The quicksilver

itself, when it has become cool, is found in the bottom of the crucible

or other vessel. Another way is to place broken ore in a gourd-shaped

earthen vessel, put it in the assay furnace, and cover with an operculum

which has a long spout; under the spout, put an ampulla to receive the

quicksilver which distills. Cold water should be poured into the

ampulla, so that the quicksilver which has been heated by the fire may

be continuously cooled and gathered together, for the quicksilver is

borne over by the force of the fire, and flows down through the spout of

the operculum into the ampulla. We also assay quicksilver ore in the

very same way in which we smelt it. This I will explain in its proper

place.

Lastly, we assay iron ore in the forge of a blacksmith. Such ore is

burned, crushed, washed, and dried; a magnet is laid over the

concentrates, and the particles of iron are attracted to it; these are

wiped off with a brush, and are caught in a crucible, the magnet being

continually passed over the concentrates and the particles wiped off, so

long as there remain any particles which the magnet can attract to it.

These particles are heated in the crucible with saltpetre until they

melt, and an iron button is melted out of them. If the magnet easily and

quickly attracts the particles to it, we infer that the ore is rich in

iron; if slowly, that it is poor; if it appears actually to repel the

ore, then it contains little or no iron. This is enough for the assaying

of ores.

I will now speak of the assaying of the metal alloys. This is done both

by coiners and merchants who buy and sell metal, and by miners, but most

of all by the owners and mine masters, and by the owners and masters of

the works in which the metals are smelted, or in which one metal is

parted from another.

First I will describe the way assays are usually made to ascertain what

portion of precious metal is contained in base metal. Gold and silver

are now reckoned as precious metals and all the others as base metals.

Once upon a time the base metals were burned up, in order that the

precious metals should be left pure; the Ancients even discovered by

such burning what portion of gold was contained in silver, and in this

way all the silver was consumed, which was no small loss. However, the

famous mathematician, Archimedes[31], to gratify King Hiero, invented a

method of testing the silver, which was not very rapid, and was more

accurate for testing a large mass than a small one. This I will explain

in my commentaries. The alchemists have shown us a way of separating

silver from gold by which neither of them is lost[32].

Gold which contains silver,[33] or silver which contains gold, is first

rubbed on the touchstone. Then a needle in which there is a similar

amount of gold or silver is rubbed on the same touchstone, and from the

lines which are produced in this way, is perceived what portion of

silver there is in the gold, or what portion of gold there is in the

silver. Next there is added to the silver which is in the gold, enough

silver to make it three times as much as the gold. Then lead is placed

in a cupel and melted; a little later, a small amount of copper is put

in it, in fact, half an _uncia_ of it, or half an _uncia_ and a

_sicilicus_ (of the smaller weights) if the gold or silver does not

contain any copper. The cupel, when the lead and copper are wanting,

attracts the particles of gold and silver, and absorbs them. Finally,

one-third of a _libra_ of the gold, and one _libra_[34] of the silver

must be placed together in the same cupel and melted; for if the gold

and silver were first placed in the cupel and melted, as I have already

said, it absorbs particles of them, and the gold, when separated from

the silver, will not be found pure. These metals are heated until the

lead and the copper are consumed, and again, the same weight of each is

melted in the same manner in another cupel. The buttons are pounded with

a hammer and flattened out, and each little leaf is shaped in the form

of a tube, and each is put into a small glass ampulla. Over these there

is poured one _uncia_ and one _drachma_ (of the large weight) of the

third quality _aqua valens_, which I will describe in the Tenth Book.

This is heated over a slow fire, and small bubbles, resembling pearls in

shape, will be seen to adhere to the tubes. The redder the _aqua_

appears, the better it is judged to be; when the redness has vanished,

small white bubbles are seen to be resting on the tubes, resembling

pearls not only in shape, but also in colour. After a short time the

_aqua_ is poured off and other is poured on; when this has again raised

six or eight small white bubbles, it is poured off and the tubes are

taken out and washed four or five times with spring water; or if they

are heated with the same water, when it is boiling, they will shine more

brilliantly. Then they are placed in a saucer, which is held in the hand

and gradually dried by the gentle heat of the fire; afterward the saucer

is placed over glowing charcoal and covered with a charcoal, and a

moderate blast is blown upon it with the mouth and then a blue flame

will be emitted. In the end the tubes are weighed, and if their weights

prove equal, he who has undertaken this work has not laboured in vain.

Lastly, both are placed in another balance-pan and weighed; of each tube

four grains must not be counted, on account of the silver which remains

in the gold and cannot be separated from it. From the weight of the

tubes we learn the weight both of the gold and of the silver which is in

the button. If some assayer has omitted to add so much silver to the

gold as to make it three times the quantity, but only double, or two and

a half times as much, he will require the stronger quality of _aqua_

which separates gold from silver, such as the fourth quality. Whether

the _aqua_ which he employs for gold and silver is suitable for the

purpose, or whether it is more or less strong than is right, is

recognised by its effect. That of medium strength raises the little

bubbles on the tubes and is found to colour the ampulla and the

operculum a strong red; the weaker one is found to colour them a light

red, and the stronger one to break the tubes. To pure silver in which

there is some portion of gold, nothing should be added when they are

being heated in the cupel prior to their being parted, except a _bes_ of

lead and one-fourth or one-third its amount of copper of the lesser

weights. If the silver contains in itself a certain amount of copper,

let it be weighed, both after it has been melted with the lead, and

after the gold has been parted from it; by the former we learn how much

copper is in it, by the latter how much gold. Base metals are burnt up

even to-day for the purpose of assay, because to lose so little of the

metal is small loss, but from a large mass of base metal, the precious

metal is always extracted, as I will explain in Books X. and XI.

We assay an alloy of copper and silver in the following way. From a few

cakes of copper the assayer cuts out portions, small samples from small

cakes, medium samples from medium cakes, and large samples from large

cakes; the small ones are equal in size to half a hazel nut, the large

ones do not exceed the size of half a chestnut, and those of medium size

come between the two. He cuts out the samples from the middle of the

bottom of each cake. He places the samples in a new, clean, triangular

crucible and fixes to them pieces of paper upon which are written the

weight of the cakes of copper, of whatever size they may be; for

example, he writes, "These samples have been cut from copper which

weighs twenty _centumpondia_." When he wishes to know how much silver

one _centumpondium_ of copper of this kind has in it, first of all he

throws glowing coals into the iron hoop, then adds charcoal to it. When

the fire has become hot, the paper is taken out of the crucible and put

aside, he then sets that crucible on the fire and gradually heats it for

a quarter of an hour until it becomes red hot. Then he stimulates the

fire by blowing with a blast from the double bellows for half an hour,

because copper which is devoid of lead requires this time to become hot

and to melt; copper not devoid of lead melts quicker. When he has blown

the bellows for about the space of time stated, he removes the glowing

charcoal with the tongs, and stirs the copper with a splinter of wood,

which he grasps with the tongs. If it does not stir easily, it is a sign

that the copper is not wholly liquefied; if he finds this is the case,

he again places a large piece of charcoal in the crucible, and replaces

the glowing charcoal which had been removed, and again blows the bellows

for a short time. When all the copper has melted he stops using the

bellows, for if he were to continue to use them, the fire would consume

part of the copper, and then that which remained would be richer than

the cake from which it had been cut; this is no small mistake.

Therefore, as soon as the copper has become sufficiently liquefied, he

pours it out into a little iron mould, which may be large or small,

according as more or less copper is melted in the crucible for the

purpose of the assay. The mould has a handle, likewise made of iron, by

which it is held when the copper is poured in, after which, he plunges

it into a tub of water placed near at hand, that the copper may be

cooled. Then he again dries the copper by the fire, and cuts off its

point with an iron wedge; the portion nearest the point he hammers on an

anvil and makes into a leaf, which he cuts into pieces.

[Illustration 250 (Copper Mould for Assaying): A--Iron mould. B--Its

handle.]

