According to M. Gay Lussac, 100 parts of water dissolve--_A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice

35·81 parts of the salt, at temperature 57·0° Fahr.

35·88 -- 62·5°

37·14 -- 140·0°

40·38 -- 229·5°

Native chloride of sodium, whether obtained from the waters of the

ocean, from saline lakes, from salt springs, or mineral masses, is never

perfectly pure. The foreign matters present in it vary with its

different origins and qualities. These are, the sulphates of lime,

magnesia, soda, muriates of magnesia and potash, bitumen, oxide of iron,

clay in a state of diffusion, &c.

Muriate of potash has been detected, in the waters of the ocean, in the

sal-gem of Berchtesgaden in Bavaria, of Hallein in the territory of

Salzbourg, and in the salt springs of Rosenheim.

The more heterogeneous the salt, the more soluble is it, by the

reciprocal affinity of its different saline constituents; and thus a

delicate hydrometer, plunged in saturated brine, may serve to show

approximately the quality of the salt. I find that the specific gravity

of a saturated solution of large-grained cubical salt, is 1·1962 at 60°

F. 100 parts of this brine contain 25-1/2 of salt, (100 w. + 34·2 s.)

From mutual penetration, 100 volumes of the aqueous and saline

constituents form rather less than 96 of the solution.

Among the varieties in the form of this salt, the octahedral, the

cubo-octahedral, and the dodecahedral, have been mentioned; but there is

another, called the funnel or hopper-shaped, which is very common. It is

a hollow rectangular pyramid, which forms at the surface of the saline

solution in the course of its evaporation, commencing with a small

floating cube, upon which lines of other little cubes attach themselves

to the edges of the upper face; whereby they form and enlarge the sides

of a hollow pyramid, whose apex, the single cubic crystal, is downward.

This sinks by degrees as the aggregation goes on above, till a pyramidal

boat of considerable size is constructed.

A TABLE of the results of the ANALYSES of several varieties of CULINARY

SALT.

+--------------------+-----+-----+-----+-----+-----+-----+-----+-----+

| |ride |ate |ate |phate|phate|phate|and |of |

| |of |of |of |of |of |of |other|Iron.|

| |Sodi-|Mag- |Lime.|Soda.|Mag- |Lime.|in- | |

| |um. |ne- | | |ne- | |solu-| |

| | |sia. | | |sia. | |ble | |

| | | | | | | |bod- | |

| | | | | | | |ies. | |

+--------------------+-----+-----+-----+-----+-----+-----+-----+-----+

|Sal-gem of Vic{white|99·30| -- | -- | -- | -- |0·005|0·020| |

| {red |99·80| -- | -- | -- | -- | -- |0·002| |

| crushed |98·33|0·02 | -- | -- | -- |0·65 | -- |0·002|

| | | | | | | | | |

|phalia |93·90|0·30 | -- |1·00 | -- |0·80 | | |

|Moutiers {des cordes|97·17|0·25 | -- |2·00 |0·58 | | | |

| {boilers |93·59|0·61 | -- |5·55 |0·25 | | | |

|Château Salins |97·82|2·12 | | | | | | |

|White of Sulz |96·88|3·12 | | | | | | |

|grained |99·45| -- | -- |0·05 | -- |0·28 | | |

|phalia |95·90| -- |0·27 | -- | -- |1·10 | | |

| | | | | | | | | |

|Sea salt, half white|97·20|0·004| -- | -- |0·050|0·120|0·070| |

|Malo |96· |0·30 | -- | -- |0·45 |2·35 | | |

|Common Scottish salt|93·55|2·80 | -- | -- |1·75 |1·50 | | |

|Lymington, common |93·7 | 1·1 | -- | -- |3·50 |1·50 |2·00 | |

|---------, cat |98·8 | 0·5 | -- | -- |0·5 |0·1 | | |

|Cheshire, stoved |98·25|0·075|0·025| -- | -- |1·55 | | |

+--------------------+-----+-----+-----+-----+-----+-----+-----+-----+

The geological position of rock salt is between the coal formation and

the lias. The great rock-salt formation of England occurs within the

_red marl_, or new red sandstone, the _bunter-sandstein_ of the Germans,

so called, because its colours vary from red to salmon and chocolate.