Others stir the molten copper with a stick of linden tree charcoal, and

then pour it over a bundle of new clean birch twigs, beneath which is

placed a wooden tub of sufficient size and full of water, and in this

manner the copper is broken up into little granules as small as hemp

seeds. Others employ straw in place of twigs. Others place a broad stone

in a tub and pour in enough water to cover the stone, then they run out

the molten copper from the crucible on to the stone, from which the

minute granules roll off; others pour the molten copper into water and

stir it until it is resolved into granules. The fire does not easily

melt the copper in the cupel unless it has been poured and a thin leaf

made of it, or unless it has been resolved into granules or made into

filings; and if it does not melt, all the labour has been undertaken in

vain. In order that they may be accurately weighed out, silver and lead

are resolved into granules in the same manner as copper. But to return

to the assay of copper. When the copper has been prepared by these

methods, if it is free of lead and iron, and rich in silver, to each

_centumpondium_ (lesser weights) add one and a half _unciae_ of lead

(larger weights). If, however, the copper contains some lead, add one

_uncia_ of lead; if it contains iron, add two _unciae_. First put the

lead into a cupel, and after it begins to smoke, add the copper; the

fire generally consumes the copper, together with the lead, in about one

hour and a quarter. When this is done, the silver will be found in the

bottom of the cupel. The fire consumes both of those metals more quickly

if they are heated in that furnace which draws in air. It is better to

cover the upper half of it with a lid, and not only to put on the muffle

door, but also to close the window of the muffle door with a piece of

charcoal, or with a piece of brick. If the copper be such that the

silver can only be separated from it with difficulty, then before it is

tested with fire in the cupel, lead should first be put into the

scorifier, and then the copper should be added with a moderate quantity

of melted salt, both that the lead may absorb the copper and that the

copper may be cleansed of the dross which abounds in it.

Tin which contains silver should not at the beginning of the assay be

placed in a cupel, lest the silver, as often happens, be consumed and

converted into fumes, together with the tin. As soon as the lead[35] has

begun to fume in the scorifier, then add that[36] to it. In this way the

lead will take the silver and the tin will boil and turn into ashes,

which may be removed with a wooden splinter. The same thing occurs if

any alloy is melted in which there is tin. When the lead has absorbed

the silver which was in the tin, then, and not till then, it is heated

in the cupel. First place the lead with which the silver is mixed, in an

iron pan, and stand it on a hot furnace and let it melt; afterward pour

this lead into a small iron mould, and then beat it out with a hammer on

an anvil and make it into leaves in the same way as the copper. Lastly,

place it in the cupel, which assay can be carried out in the space of

half an hour. A great heat is harmful to it, for which reason there is

no necessity either to cover the half of the furnace with a lid or to

close up its mouth.

The minted metal alloys, which are known as money, are assayed in the

following way. The smaller silver coins which have been picked out from

the bottom and top and sides of a heap are first carefully cleansed;

then, after they have been melted in the triangular crucible, they are

either resolved into granules, or made into thin leaves. As for the

large coins which weigh a _drachma_, a _sicilicus_, half an _uncia_, or

an _uncia_, beat them into leaves. Then take a _bes_ of the granules, or

an equal weight of the leaves, and likewise take another _bes_ in the

same way. Wrap each sample separately in paper, and afterwards place two

small pieces of lead in two cupels which have first been heated. The

more precious the money is, the smaller portion of lead do we require

for the assay, the more base, the larger is the portion required; for if

a _bes_ of silver is said to contain only half an _uncia_ or one _uncia_

of copper, we add to the _bes_ of granules half an _uncia_ of lead. If

it is composed of equal parts of silver and copper, we add an _uncia_ of

lead, but if in a _bes_ of copper there is only half an _uncia_ or one

_uncia_ of silver, we add an _uncia_ and a half of lead. As soon as the

lead has begun to fume, put into each cupel one of the papers in which

is wrapped the sample of silver alloyed with copper, and close the mouth

of the muffle with charcoal. Heat them with a gentle fire until all the

lead and copper are consumed, for a hot fire by its heat forces the

silver, combined with a certain portion of lead, into the cupel, in

which way the assay is rendered erroneous. Then take the beads out of

the cupel and clean them of dross. If neither depresses the pan of the

balance in which it is placed, but their weight is equal, the assay has

been free from error; but if one bead depresses its pan, then there is

an error, for which reason the assay must be repeated. If the _bes_ of

coin contains but seven _unciae_ of pure silver it is because the King,

or Prince, or the State who coins the money, has taken one _uncia_,

which he keeps partly for profit and partly for the expense of coining,

he having added copper to the silver. Of all these matters I have

written extensively in my book _De Precio Metallorum et Monetis_.

We assay gold coins in various ways. If there is copper mixed with the

gold, we melt them by fire in the same way as silver coins; if there is

silver mixed with the gold, they are separated by the strongest _aqua

valens_; if there is copper and silver mixed with the gold, then in the

first place, after the addition of lead, they are heated in the cupel

until the fire consumes the copper and the lead, and afterward the gold

is parted from the silver.

It remains to speak of the touchstone[37] with which gold and silver are

tested, and which was also used by the Ancients. For although the assay

made by fire is more certain, still, since we often have no furnace, nor

muffle, nor crucibles, or some delay must be occasioned in using them,

we can always rub gold or silver on the touchstone, which we can have in

readiness. Further, when gold coins are assayed in the fire, of what use

are they afterward? A touchstone must be selected which is thoroughly

black and free of sulphur, for the blacker it is and the more devoid of

sulphur, the better it generally is; I have written elsewhere of its

nature[38]. First the gold is rubbed on the touchstone, whether it

contains silver or whether it is obtained from the mines or from the

smelting; silver also is rubbed in the same way. Then one of the

needles, that we judge by its colour to be of similar composition, is

rubbed on the touchstone; if this proves too pale, another needle which

has a stronger colour is rubbed on the touchstone; and if this proves

too deep in colour, a third which has a little paler colour is used. For

this will show us how great a proportion of silver or copper, or silver

and copper together, is in the gold, or else how great a proportion of

copper is in silver.

These needles are of four kinds.[39] The first kind are made of gold and

silver, the second of gold and copper, the third of gold, silver, and

copper, and the fourth of silver and copper. The first three kinds of

needles are used principally for testing gold, and the fourth for

silver. Needles of this kind are prepared in the following ways. The

lesser weights correspond proportionately to the larger weights, and

both of them are used, not only by mining people, but by coiners also.

The needles are made in accordance with the lesser weights, and each set

corresponds to a _bes_, which, in our own vocabulary, is called a

_mark_. The _bes_, which is employed by those who coin gold, is divided

into twenty-four double _sextulae_, which are now called after the

Greek name _ceratia_; and each double _sextula_ is divided into four

_semi-sextulae_, which are called _granas_; and each _semi-sextula_ is

divided into three units of four _siliquae_ each, of which each unit is

called a _grenlin_. If we made the needles to be each four _siliquae_,

there would be two hundred and eighty-eight in a _bes_, but if each were

made to be a _semi-sextula_ or a double _scripula_, then there would be

ninety-six in a _bes_. By these two methods too many needles would be

made, and the majority of them, by reason of the small difference in the

proportion of the gold, would indicate nothing, therefore it is

advisable to make them each of a double _sextula_; in this way

twenty-four needles are made, of which the first is made of twenty-three

_duellae_ of silver and one of gold. Fannius is our authority that the

Ancients called the double _sextula_ a _duella_. When a bar of silver is

rubbed on the touchstone and colours it just as this needle does, it

contains one _duella_ of gold. In this manner we determine by the other

needles what proportion of gold there is, or when the gold exceeds the

silver in weight, what proportion of silver.

[Illustration 255 (Touch-needles)]

The needles are made[40]:--

The 1st needle of 23 _duellae_ of silver and 1 _duella_ of gold.

" 2nd " 22 " " 2 _duellae_ of gold.

" 3rd " 21 " " 3 " "

" 4th " 20 " " 4 " "

" 5th " 19 " " 5 " "

" 6th " 18 " " 6 " "

" 7th " 17 " " 7 " "

" 8th " 16 " " 8 " "

" 9th " 15 " " 9 " "

" 10th " 14 " " 10 " "

" 11th " 13 " " 11 " "

" 12th " 12 " " 12 " "

" 13th " 11 " " 13 " "

" 14th " 10 " " 14 " "

" 15th " 9 " " 15 " "

" 16th " 8 " " 16 " "

" 17th " 7 " " 17 " "

" 18th " 6 " " 18 " "

" 19th " 5 " " 19 " "

" 20th " 4 " " 20 " "

" 21st " 3 " " 21 " "

" 22nd " 2 " " 22 " "

" 23rd " 1 " " 23 " "

" 24th " pure gold

By the first eleven needles, when they are rubbed on the touchstone, we

test what proportion of gold a bar of silver contains, and with the

remaining thirteen we test what proportion of silver is in a bar of

gold; and also what proportion of either may be in money.

Since some gold coins are composed of gold and copper, thirteen needles

of another kind are made as follows:--

The 1st of 12 _duellae_ of gold and 12 _duellae_ of copper.

" 2nd " 13 " " 11 " "

" 3rd " 14 " " 10 " "

" 4th " 15 " " 9 " "

" 5th " 16 " " 8 " "

" 6th " 17 " " 7 " "

" 7th " 18 " " 6 " "

" 8th " 19 " " 5 " "

" 9th " 20 " " 4 " "

" 10th " 21 " " 3 " "

" 11th " 22 " " 2 " "

" 12th " 23 " " 1 " "

" 13th " pure gold.

These needles are not much used, because gold coins of that kind are

somewhat rare; the ones chiefly used are those in which there is much

copper. Needles of the third kind, which are composed of gold, silver,

and copper, are more largely used, because such gold coins are common.

But since with the gold there are mixed equal or unequal portions of

silver and copper, two sorts of needles are made. If the proportion of

silver and copper is equal, the needles are as follows:--

Gold. Silver. Copper.

The 1st of 12 _duellae_ 6 _duellae_ 0 _sextula_ 6 _duellae_ 0 _sextula_

" 2nd " 13 " 5 " 1 " 5 " 1 "

" 3rd " 14 " 5 " 5 "

" 4th " 15 " 4 " 1 " 4 " 1 "

" 5th " 16 " 4 " 4 "

" 6th " 17 " 3 " 1 " 3 " 1 "

" 7th " 18 " 3 " 3 "

" 8th " 19 " 2 " 1 " 2 " 1 "

" 9th " 20 " 2 " 2 "

" 10th " 21 " 1 " 1 " 1 " 1 "

" 11th " 22 " 1 " 1 "

" 12th " 23 " 1 "

" 13th " pure gold.

Some make twenty-five needles, in order to be able to detect the two

_scripula_ of silver or copper which are in a _bes_ of gold. Of these

needles, the first is composed of twelve _duellae_ of gold and six of

silver, and the same number of copper. The second, of twelve _duellae_

and one _sextula_ of gold and five _duellae_ and one and a half

_sextulae_ of silver, and the same number of _duellae_ and one and a

half _sextulae_ of copper. The remaining needles are made in the same

proportion.

Pliny is our authority that the Romans could tell to within one

_scripulum_ how much gold was in any given alloy, and how much silver or

copper.

Needles may be made in either of two ways, namely, in the ways of which

I have spoken, and in the ways of which I am now about to speak. If

unequal portions of silver and copper have been mixed with the gold,

thirty-seven needles are made in the following way:--

Gold. Silver. Copper.

_Duellae_. _Duellae_ _Duellae_

_Sextulae_ _Sextulae_

_Siliquae_. _Siliquae_.

The 1st of 12 9 0 0 3 0 0

" 2nd " 12 8 0 0 4 0 0

" 3rd " 12 7 5

" 4th " 13 8 1/2 2 1/2

" 5th " 13 7 1/2 4 3 1 8

" 6th " 13 6 1/2 8 4 1 4

" 7th " 14 7 1 2 1

" 8th " 14 6 1 8 3 1/2 4

" 9th " 14 5 1-1/2 4 4 8

" 10th " 15 6 1-1/2 2 1/2

" 11th " 15 6 3

" 12th " 15 5 1/2 3 1-1/2

" 13th " 16 6 2

" 14th " 16 5 1/2 4 2 1 8

" 15th " 16 4 1 8 3 1/2 4

" 16th " 17 5 1/2 0 1 1-1/2

" 17th " 17 4 1 8 2 1/2 4

" 18th " 17 4 4 2 1-1/2 8

" 19th " 18 4 1 1 1

" 20th " 18 4 0 2

" 21st " 18 3 1 2 1

" 22nd " 19 2 1-1/2 1 1/2

" 23rd " 19 3 1/2 4 1 1 8

" 24th " 19 2 1-1/2 8 2 4

" 25th " 20 3 1

" 26th " 20 2 1 8 1 1/2 4

" 27th " 20 2 1/2 4 1 1 8

" 28th " 21 2 1/2 1-1/2

" 29th " 21 2 1

" 30th " 21 1 1-1/2 1 1/2

" 31st " 22 1 1 1

" 32nd " 22 1 1/2 4 0 1 8

" 33rd " 22 1 8 1-1/2 4

" 34th " 23 1-1/2 1/2

" 35th " 23 1 8 1/2 4

" 36th " 23 1 4 1/2 8

" 37th " pure gold.

Since it is rarely found that gold, which has been coined, does not

amount to at least fifteen _duellae_ gold in a _bes_, some make only

twenty-eight needles, and some make them different from those already

described, inasmuch as the alloy of gold with silver and copper is

sometimes differently proportioned.

These needles are made:--

Gold. Silver. Copper.

_Duellae_. _Duellae_ _Duellae_

_Sextulae_ _Sextulae_

_Siliquae_. _Siliquae_.

The 1st of 15 6 1 8 2 1/2 4

" 2nd " 15 6 4 2 1-1/2 8

" 3rd " 15 5 1/2 3 1-1/2

" 4th " 16 6 1/2 1 1-1/2

" 5th " 16 5 1 8 2 1/2 4

" 6th " 16 4 1-1/2 8 3 4

" 7th " 17 5 1 4 1 1/2 8

" 8th " 17 5 4 1 1-1/2 8

" 9th " 17 4 1 4 2 1/2 8

" 10th " 18 4 1 1 1

" 11th " 18 4 2

" 12th " 18 3 1 2 1

" 13th " 19 3 1-1/2 4 1 8

" 14th " 19 3 1/2 4 1 1 8

" 15th " 19 2 1-1/2 4 2 8

" 16th " 20 3 1

" 17th " 20 2 1 1

" 18th " 20 2 2

" 19th " 21 2 1/2 4 1 8

" 20th " 21 1 1-1/2 4 1 8

" 21st " 21 1 1 8 1 1/2 4

" 22nd " 22 1 1 8 1/2 4

" 23rd " 22 1 1 1

" 24th " 22 1 1/2 4 1 8

" 25th " 23 1-1/2 4 8

" 26th " 23 1-1/2 1/2

" 27th " 23 1 8 1/2 4

" 28th " pure gold

Next follows the fourth kind of needles, by which we test silver coins

which contain copper, or copper coins which contain silver. The _bes_ by

which we weigh the silver is divided in two different ways. It is either

divided twelve times, into units of five _drachmae_ and one _scripulum_

each, which the ordinary people call _nummi_[41]; each of these units

we again divide into twenty-four units of four _siliquae_ each, which

the same ordinary people call a _grenlin_; or else the _bes_ is divided

into sixteen _semunciae_ which are called _loths_, each of which is

again divided into eighteen units of four _siliquae_ each, which they

call _grenlin_. Or else the _bes_ is divided into sixteen _semunciae_,

of which each is divided into four _drachmae_, and each _drachma_ into

four _pfennige_. Needles are made in accordance with each method of

dividing the _bes_. According to the first method, to the number of

twenty-four half _nummi_; according to the second method, to the number

of thirty-one half _semunciae_, that is to say a _sicilicus_; for if the

needles were made to the number of the smaller weights, the number of

needles would again be too large, and not a few of them, by reason of

the small difference in proportion of silver or copper, would have no

significance. We test both bars and coined money composed of silver and

copper by both scales. The one is as follows: the first needle is made

of twenty-three parts of copper and one part silver; whereby, whatsoever

bar or coin, when rubbed on the touchstone, colours it just as this

needle does, in that bar or money there is one twenty-fourth part of

silver, and so also, in accordance with the proportion of silver, is

known the remaining proportion of the copper.