This mineral stratum frequently presents streaks of light blue,

verdigris, buff, or cream colour; and is chiefly remarkable for

containing considerable masses or beds of gypsum. At Northwich, in the

vale of the Weaver, the rock salt consists of two beds, together not

less than 60 feet thick, which are supposed to constitute large

insulated masses, about a mile and a half long, and nearly 1300 yards

broad. There are other deposits of rock salt in the same valley, but of

inferior importance. The uppermost bed occurs at 75 feet beneath the

surface, and is covered with many layers of indurated red, blue, and

brown clay, interstratified more or less with sulphate of lime, and

interspersed with argillaceous marl. The second bed of rock salt lies

31-1/2 feet below the first, being separated from it by layers of

indurated clay, with veins of rock salt running through them. The lowest

bed of salt was excavated to a depth of 110 feet, several years ago.

The beds or masses of rock salt are occasionally so thick, that they

have not been yet bored through, though mined for many centuries. This

is the case with the immense mass of Wieliczka, and the lower bed at

Northwich. But in ordinary cases, this thickness varies from an inch or

two to 12 or 15 yards. When the strata are thin, they are usually

numerous; but the beds, layers, or masses never exhibit throughout a

great extent any more than an illusory appearance of parallelism; for

when they are explored at several points, enlargements are observed, and

such diminutions as cause the salt to disappear sometimes altogether.

This mineral is not deposited, therefore, in a geological stratum, but

rather in lenticular masses, of very variable extent and thickness,

placed alongside of each other at unequal distances, and interposed

between the courses of the other formations.

Sometimes the rock salt is disseminated in small masses or little veins

among the calcareous and argillaceous marls which accompany or overlie

the greater deposits. Bitumen, in small particles, hardly visible, but

distinguishable by the smell, occurs in all the minerals of the

saliferous system.

It has been remarked, that the plants which grow generally on the sea

shores, such as the _Triglochinum maritimum_, the _Salicornia_, the

_Salsola kali_, the _Aster trifolium_, or farewell to summer, the _Glaux

maritima_, &c., occur also in the neighbourhood of salt mines and salt

springs, even of those which are most deeply buried beneath the surface.

The interior of rock-salt mines, after digging through the strata of

clay marl, &c. is extremely dry; so that the dust produced in the

workings becomes an annoyance to the miners, though in other respects

the excavations are not at all insalubrious.

Salt springs occur nearly in the same circumstances, and in the same

geological formation as the salt rock. It has been noticed that salt

springs issue, in general, from the upper portion of the saliferous

strata, principally from the saline clay marls. Cases however occur,

where the salt springs are not accompanied by rock salt, and where the

whole saline matter is derived from the marls themselves, which thus

constitute the only saliferous beds.

It has been imagined that there are two other periods of geological

formation of this substance; one much more antient, belonging to the

transition series of rocks; the other relatively modern, among secondary

strata. To the former has been referred the salt formation of Bex, that

of Cardonne, &c. But M. Brongniart assigns valid reasons for rejecting

this supposition. M. Beudant, indeed, refers to the secondary strata

above the chalk, the rock-salt formation of Wieliczka, and of the base

of the Carpathians; placing these among the plastic clay and lignites.

The mines of rock salt do not appear to possess any determinate

elevation upon the surface of the earth. Immense masses of it are met

with at very great depths below the level of the sea, (the mine of

Wieliczka is excavated 860 feet beneath the soil,) and others exist at a

considerable altitude, as that of Hallein near Salzbourg, which is 3300

feet above the level of the sea, and the saline rock of Arbonne in

Savoy, which is nearly 4000 feet higher, situated at the great elevation

of 7200 feet above the level of the sea, and consequently in the region

of perpetual snow. The rock is a mass of saccharoid and anhydrous

gypsum, imbued with common salt, which is extracted by lixiviation;

after which the gypsum remains porous and light.

The inland seas, salt lakes, and salt marshes, have their several

localities obviously independent of peculiar geological formations. The

ocean is, however, the most magnificent mine of salt, since this

chloride constitutes about one-thirtieth part of its weight; being

pretty evenly diffused throughout its waters, when no local cause

disturbs the equilibrium. The largest proportion of salt held in

solution in the open sea, is 38 parts in 1000, and the smallest 32. In a

specimen taken by Mr. Wilkinson, out of the Red Sea, at Berenice, I

found 43 parts of salt in 1000. The specific gravity of the water was

1·035.

Were it requisite to extract the chloride of sodium from sea-water by

fuel alone, many countries, even maritime, would find the process too

costly. The salt is therefore obtained from it in two different manners;

1. by natural evaporation alone; 2. by natural and artificial

evaporation combined. The first method is employed in warm regions,

under the form of saline tanks, or brine reservoirs, called also

brine-pits. These are large shallow basins, the bottom of which is very

smooth, and formed of clay. They are excavated along the sea-shore, and

consist of----

1st. A large reservoir, deeper than the proper brine-pits, which is dug

between them and the sea. This reservoir communicates with the sea by

means of a channel provided with a sluice. On the sea-shore, these

reservoirs may be filled at high water, though the tides are rather

inconvenient than advantageous to brine-pits.

2dly. The brine-pits, properly so called, which are divided into a

number of compartments by means of little banks. All these compartments

have a communication with each other, but so that the water frequently

has a long circuit to make, from one set to another. Sometimes it must

flow 400 or 500 yards, before it reaches the extremity of this sort of

labyrinth. The various divisions have a number of singular names, by

which they are technically distinguished. They should be exposed to the

north, north-east, or north-west winds.

The water of the sea is let into these reservoirs in the month of March,

where it is exposed on a vast surface to evaporation. The first

reservoir is intended to detain the water till its impurities have

subsided, and from it the other reservoirs are supplied, as their water

evaporates. The salt is considered to be on the point of crystallizing

when the water begins to grow red. Soon after this, a pellicle forms on

the surface, which breaks, and falls to the bottom. Sometimes the salt

is allowed to subside in the first compartment; at others, the strong

brine is made to pass on to the others, where a larger surface is

exposed to the air. In either case the salt is drawn out, and left upon

the borders to drain and dry.

The salt thus obtained, partakes or the colour of the bottom on which it

is formed; and is hence white, red, or gray.

Sea water contains, in 1000 parts, 25 of chloride of sodium, 5·3

sulphate of magnesia, 3·5 chloride of magnesium, 0·2 carbonate of lime

and magnesia, 0·1 sulphate of lime, besides 1/2000 of sulphate and

muriate of potash. It also contains iodide of sodium, and bromide of

magnesium. Its average spec. grav. is from 1·029 to 1·030.

[Illustration: 962 963 964]