The 1st needle is made of 23 parts of copper and 1 of silver.

" 2nd " " 22 " " 2 "

" 3rd " " 21 " " 3 "

" 4th " " 20 " " 4 "

" 5th " " 19 " " 5 "

" 6th " " 18 " " 6 "

" 7th " " 17 " " 7 "

" 8th " " 16 " " 8 "

" 9th " " 15 " " 9 "

" 10th " " 14 " " 10 "

" 11th " " 13 " " 11 "

" 12th " " 12 " " 12 "

" 13th " " 11 " " 13 "

" 14th " " 10 " " 14 "

" 15th " " 9 " " 15 "

" 16th " " 8 " " 16 "

" 17th " " 7 " " 17 "

" 18th " " 6 " " 18 "

" 19th " " 5 " " 19 "

" 20th " " 4 " " 20 "

" 21st " " 3 " " 21 "

" 22nd " " 2 " " 22 "

" 23rd " " 1 " " 23 "

" 24th of pure silver.

The other method of making needles is as follows:--

Copper. Silver.

_Semunciae_ _Sicilici._ _Semunciae_ _Sicilici._

The 1st is of 15 1

" 2nd " " 14 1 1 1

" 3rd " " 14 2

" 4th " " 13 1 2 1

" 5th " " 13 3

" 6th " " 12 1 3 1

" 7th " " 12 4

" 8th " " 11 1 4 1

" 9th " " 11 5

" 10th " " 10 1 5 1

" 11th " " 10 6

" 12th " " 9 1 6 1

" 13th " " 9 7

" 14th " " 8 1 7 1

" 15th " " 8 8

" 16th " " 7 1 8 1

" 17th " " 7 9

" 18th " " 6 1 9 1

" 19th " " 6 10

" 20th " " 5 1 10 1

" 21st " " 5 11

" 22nd " " 4 1 11 1

" 23rd " " 4 12

" 24th " " 3 1 12 1

" 25th " " 3 13

" 26th " " 2 1 13 1

" 27th " " 2 14

" 28th " " 1 1 14 1

" 29th " " 1 15

" 30th " " 1 15 1

" 31st of pure silver.

So much for this. Perhaps I have used more words than those most highly

skilled in the art may require, but it is necessary for the

understanding of these matters.

I will now speak of the weights, of which I have frequently made

mention. Among mining people these are of two kinds, that is, the

greater weights and the lesser weights. The _centumpondium_ is the first

and largest weight, and of course consists of one hundred _librae_, and

for that reason is called a hundred weight.

The various weights are:--

1st = 100 _librae_ = _centumpondium_.

2nd = 50 "

3rd = 25 "

4th = 16 "

5th = 8 "

6th = 4 "

7th = 2 "

8th = 1 _libra_.

This _libra_ consists of sixteen _unciae_, and the half part of the

_libra_ is the _selibra_, which our people call a _mark_, and consists

of eight _unciae_, or, as they divide it, of sixteen _semunciae_:--

9th = 8 _unciae_.

10th = 8 _semunciae_.

11th = 4 "

12th = 2 "

13th = 1 _semuncia_.

14th = 1 _sicilicus_.

15th = 1 _drachma_.

16th = 1 _dimidi-drachma_.

[Illustration 262 (Weights for Assay Balances)]

The above is how the "greater" weights are divided. The "lesser" weights

are made of silver or brass or copper. Of these, the first and largest

generally weighs one _drachma_, for it is necessary for us to weigh, not

only ore, but also metals to be assayed, and smaller quantities of lead.

The first of these weights is called a _centumpondium_ and the number of

_librae_ in it corresponds to the larger scale, being likewise one

hundred[42].

The 1st is called 1 _centumpondium_.

" 2nd " 50 _librae_.

" 3rd " 25 "

" 4th " 16 "

" 5th " 8 "

" 6th " 4 "

" 7th " 2 "

" 8th " 1 "

" 9th " 1 _selibra_.

" 10th " 8 _semunciae_.

" 11th " 4 "

" 12th " 2 "

" 13th " 1 "

" 14th " 1 _sicilicus_.

The fourteenth is the last, for the proportionate weights which

correspond with a _drachma_ and half a _drachma_ are not used. On all

these weights of the lesser scale, are written the numbers of _librae_

and of _semunciae_. Some copper assayers divide both the lesser and

greater scale weights into divisions of a different scale. Their largest

weight of the greater scale weighs one hundred and twelve _librae_,

which is the first unit of measurement.

1st = 112 _librae_.

2nd = 64 "

3rd = 32 "

4th = 16 "

5th = 8 "

6th = 4 "

7th = 2 "

8th = 1 "

9th = 1 _selibra_ or sixteen _semunciae_.

10th = 8 _semunciae_.

11th = 4 "

12th = 2 "

13th = 1 "

As for the _selibra_ of the lesser weights, which our people, as I have

often said, call a _mark_, and the Romans call a _bes_, coiners who coin

gold, divide it just like the greater weights scale, into twenty-four

units of two _sextulae_ each, and each unit of two _sextulae_ is divided

into four _semi-sextulae_ and each _semi-sextula_ into three units of

four _siliquae_ each. Some also divide the separate units of four

_siliquae_ into four individual _siliquae_, but most, omitting the

_semi-sextulae_, then divide the double _sextula_ into twelve units of

four _siliquae_ each, and do not divide these into four individual

_siliquae_. Thus the first and greatest unit of measurement, which is

the _bes_, weighs twenty-four double _sextulae_.

The 2nd = 12 double _sextulae_.

" 3rd = 6 " "

" 4th = 3 " "

" 5th = 2 " "

" 6th = 1 " "

" 7th = 2 _semi-sextulae_ or four _semi-sextulae_.

" 8th = 1 _semi-sextula_ or 3 units of 4 _siliquae_ each.

" 9th = 2 units of four _siliquae_ each.

" 10th = 1 " " "

Coiners who mint silver also divide the _bes_ of the lesser weights in

the same way as the greater weights; our people, indeed, divide it into

sixteen _semunciae_, and the _semuncia_ into eighteen units of four

_siliquae_ each.

There are ten weights which are placed in the other pan of the balance,

when they weigh the silver which remains from the copper that has been

consumed, when they assay the alloy with fire.

The 1st = 16 _semunciae_ = 1 _bes_.

" 2nd = 8 "

" 3rd = 4 "

" 4th = 2 "

" 5th = 1 " or 18 units of 4 _siliquae_ each.

" 6th = 9 units of 4 _siliquae_ each.

" 7th = 6 " "

" 8th = 3 " "

" 9th = 2 " "

" 10th = 1 " "

The coiners of Nuremberg who mint silver, divide the _bes_ into sixteen

_semunciae_, but divide the _semuncia_ into four _drachmae_, and the

_drachma_ into four _pfennige_. They employ nine weights.

The 1st = 16 _semunciae_.

" 2nd = 8 "

" 3rd = 4 "

" 4th = 2 "

" 5th = 1 "

For they divide the _bes_ in the same way as our own people, but since

they divide the _semuncia_ into four _drachmae_,

the 6th weight = 2 _drachmae_.

" 7th " = 1 _drachma_ or 4 _pfennige_.

" 8th " = 2 _pfennige_.

" 9th " = 1 _pfennig_.

The men of Cologne and Antwerp[43] divide the _bes_ into twelve units of

five _drachmae_ and one _scripulum_, which weights they call _nummi_.

Each of these they again divide into twenty-four units of four

_siliquae_ each, which they call _grenlins_. They have ten weights, of

which

the 1st = 12 _nummi_ = 1 _bes_.

" 2nd = 6 "

" 3rd = 3 "

" 4th = 2 "

" 5th = 1 " = 24 units of 4 _siliquae_ each.

" 6th = 12 units of 4 _siliquae_ each.