Sea-water and weak brines may be concentrated either by the addition of

rock salt, by spontaneous evaporation in brine-pits (see _suprà_), or by

graduation. Houses for the last purpose are extensively employed in

France and Germany. The weak brine is pumped into an immense cistern on

the top of a tower, and is thence allowed to flow down the surface of

bundles of thorns built up in regular walls, between parallel wooden

frames. At Salza, near Schönebeck, the graduation-house is 5817 feet

long, the thorn walls are from 33 to 52 feet high, in different parts,

and present a total surface of 25,000 square feet. Under the thorns, a

great brine cistern, made of strong wooden planks, is placed, to receive

the perpetual shower of water. Upon the ridge of the graduation-house

there is a long spout, perforated on each side with numerous holes, and

furnished with spigots or stopcocks for distributing the brine, either

over the surface of the thorns, or down through their mass; the latter

method affording larger evaporation. The graduation-house should be

built lengthwise in the direction of the prevailing wind, with its ends

open. An experience of many years at Salza and Dürrenberg has shown,

that in the former place graduation can go on 258, and in the latter 207

days, on an average, in the year; the best season being from May till

August. At Dürrenberg, 3,596,561 cubic feet of water are evaporated

annually. According to the weakness of the brine, it must be the more

frequently pumped up, and made to flow down over the thorns in different

compartments of the building, called the 1st, 2d, and 3d graduation. A

deposit of gypsum incrusts the twigs, which requires them to be renewed

at the end of a certain time. _Figs._ 962. and 963. represent the

graduation-house of the salt-works at Dürrenberg. _a_, _a_, _a_, are low

stone pillars for supporting the brine cistern _b_, called the

_soole-schiff_. _c_, _c_ are the inner, _d_, _d_ the outer, walls of

thorns; the first have perpendicular sides, the last sloping. The spars

_e_, _e_, which support the thorns, are longer than the interval between

two thorn walls from _f_ to _g_, _fig._ 963, whereby they are readily

fastened by their tenons and mortises. The spars are laid at a slope of

2 inches in the foot, as shown by the line _h_, _i_. The bundles of

thorns are each 1-1/2 foot thick, from 5 to 7 feet long, and are piled

up in the following way:----Guide-bars are first placed in the line _k_,

_l_, to define the outer surface of the thorn wall, the undermost spars

_m_, _n_, are fastened upon them; and the thorns are evenly spread,

after the willow-withs of the bundles have been cut. Over the top of the

thorn walls are laid, through the whole length of the graduation-house,

the brine spouts _o_, _o_, which are secured to the upper beams; and at

both sides of these spouts are the drop-spouts _p_, _p_, for discharging

the brine by the spigots _s_, _s_, as shown upon a larger scale in

_fig._ 964. The drop-spouts are 6 feet long, have on each side small

notches, 5 inches apart, and are each supplied by a spigot. The space

above the ridge of the graduation-house is covered with boards,

supported at their ends by binding-beams _q_. _r_, _r_ show the tenons

of the thorn-spars. Over the soole schiff _b_, inclined planes of boards

are laid for conducting downwards the innumerable showers. The brine,

which contains at first 7·692 per cent. of salt, indicates, after the

first shower, 11·473; after the second, 16·108; and after the third, 22.

The brine, thus concentrated to such a degree as to be fit for boiling,

is kept in great reservoirs, of which the eight at Salza, near

Schönebeck, have a capacity of 2,421,720 cubic feet, and are furnished

with pipes leading to the sheet-iron salt-pans. The capacity of these is

very different at different works. At Schönebeck there are 22, the

smallest having a square surface of 400 feet, the largest of 1250, and

are enclosed within walls, to prevent their being affected by the cold

external air. They are covered with a funnel-formed or pyramidal trunk

of deals, ending in a square chimney, to carry off the steam.

[Illustration: 965 966 967]

_Figs._ 965, 966, 967. represent the construction of a salt-pan, its

furnace, and the salt store-room of the works at Dürrenberg; _fig._ 967.

being the ground plan, _fig._ 966. the longitudinal section, and _fig._

965. the transverse section, _a_ is the fire-grate, which slopes upwards

to the back part, and is 31-1/2 inches distant from the bottom of the

pan. The ratio of the surface of the grate to that of the bottom of the

pan, is as 1 to 59·5; that of the air-hole into the ash-pit, as 1 to

306. The bed under the pan is laid with bricks, smoothly plastered over,

from _b_ to _c_, in _fig._ 966. Upon this bed the pillars _d_, _d_, &c.,

are built in a radiated direction, being 6 inches broad at the bottom,

and tapering to 1-1/2 inch at top. The pan is so laid that its bottom

has a fall towards the middle of 2-1/2 inches: see _e_, _f_, _fig._ 966.

The fire diffuses itself in all directions under the pan, proceeds

thence through several holes _g_, _g_, _g_, into flues _h_, _h_, _h_,

which run round three sides of the pan; the burnt air then passes

through _i_, _fig._ 967., under other pans, from which it is collected

in the chimneys _k_, _k_, to be conducted into the drying-room. At _l_,

_l_, there is a transverse flue, through which, by means of dampers, the

fire-draught may be conducted into an extra chimney _m_. From the flues

_k_, _k_, four square iron pipes _n_, _n_, issue and conduct the burnt

air into the main chimneys in the opposite wall.

The bottoms of the several flues have a gradual ascent above the level

of the fire-grate. A special chimney _o_, rises above the ash-pit, to

carry off the smoke, which may chance to regurgitate in certain states

of the wind. _p_, _p_, are iron pipes laid upon each side of the ash-pit

(see _figs._ 966. and 967.), into which cold air is admitted by the flue

_q_, _r_, where, becoming heated, it is conducted through iron pipes

_s_, and thence escapes at _t_, into the stove-room. Upon both sides of

the hot flues in the stove-room, hurdle-frames _u_, _u_, are laid, each

of which contains 11 baskets, and every basket, except the undermost,

holds 60 pounds of salt, spread in a layer 2 inches thick. _v_, _v_,

show the pipes by which the pan is supplied with graduated brine.