" 7th = 6 " "

" 8th = 3 " "

" 9th = 2 " "

" 10th = 1 " "

And so with them, just as with our own people, the _mark_ is divided

into two hundred and eighty-eight _grenlins_, and by the people of

Nuremberg it is divided into two hundred and fifty-six _pfennige_.

Lastly, the Venetians divide the _bes_ into eight _unciae_. The _uncia_

into four _sicilici_, the _sicilicus_ into thirty-six _siliquae_. They

make twelve weights, which they use whenever they wish to assay alloys

of silver and copper. Of these

the 1st = 8 _unciae_ = 1 _bes_.

" 2nd = 4 "

" 3rd = 2 "

" 4th = 1 " or 4 _sicilici_.

" 5th = 2 _sicilici_.

" 6th = 1 _sicilicus_.

" 7th = 18 _siliquae_.

" 8th = 9 "

" 9th = 6 "

" 10th = 3 "

" 11th = 2 "

" 12th = 1 "

Since the Venetians divide the _bes_ into eleven hundred and fifty-two

_siliquae_, or two hundred and eighty-eight units of 4 _siliquae_ each,

into which number our people also divide the _bes_, they thus make the

same number of _siliquae_, and both agree, even though the Venetians

divide the _bes_ into smaller divisions.

This, then, is the system of weights, both of the greater and the lesser

kinds, which metallurgists employ, and likewise the system of the lesser

weights which coiners and merchants employ, when they are assaying

metals and coined money. The _bes_ of the larger weight with which they

provide themselves when they weigh large masses of these things, I have

explained in my work _De Mensuris et Ponderibus_, and in another book,

_De Precio Metallorum et Monetis_.

[Illustration 265 (Balances): A--First small balance. B--Second.

C--Third, placed in a case.]

There are three small balances by which we weigh ore, metals, and

fluxes. The first, by which we weigh lead and fluxes, is the largest

among these smaller balances, and when eight _unciae_ (of the greater

weights) are placed in one of its pans, and the same number in the

other, it sustains no damage. The second is more delicate, and by this

we weigh the ore or the metal, which is to be assayed; this is well able

to carry one _centumpondium_ of the lesser weights in one pan, and in

the other, ore or metal as heavy as that weight. The third is the most

delicate, and by this we weigh the beads of gold or silver, which, when

the assay is completed, settle in the bottom of the cupel. But if anyone

weighs lead in the second balance, or an ore in the third, he will do

them much injury.

Whatsoever small amount of metal is obtained from a _centumpondium_ of

the lesser weights of ore or metal alloy, the same greater weight of

metal is smelted from a _centumpondium_ of the greater weight of ore or

metal alloy.

END OF BOOK VII.

FOOTNOTES:

[1] We have but little record of anything which could be called

"assaying" among the Greeks and Romans. The fact, however, that they

made constant use of the touchstone (see note 37, p. 252) is sufficient

proof that they were able to test the purity of gold and silver. The

description of the touchstone by Theophrastus contains several

references to "trial" by fire (see note 37, p. 252). They were adepts at

metal working, and were therefore familiar with melting metals on a

small scale, with the smelting of silver, lead, copper, and tin ores

(see note 1, p. 353) and with the parting of silver and lead by

cupellation. Consequently, it would not require much of an imaginative

flight to conclude that there existed some system of tests of ore and

metal values by fire. Apart from the statement of Theophrastus referred

to, the first references made to anything which might fill the _role_ of

assaying are from the Alchemists, particularly Geber (prior to 1300),

for they describe methods of solution, precipitation, distillation,

fusing in crucibles, cupellation, and of the parting of gold and silver

by acid and by sulphur, antimony, or cementation. However, they were not

bent on determining quantitative values, which is the fundamental object

of the assayer's art, and all their discussion is shrouded in an obscure

cloak of gibberish and attempted mysticism. Nevertheless, therein lies

the foundation of many cardinal assay methods, and even of chemistry

itself.

The first explicit records of assaying are the anonymous booklets

published in German early in the 16th Century under the title

_Probierbuechlein_. Therein the art is disclosed well advanced toward

maturity, so far as concerns gold and silver, with some notes on lead

and copper. We refer the reader to Appendix B for fuller discussion of

these books, but we may repeat here that they are a collection of

disconnected recipes lacking in arrangement, the items often repeated,

and all apparently the inheritance of wisdom passed from father to son

over many generations. It is obviously intended as a sort of reminder to

those already skilled in the art, and would be hopeless to a novice.

Apart from some notes in Biringuccio (Book III, Chaps. 1 and 2) on

assaying gold and silver, there is nothing else prior to _De Re

Metallica_. Agricola was familiar with these works and includes their

material in this chapter. The very great advance which his account

represents can only be appreciated by comparison, but the exhaustive

publication of other works is foreign to the purpose of these notes.

Agricola introduces system into the arrangement of his materials,

describes implements, and gives a hundred details which are wholly

omitted from the previous works, all in a manner which would enable a

beginner to learn the art. Furthermore, the assaying of lead, copper,

tin, quicksilver, iron, and bismuth, is almost wholly new, together with

the whole of the argument and explanations. We would call the attention

of students of the history of chemistry to the general oversight of

these early 16th Century attempts at analytical chemistry, for in them

lie the foundations of that science. The statement sometimes made that

Agricola was the first assayer, is false if for no other reason than

that science does not develop with such strides at any one human hand.

He can, however, fairly be accounted as the author of the first proper

text-book upon assaying. Those familiar with the art will be astonished

at the small progress made since his time, for in his pages appear most

of the reagents and most of the critical operations in the dry analyses

of gold, silver, lead, copper, tin, bismuth, quicksilver, and iron of

to-day. Further, there will be recognised many of the "kinks" of the art

used even yet, such as the method of granulation, duplicate assays, the

"assay ton" method of weights, the use of test lead, the introduction of

charges in leaf lead, and even the use of beer instead of water to damp

bone-ash.

The following table is given of the substances mentioned requiring some

comment, and the terms adopted in this book, with notes for convenience

in reference. The German terms are either from Agricola's Glossary of

_De Re Metallica_, his _Interpretatio_, or the German Translation. We

have retained the original German spelling. The fifth column refers to

the page where more ample notes are given:--

Terms Latin. German. Remarks. Further

adopted. Notes.

Alum _Alumen_ _Alaun_ Either potassium p. 564

or ammonia alum

Ampulla _Ampulla_ _Kolb_ A distillation jar

Antimony _Stibium_ _Spiesglas_ Practically always p. 428

antimony sulphide

_Aqua valens_ _Aqua valens_ _Scheidewasser_ Mostly nitric acid p. 439

or _aqua_

Argol _Feces vini _Die Crude tartar p. 234

siccae_ weinheffen_

Ash of lead _Nigrum Artificial lead p. 237

plumbum sulphide

cinereum_

Ash of musk ivy _Sal ex _Salalkali_ Mostly potash p. 560

(Salt made anthyllidis

from) cinere factus_

Ashes which _Cineres quo Mostly potash p. 559

wool-dyers use infectores

lanarum

utuntur_

Assay _Venas experiri_ _Probiren_

Assay furnace _Fornacula_ _Probir ofen_ "Little" furnace

Azure _Caeruleum_ _Lasur_ Partly copper p. 110

carbonate

(azurite)

partly silicate

Bismuth _Plumbum _Wismut_ _Bismuth_ p. 433

Cinereum_

Bitumen _Bitumen_ _Bergwachs_ p. 581

Blast furnace _Prima fornax_ _Schmeltzofen_

Borax _Chrysocolla ex _Borras; Tincar_ p. 560

nitro

confecta;

chrysocolla

quam boracem

nominant_

Burned alum _Alumen coctum_ _Gesottener Probably p. 565

alaun_ dehydrated alum

_Cadmia_ (1) Furnace p. 112

(see note accretions (2)

8, p. 112) Calamine (3) Zinc

blende (4) Cobalt

arsenical sulphides

Camphor _Camphora_ _Campffer_ p. 238

Chrysocolla

called borax

(see borax)