_Description of the Steam-trunk, in fig. 968._

[Illustration: 968]

In front of the pan _a_, _a_, there are two upright posts, upon which,

and in holes of the back wall, two horizontal beams _b_, _b_, are

supported. The pillars _c_, _c_, are sustained upon the bearers _d_,

_d_. At _e_, _e_, a deep quadrangular groove is made in the beams, for

fixing down the four boards which form the bottom of the steam-way. In

this groove any condensed water from the steam collects, and is carried

off by a pipe _f_, to prevent it falling back into the pan. Upon the

three sides of the pan not in contact with the wall, there are three

rows of boards hinged upon planks _b_, _b_. Behind the upper one, a

board is hung on at _g_, upon which the boiled salt is laid to drain.

The two other rows of boards are hooked on so as to cover the pan, as

shown at _h_. Whenever the salt is sufficiently drained, the upper

shelves are placed in a horizontal position; the salt is put into small

baskets, and carried into the stove-room. _i_, _k_, is the steam-trunk;

_l_, _m_, is a tunnel for carrying off the steam from the middle of the

pan, when this is uncovered by lifting the boards.

In proportion as the brine becomes concentrated by evaporation, more is

added from the settling reservoir of the graduation-house, till finally

small crystals appear on the surface. No more weak brine is now added,

but the charge is worked off, care being taken to remove the scum, as it

appears. In some places the first pan is called a schlot-pan, in which

the concentration is carried only so far as to cause the deposition of

the sludge, from which the saline solution is run into another pan, and

gently evaporated, to produce the precipitation of the fine salt. This

salt should be continually raked towards the cooler and more elevated

sides of the pan, and then lifted out with cullender-shovels into large

conical baskets, arranged in wooden frames round the border of the pan,

so that the drainage may flow back into the boiling liquor. The drained

salt is transferred to the hurdles or baskets in the stove-room, which

ought to be kept at a temperature of from 120° to 130°, Fahr. The salt

is then stowed away in the warehouse.

The graduation range should be divided lengthwise into several sections:

the first to receive the water of the spring, the lake, or the sea; the

second, the water from the first shower-receiver; the third, the water

from the second receiver; and so on. The pumps are usually placed in the

middle of the building, and lift the brine from the several receivers

below into the alternate elevated cisterns. The square wooden spouts of

distribution may be conveniently furnished with a slide-board, attached

to each of their sides, to serve as a general valve for opening or

shutting many trickling orifices at once. The rate of evaporation at

Moutiers is exhibited by the following table:----

+-----------------------+----------------+----------------+-------+

+-----------------------+----------------+----------------+-------+

| | | 1·010 | 0·000 |

|1 and 2 |5158 square feet| 1·023 | 0·540 |

|3, 4, 5, 6, 7, 8, and 9|2720 | 1·072 | 0·333 |

|10 | 550 | 1·140 | 0·062 |

| ----- |

| Total evaporation 0·935 |

| Water remaining in the brine at the density of 1·140 1·065 |

| ----- |

| Water assigned at the density of 1·010 1·000 |

+-----------------------------------------------------------------+

From the above table it appears that no less than 10 falls of the brine

have been required to bring the water from the specific gravity 1·010 to

1·140, or 18° Baumé. The evaporation is found to proceed at nearly the

same rate with the weaker water, and with the stronger, within the above

limits. When it arrives at a density of from 1·140 to 1·16, it is run

off into the settling cisterns. M. Berthier calculates, that upon an

average, in ordinary weather, at Moutiers, 60 kilogrammes of water (13

gallons, imp.) are evaporated from the fagots, in the course of 24

hours, for every square foot of their surface. Without the aid of

currents of air artificially warmed, such an amount of evaporation could

not be reckoned upon in this country. In the _schlotting_, or throwing

down of the sediment, a little bullock’s blood, previously beaten up

with some cold brine, promotes the clarification. When the brine

acquires, by brisk ebullition, the density of 1·200, it should be run

off from the preparation, to the finishing or salting pans.

The mother-water contains a great deal of chloride of magnesium, along

with chloride of sodium, and sulphate of magnesia. Since the last two

salts mutually decompose each other at a low temperature, and are

transformed into sulphate of soda, which crystallizes, and muriate of

magnesia, which remains dissolved, the mother-water with this view may

be exposed in tanks to the frost during winter, when it affords three

successive crystalline deposits, the last being sulphate of soda, nearly

pure.