Chrysocolla _Chrysocolla_ _Berggruen und Partly p. 110

(copper Schifergruen_ chrysocolla,

mineral) partly malachite

Copper filings _Aeris scobs _Kupferfeilich_ Apparently finely p. 233

elimata_ divided copper

metal

Copper flowers _Aeris flos_ _Kupferbraun_ Cupric oxide p. 538

Copper scales _Aeris squamae_ _Kupfer Probably cupric

hammerschlag oxide

oder kessel

braun_

Copper

minerals (see

note 8,

p. 109)

Crucible _Catillus _Dreieckicht- See illustration p. 229

(triangular) triangularis_ schirbe_

Cupel _Catillus _Capelle_

cinereus_

Cupellation _Secunda _Treibherd_

furnace fornax_

Flux _Additamentum_ _Zusetze_ p. 232

Furnace _Cadmia _Mitlere und

accretions fornacum_ obere

offenbrueche_

Galena _Lapis _Glantz_ Lead sulphide p. 110

plumbarius_

Glass-gall _Recrementum _Glassgallen_ Skimmings from p. 235

vitri_ glass melting

Grey antimony or _Stibi_ or _Spiesglas_ Antimony sulphide, p. 428

stibium _stibium_ stibnite

Hearth-lead _Molybdaena_ _Herdplei_ The saturated p. 476

furnace bottoms

from cupellation

Hoop (iron) _Circulus _Ring_ A forge for p. 226

ferreus_ crucibles

Iron filings _Ferri scobs _Eisen feilich_ Metallic iron

elimata_

Iron scales _Squamae ferri_ _Eisen Partly iron oxide

hammerschlag_

Iron slag _Recrementum _Sinder_

ferri_

Lead ash _Cinis plumbi _Pleiasche_ Artificial lead p. 237

nigri_ sulphide

Lead granules _Globuli _Gekornt plei_ Granulated lead

plumbei_

Lead ochre _Ochra _Pleigeel_ Modern massicot p. 232

plumbaria_ (PbO)

Lees of _aqua_ _Feces aquarum _Scheidewasser Uncertain p. 234

which separates quae aurum ab heffe_

gold from argento

silver secernunt_

Dried lees of _Siccae feces _Heffe des Argol p. 234

vinegar aceti_ essigs_

Dried lees of _Feces vini _Wein heffen_ Argol p. 234

wine siccae_

Limestone _Saxum calcis_ _Kalchstein_

Litharge _Spuma argenti_ _Glette_

Lye _Lixivium_ _Lauge durch Mostly potash p. 233

asschen

gemacht_

Muffle _Tegula_ _Muffel_ Latin, literally

"Roof-tile"

Operculum _Operculum_ _Helm oder Helmet or cover

alembick_ for a distillation

jar

Orpiment _Auripigmentum_ _Operment_ Yellow sulphide p. 111

of arsenic

(As_{2}S_{3})

Pyrites _Pyrites_ _Kis_ Rather a genus p. 112

of sulphides,

than iron

pyrite in

particular

Pyrites (Cakes _Panes ex _Stein_ Iron or Copper p. 350

from) pyrite matte

conflati_

Realgar _Sandaraca_ _Rosgeel_ Red sulphide of p. 111

arsenic (AsS)

Red lead _Minium_ _Menning_ Pb_{3}O_{4} p. 232

Roasted copper _Aes ustum_ _Gebrandt Artificial p. 233

kupffer_ copper

sulphide (?)

Salt _Sal_ _Saltz_ NaCl p. 233

Salt (Rock) _Sal fossilis_ _Berg saltz_ NaCl p. 233

_Sal _Sal A stock flux? p. 236

artificiosus_ artificiosus_

Sal ammoniac _Sal _Salarmoniac_ NH_{4}Cl p. 560

ammoniacus_

Saltpetre _Halinitrum_ _Salpeter_ KNO_{3} p. 561

Salt (refined) _Sal facticius NaCl

purgatus_

_Sal tostus_ _Sal tostus_ _Geroest saltz_ Apparently p. 233

simply heated or

melted common

salt

_Sal _Sal _Geroest saltz_ p. 233

torrefactus_ torrefactus_

Salt (melted) _Sal _Geflossen Melted salt or p. 233

liquefactus_ saltz_ salt glass

Scorifier _Catillus _Scherbe_

fictilis_

Schist _Saxum fissile_ _Schifer_

Silver minerals

(see note 8,

p. 108)

Slag _Recrementum_ _Schlacken_

Soda _Nitrum_ Mostly soda from p. 558

Egypt,

Na_{2}CO_{3}

Stones which _Lapides qui _Flues_ Quartz and p. 380

easily melt facile igni fluorspar

liquescunt_

Sulphur _Sulfur_ _Schwefel_ p. 579

_Tophus_ _Tophus_ _Topstein_ Marl(?) p. 233

Touchstone _Coticula_ _Goldstein_

Venetian glass _Venetianum

vitrum_

Verdigris _Aerugo _Gruenspan_ Copper p. 440

oder sub-acetate

Spanschgruen_

Vitriol _Atramentum _Kupferwasser_ Mostly FeSO_{4} p. 572

sutorium_

White schist _Saxum fissile _Weisser p. 234

album_ schifer_

Weights (see

Appendix).

[2] _Crudorum_,--unbaked?

[3] This reference is not very clear. Apparently the names refer to the

German terms _probier ofen_ and _windt ofen_.

[4] _Circulus_. This term does not offer a very satisfactory equivalent,

as such a furnace has no distinctive name in English. It is obviously a

sort of forge for fusing in crucibles.

[5] _Spissa_,--"Dry." This term is used in contra-distinction to

_pingue_, unctuous or "fatty."

[6] _Additamenta_,--"Additions." Hence the play on words.

We have adopted "flux" because the old English equivalent for all these

materials was "flux," although in modern nomenclature the term is

generally restricted to those substances which, by chemical combination

in the furnace, lower the melting point of some of the charge. The

"additions" of Agricola, therefore, include reducing, oxidizing,

sulphurizing, desulphurizing, and collecting agents as well as fluxes. A

critical examination of the fluxes mentioned in the next four pages

gives point to the Author's assertion that "some are of a very

complicated nature." However, anyone of experience with home-taught

assayers has come in contact with equally extraordinary combinations.

The four orders of "additions" enumerated are quite impossible to

reconcile from a modern metallurgical point of view.

[7] _Minium secundarium_. (_Interpretatio_,--_menning_. Pb_{3}O_{4}).

Agricola derived his Latin term from Pliny. There is great confusion in

the ancient writers on the use of the word _minium_, for prior to the

Middle Ages it was usually applied to vermilion derived from cinnabar.

Vermilion was much adulterated with red-lead, even in Roman times, and

finally in later centuries the name came to be appropriated to the lead

product. Theophrastus (103) mentions a substitute for vermilion, but, in

spite of commentators, there is no evidence that it was red-lead. The

first to describe the manufacture of real red-lead was apparently

Vitruvius (VII, 12), who calls it _sandaraca_ (this name was usually

applied to red arsenical sulphide), and says: "White-lead is heated in a

furnace and by the force of the fire becomes red lead. This invention

was the result of observation in the case of an accidental fire, and by

the process a much better material is obtained than from the mines." He

describes _minium_ as the product from cinnabar. Dioscorides (V, 63),

after discussing white-lead, says it may be burned until it becomes the

colour of _sandaracha_, and is called _sandyx_. He also states (V, 69)

that those are deceived who consider cinnabar to be the same as

_minium_, for _minium_ is made in Spain out of stone mixed with silver

sands. Therefore he is not in agreement with Vitruvius and Pliny on the

use of the term. Pliny (XXXIII, 40) says: "These barren stones

(apparently lead ores barren of silver) may be recognised by their

colour; it is only in the furnace that they turn red. After being

roasted it is pulverized and is _minium secundarium_. It is known to few

and is very inferior to the natural kind made from those sands we have

mentioned (_cinnabar_). It is with this that the genuine _minium_ is

adulterated in the works of the Company." This proprietary company who

held a monopoly of the Spanish quicksilver mines, "had many methods of

adulterating it (_minium_)--a source of great plunder to the Company."

Pliny also describes the making of red lead from white.

[8] _Ochra plumbaria_. (_Interpretatio_,--_pleigeel_; modern

German,--_Bleigelb_). The German term indicates that this "Lead Ochre,"

a form of PbO, is what in the English trade is known as _massicot_, or

_masticot_. This material can be a partial product from almost any

cupellation where oxidation takes place below the melting point of the

oxide. It may have been known to the Ancients among the various species

into which they divided litharge, but there is no valid reason for

assigning to it any special one of their terms, so far as we can see.

[9] There are four forms of copper named as re-agents by Agricola:

Copper filings _Aeris scobs elimata._

Copper scales _Aeris squamae._

Copper flowers _Aeris flos._

Roasted copper _Aes ustum._

The first of these was no doubt finely divided copper metal; the second,

third, and fourth were probably all cupric oxide. According to Agricola

(_De Nat. Fos._, p. 352), the scales were the result of hammering the

metal; the flowers came off the metal when hot bars were quenched in

water, and a third kind were obtained from calcining the metal. "Both

flowers (_flos_) and hammer-scales (_squama_) have the same properties

as _crematum_ copper.... The particles of flower copper are finer than

scales or _crematum_ copper." If we assume that the verb _uro_ used in

_De Re Metallica_ is of the same import as _cremo_ in the _De Natura

Fossilium_, we can accept this material as being merely cupric oxide,

but the _aes ustum_ of Pliny--Agricola's usual source of technical

nomenclature--is probably an artificial sulphide. Dioscorides (V, 47),

who is apparently the source of Pliny's information, says:--"Of _chalcos

cecaumenos_, the best is red, and pulverized resembles the colour of

cinnabar; if it turns black, it is over-burnt. It is made from broken

ship nails put into a rough earthen pot, with alternate layers of equal

parts of sulphur and salt. The opening should be smeared with potter's

clay and the pot put in the furnace until it is thoroughly heated," etc.

Pliny (XXXIV, 23) states: "Moreover Cyprian copper is roasted in crude

earthen pots with an equal amount of sulphur; the apertures of the pots

are well luted, and they are kept in the furnace until the pot is

thoroughly heated. Some add salt, others use _alumen_ instead of

sulphur, others add nothing, but only sprinkle it with vinegar."

[10] The reader is referred to note 6, p. 558, for more ample discussion

of the alkalis. Agricola gives in this chapter four substances of that

character:

Soda (_nitrum_). Lye. "Ashes which wool-dyers use." "Salt made

from the ashes of musk ivy."

The last three are certainly potash, probably impure. While the first

might be either potash or soda, the fact that the last three are

mentioned separately, together with other evidence, convinces us that by

the first is intended the _nitrum_ so generally imported into Europe

from Egypt during the Middle Ages. This imported salt was certainly the

natural bicarbonate, and we have, therefore, used the term "soda."

[11] In this chapter are mentioned seven kinds of common salt:

Salt _Sal._

Rock salt _Sal fossilis._

"Made" salt _Sal facticius._

Refined salt _Sal purgatius._

Melted salt _Sal liquefactus._

And in addition _sal tostus_ and _sal torrefactus_. _Sal facticius_ is

used in distinction from rock-salt. The melted salt would apparently be

salt-glass. What form the _sal tostus_ and _sal torrefactus_ could have

we cannot say, however, but they were possibly some form of heated salt;

they may have been combinations after the order of _sal artificiosus_

(see p. 236).

[12] "Stones which easily melt in hot furnaces and sand which is made

from them" (_lapides qui in ardentibus fornacibus facile liquescunt

arenae ab eis resolutae_). These were probably quartz in this instance,

although fluorspar is also included in this same genus. For fuller

discussion see note on p. 380.

[13] _Tophus_. (_Interpretatio_, _Toffstein oder topstein_). According

to Dana (Syst. of Min., p. 678), the German _topfstein_ was English

potstone or soapstone, a magnesian silicate. It is scarcely possible,

however, that this is what Agricola meant by this term, for such a

substance would be highly infusible. Agricola has a good deal to say

about this mineral in _De Natura Fossilium_ (p. 189 and 313), and from

these descriptions it would seem to be a tufaceous limestone of various

sorts, embracing some marls, stalagmites, calcareous sinter, etc. He

states: "Generally fire does not melt it, but makes it harder and breaks

it into powder. Tophus is said to be a stone found in caverns, made from

the dripping of stone juice solidified by cold ... sometimes it is found

containing many shells, and likewise the impressions of alder leaves;

our people make lime by burning it." Pliny, upon whom Agricola depends

largely for his nomenclature, mentions such a substance (XXXVI, 48):

"Among the multitude of stones there is _tophus_. It is unsuitable for

buildings, because it is perishable and soft. Still, however, there are

some places which have no other, as Carthage, in Africa. It is eaten

away by the emanations from the sea, crumbled to dust by the wind, and

washed away by the rain." In fact, _tophus_ was a wide genus among the

older mineralogists, Wallerius (_Meditationes Physico-Chemicae De

Origine Mundi_, Stockholm, 1776, p. 186), for instance, gives 22

varieties. For the purposes for which it is used we believe it was

always limestone of some form.

[14] _Saxum fissile album._ (_The Interpretatio_ gives the German as

_schifer_). Agricola mentions it in _Bermannus_ (459), in _De Natura

Fossilium_ (p. 319), but nothing definite can be derived from these

references. It appears to us from its use to have been either a

quartzite or a fissile limestone.

[15] Argol (_Feces vini siccae_,--"Dried lees of wine." Germ. trans.

gives _die wein heffen_, although the usual German term of the period

was _weinstein_). The lees of wine were the crude tartar or argols of

commerce and modern assayers. The argols of white wine are white, while

they are red from red wine. The white argol which Agricola so often

specifies would have no special excellence, unless it may be that it is

less easily adulterated. Agricola (_De Nat. Fos._, p. 344) uses the

expression "_Fex vini sicca_ called _tartarum_"--one of the earliest

appearances of the latter term in this connection. The use of argol is

very old, for Dioscorides (1st Century A.D.) not only describes argol,

but also its reduction to impure potash. He says (V, 90): "The lees

(_tryx_) are to be selected from old Italian wine; if not, from other

similar wine. Lees of vinegar are much stronger. They are carefully

dried and then burnt. There are some who burn them in a new earthen pot

on a large fire until they are thoroughly incinerated. Others place a

quantity of the lees on live coals and pursue the same method. The test

as to whether it is completely burned, is that it becomes white or blue,

and seems to burn the tongue when touched. The method of burning lees of

vinegar is the same.... It should be used fresh, as it quickly grows

stale; it should be placed in a vessel in a secluded place." Pliny

(XXIII, 31) says: "Following these, come the lees of these various

liquids. The lees of wine (_vini faecibus_) are so powerful as to be

fatal to persons on descending into the vats. The test for this is to

let down a lamp, which, if extinguished, indicates the peril.... Their

virtues are greatly increased by the action of fire." Matthioli,

commenting on this passage from Dioscorides in 1565, makes the following

remark (p. 1375): "The precipitate of the wine which settles in the

casks of the winery forms stone-like crusts, and is called by the

works-people by the name _tartarum_." It will be seen above that these

lees were rendered stronger by the action of fire, in which case the

tartar was reduced to potassium carbonate. The _weinstein_ of the old

German metallurgists was often the material lixiviated from the

incinerated tartar.

Dried lees of vinegar (_siccae feces aceti_; _Interpretatio_, _die heffe

des essigs_). This would also be crude tartar. Pliny (XXIII, 32) says:

"The lees of vinegar (_faex aceti_); owing to the more acrid material

are more aggravating in their effects.... When combined with

_melanthium_ it heals the bites of dogs and crocodiles."

[16] Dried lees of _aqua_ which separates gold and silver. (_Siccae

feces aquarum quae aurum ab argento secernunt_. German translation, _Der

scheidwasser heffe_). There is no pointed description in Agricola's

works, or in any other that we can find, as to what this material was.