The chloride of magnesium, or bittern, not only deteriorates the salt

very much, but occasions a considerable loss of weight. It may, however,

be most advantageously got rid of, and converted into chloride of sodium

by the following simple expedient:----Let quicklime be introduced in

equivalent quantity to the magnesia present, and it will precipitate

this earth, and form chloride of calcium, which will immediately react

upon the sulphate of soda in the mother-water, with the production of

sulphate of lime and chloride of sodium. The former being sparingly

soluble, is easily separated. Lime, moreover, decomposes directly the

chloride of magnesium, but with the effect of merely substituting

chloride of calcium in its stead. But in general there is abundance of

sulphate of soda in brine springs to decompose the chloride of calcium.

A still better way of proceeding with sea-water, would be to add to it,

in the settling tank, the quantity of lime equivalent to the magnesia,

whereby an available deposit of this earth would be obtained, at the

same time that the brine would be sweetened. Water thus purified may be

safely crystallized by rapid evaporation.

In summer, the saturated boiling brine is crystallized by passing it

over vertical ropes; for which purpose 100,000 metres (110,000 yards)

are mounted in an apartment 70 metres (77 yards) long. When the salt has

formed a crust upon the ropes about 2-1/2 inches thick, it is broken

off, allowed to fall upon the clean floor of the apartment, and then

gathered up. The salting of a charge, which would take 5 or 6 days in

the pan, is completed in this way in 17 hours; but the mother-waters are

more abundant. The salt is, however, remarkably pure.

The boilers constructed at Rosenheim, in Bavaria, evaporate 3-1/2 pounds

of water for every pound of wood burned; which is reckoned a favourable

result; but some of those described under EVAPORATION, would throw off

much more.

“The rock salt mines and principal brine springs are in Cheshire; and

the chief part of the Cheshire salt, both fossil and manufactured, is

sent by the river Weaver to Liverpool, a very small proportion of it

being conveyed elsewhere, by canal or land carriage. There are brine

springs in Staffordshire, from which Hull is furnished with white salt;

and in Worcestershire, from which Gloucester is supplied. If to the

quantity shipped by the Weaver, 100,000 tons of white salt are added

annually for internal consumption and exports, exclusive of Liverpool,

the total manufacture will be approached very nearly; but as there is

now no check from the excise, it is impossible to ascertain it exactly.

Fossil salt is used in small quantities at some of the Cheshire

manufactories, to strengthen the brine, but is principally exported;

some to Ireland, but chiefly to Belgium and Holland.”[52] The average

quantity of rock salt sent annually down the river Weaver, from the

mines in Cheshire, between the years 1803 and 1834 inclusive, was 86,000

tons, of 2,600 lbs. each; the greatest being 125,658, in the year 1823,

and the least 47,230, in the year 1813. The average quantity of white

salt sent annually down the Weaver from the manufactories in Cheshire

during the same period, was 221,351; the greatest being 383,669, in the

year 1832, and the least being 120,486, in the year 1811.

[52] Tables of the Revenue, Population, Commerce, &c., for 1836, p.

122.

M. Clement-Desormes, engineer and chief _actionnaire_ of the great

salt-works of Dieuze, in France, informs me that the internal

consumption of that kingdom is rather more than 200,000 tons per annum,

being at the rate of 6-1/2 kilogrammes for each individual of a

population estimated at 32,000,000. As the retail price of salt in

France is 10 sous per kilogramme (of 2-1/5 lbs. avoird.), while in this

country it is not more than 2 sous (1 penny), its consumption per head

will be much greater with us; and, taking into account the immense

quantity of salted provisions that are used, it may be reckoned at 22

lbs.; whence our internal consumption will be 240,000 tons, instead of

100,000, as quoted above, from the tables published by the Board of

Trade.

In 1836, 9,622,427 bushels, of 56 lbs. = 240,560 tons of salt, value

173,923_l._, were exported from the United Kingdom, of which 1,350,849

bushels went to Russia; 1,235,086 to Belgium; 314,132 to the Western

coast of Africa; 1,293,560 to the British North American colonies;

2,870,808 to the United States of America; 53,299 to New South Wales,

Van Diemen’s Land, and other Australian settlements; 58,735 to the

British West Indies; and 90,655 to Guernsey, Jersey, Alderney, and Man.