The "separating _aqua_" was undoubtedly nitric acid (see p. 439, Book

X). There are two precipitates possible, both referred to as

_feces_,--the first, a precipitate of silver chloride from clarifying

the _aqua valens_, and the second, the residues left in making the acid

by distillation. It is difficult to believe that silver chloride was the

_feces_ referred to in the text, because such a precipitate would be

obviously misleading when used as a flux through the addition of silver

to the assays, too expensive, and of no merit for this purpose.

Therefore one is driven to the conclusion that the _feces_ must have

been the residues left in the retorts when nitric acid was prepared. It

would have been more in keeping with his usual mode of expression,

however, to have referred to this material as a _residuus_. The

materials used for making acid varied greatly, so there is no telling

what such a _feces_ contained. A list of possibilities is given in note

8, p. 443. In the main, the residue would be undigested vitriol, alum,

saltpetre, salt, etc., together with potassium, iron, and alum

sulphates. The _Probierbuechlin_ (p. 27) also gives this re-agent under

the term _Toden kopff das ist schlam oder feces auss dem scheydwasser_.

[17] _Recrementum vitri_. (_Interpretatio_, _Glassgallen_). Formerly,

when more impure materials were employed than nowadays, the surface of

the mass in the first melting of glass materials was covered with salts,

mostly potassium and sodium sulphates and chlorides which escaped

perfect vitrification. This "slag" or "_glassgallen_" of Agricola was

also termed _sandiver_.

[18] The whole of this expression is "_candidus, candido_." It is by no

means certain that this is tin, for usually tin is given as _plumbum

candidum_.

[19] _Sal artificiosus_. These are a sort of stock fluxes. Such mixtures

are common in all old assay books, from the _Probierbuechlin_ to later

than John Cramer in 1737 (whose Latin lectures on Assaying were

published in English under the title of "Elements of the Art of Assaying

Metals," London, 1741). Cramer observes (p. 51) that: "Artificers

compose a great many fluxes with the above-mentioned salts and with the

reductive ones; nay, some use as many different fluxes as there are

different ores and metals; all which, however, we think needless to

describe. It is better to have explained a few of the simpler ones,

which serve for all the others, and are very easily prepared, than to

tire the reader with confused compositions: and this chiefly because

unskilled artificers sometimes attempt to obtain with many ingredients

of the same nature heaped up beyond measure, and with much labour,

though not more properly and more securely, what might have been easily

effected, with one only and the same ingredient, thus increasing the

number, not at all the virtue of the things employed. Nevertheless, if

anyone loves variety, he may, according to the proportions and cautions

above prescribed, at his will chuse among the simpler kinds such as will

best suit his purpose, and compose a variety of fluxes with them."

[20] This operation apparently results in a coating to prevent the

deflagration of the saltpetre--in fact, it might be permitted to

translate _inflammatur_ "deflagrate," instead of kindle.

[21] The results which would follow from the use of these "fluxes" would

obviously depend upon the ore treated. They can all conceivably be

successful. Of these, the first is the lead-glass of the German

assayers--a flux much emphasized by all old authorities, including

Lohneys, Ercker and Cramner, and used even yet. The "powerful flux"

would be a reducing, desulphurizing, and an acid flux. The "more

powerful" would be a basic flux in which the reducing action of the

argols would be largely neutralised by the nitre. The "still more

powerful" would be a strongly sulphurizing basic flux, while the "most

powerful" would be a still more sulphurizing flux, but it is badly mixed

as to its oxidation and basic properties. (See also note 19 on _sal

artificiosus_).

[22] Lead ash (_Cinis Plumbi_. Glossary, _Pleyasch_).--This was

obviously, from the method of making, an artificial lead sulphide.

[23] Ashes of lead (_Nigri plumbi cinis_). This, as well as lead ash,

was also an artificial lead sulphide. Such substances were highly valued

by the Ancients for medicinal purposes. Dioscorides (V, 56) says:

"Burned lead (_Molybdos cecaumenos_) is made in this way: Sprinkle

sulphur over some very thinnest lead plates and put them into a new

earthen pot, add other layers, putting sulphur between each layer until

the pot is full; set it alight and stir the melted lead with an iron rod

until it is entirely reduced to ashes and until none of the lead remains

unburned. Then take it off, first stopping up your nose, because the

fumes of burnt lead are very injurious. Or burn the lead filings in a

pot with sulphur as aforesaid." Pliny (XXXIV., 50) gives much the same

directions.

[24] Camphor (_camphora_). This was no doubt the well-known gum.

Agricola, however, believed that camphor (_De Nat. Fossilium_, p. 224)

was a species of bitumen, and he devotes considerable trouble to the

refutation of the statements by the Arabic authors that it was a gum. In

any event, it would be a useful reducing agent.

[25] Inasmuch as orpiment and realgar are both arsenical sulphides, the

use of iron "slag," if it contains enough iron, would certainly matte

the sulphur and arsenic. Sulphur and arsenic are the "juices" referred

to (see note 4, p. 1). It is difficult to see the object of preserving

the antimony with such a sulphurizing "addition," unless it was desired

to secure a regulus of antimony alone from a given antimonial ore.

[26] The lead free from silver, called _villacense_, was probably from

Bleyberg, not far from Villach in Upper Austria, this locality having

been for centuries celebrated for its pure lead. These mines were worked

prior to, and long after, Agricola's time.

[27] This method of proportionate weights for assay charges is simpler

than the modern English "assay ton," both because of the use of 100

units in the standard of weight (the _centumpondium_), and because of

the lack of complication between the Avoirdupois and Troy scales. For

instance, an ore containing a _libra_ of silver to the _centumpondium_

would contain 1/100th part, and the same ratio would obtain, no matter

what the actual weight of a _centumpondium_ of the "lesser weight" might

be. To follow the matter still further, an _uncia_ being 1/1,200 of a

_centumpondium_, if the ore ran one "_uncia_ of the lesser weight" to

the "_centumpondium_ of the lesser weight," it would also run one actual

_uncia_ to the actual _centumpondium_; it being a matter of indifference

what might be the actual weight of the _centumpondium_ upon which the

scale of lesser weights is based. In fact Agricola's statement (p. 261)

indicates that it weighed an actual _drachma_. We have, in some places,

interpolated the expressions "lesser" and "greater" weights for clarity.

This is not the first mention of this scheme of lesser weights, as it

appears in the _Probierbuechlein_ (1500? see Appendix B) and Biringuccio

(1540). For a more complete discussion of weights and measures see

Appendix C. For convenience, we repeat here the Roman scale, although,

as will be seen in the Appendix, Agricola used the Latin terms in many

places merely as nomenclature equivalents of the old German scale.

Ozs.

dwts.

Troy gr.

Grains. per short ton.

1 _Siliqua_ 2.87 Per _Centumpondium_ 0 3 9

6 _Siliquae_ = 1 _Scripulum_ 17.2 " " 1 0 6

4 _Scripula_ = 1 _Sextula_ 68.7 " " 4 1 0

6 _Sextulae_ = 1 _Uncia_ 412.2 " " 24 6 2

12 _Unciae_ = 1 _Libra_ 4946.4 " " 291 13 8

100 _Librae_ = 1 _Centumpondium_ 494640.0

However Agricola may occasionally use

16 _Unciae_ = 1 _Libra_ 6592.0 (?)

100 _Librae_ = 1 _Centumpondium_ 659200.0 (?)

Also

Oz.

dwts.

gr.

per short ton.

1 _Scripulum_ 17.2 Per _Centumpondium_ 1 0 6

3 _Scripula_ = 1 _Drachma_ 51.5 " " 3 0 19

2 _Drachmae_ = 1 _Sicilicus_ 103.0 " " 6 1 15

4 _Sicilici_ = 1 _Uncia_ 412.2 " " 24 6 12

8 _Unciae_ = 1 _Bes_ 3297.6 " " 194 12 0

[28] The amalgamation of gold ores is fully discussed in note 12, p.

297.

[29] For discussion of the silver ores, see note 8, p. 108. _Rudis_

silver was a fairly pure silver mineral, the various coloured silvers

were partly horn-silver and partly alteration products.