SAND (Eng. and Germ.; _Sable_, Fr.); is the name given to any mineral

substance in a hard granular or pulverulent form, whether strewed upon

the surface of the ground, found in strata at a certain depth, forming

the beds of rivers, or the shores of the sea. The siliceous sands seem

to be either original crystalline formations, like the sand of Neuilly,

in 6-sided prisms, terminated by two 6-sided pyramids, or the _débris_

of granitic, schistose, quartzose, or other primitive crystalline rocks,

and are abundantly distributed over the globe; as in the immense plains

known under the names of downs, deserts, _steppes_, _landes_, &c.,

which, in Africa, Asia, Europe, and America, are entirely covered with

loose sterile sand. Valuable metallic ores, those of gold, platinum,

tin, copper, iron, titanium, often occur in the form of sand, or mixed

with that earthy substance. Pure siliceous sands are very valuable for

the manufacture of glass, for making mortars, filters, ameliorating

dense clay soils, and many other purposes. For moulder’s sand, see

FOUNDING. Lynn and Ryegate furnish our purest siliceous sand.

SANDAL or RED SAUNDERS WOOD (_Santal_ Fr.; _Sandelholz_ Germ.); is the

wood of the _Pterocarpus santalinus_, a tree which grows in Ceylon, and

on the coast of Coromandel. The old wood is preferred by dyers. Its

colouring matter is of a resinous nature; and is, therefore, quite

soluble in alcohol, essential oils, and alkaline lyes; but sparingly in

boiling water, and hardly if at all in cold water. The colouring matter

which is obtained by evaporating the alcoholic infusion to dryness, has

been called _santaline_; it is a red resin, which is fusible at 212° F.

It may also be obtained by digesting the rasped sandal wood in water of

ammonia, and afterwards saturating the ammonia with an acid. The

_santaline_ falls, and the supernatant liquor, which is yellow by

transmitted, appears blue by reflected light. Its spirituous solution

affords a fine purple precipitate with the protochloride of tin, and a

violet one with the salts of lead. Santaline is very soluble in acetic

acid, and the solution forms permanent stains upon the skin.

Sandal wood is used in India, along with one-tenth of _sapan_ wood (the

_Cæsalpinia sapan_ of Japan, Java, Siam, Celebes, and the Philippine

isles), principally for dyeing silk and cotton. Trommsdorf dyed wool,

cotton, and linen a carmine hue by dipping them alternately in alkaline

solution of the sandal wood, and in an acidulous bath. Bancroft obtained

a fast and brilliant reddish-yellow, by preparing wool with an alum and

tartar bath, and then passing it through a boiling bath of sandal wood

and sumac. Pelletier did not succeed in repeating this experiment.

According to Togler, wool, silk, cotton, and linen, mordanted with salt

of tin, and dipped in a cold alcoholic tincture of the wood, or the same

tincture mixed with 8 parts of boiling water, become of a superb

ponceau-red colour. With alum, they took a scarlet-red; with sulphate of

iron, a deep violet, or brown-red. Unluckily these dyes do not stand

exposure to light well.

SANDARACH, is a peculiar resinous substance, the product of the _Thuya

articulata_, a small tree of the coniferous family, which grows in the

northern parts of Africa, especially round Mount Atlas.

The resin comes to us in pale yellow, transparent, brittle, small tears,

of a spherical or cylindrical shape. It has a faint aromatic smell, does

not soften, but breaks between the teeth, fuses readily with heat, and

has a specific gravity of from 1·05 to 1·09. It contains three different

resins; one soluble in spirit of wine, somewhat resembling _pinic acid_

(see TURPENTINE); one not soluble in that menstruum; and a third,

soluble only in alcohol of 90 per cent. It is used as pounce-powder for

strewing over paper erasures, as incense, and in varnishes.

SAPAN WOOD, is a species of the _Cæsalpinia_ genus, to which Brasil wood

belongs. It is so called by the French, because it comes to them from

Japan, which they corruptly pronounce Sapan. As all the species of this

tree are natives of either the East Indies or the New World, one would

imagine that they could not have been used as dye-stuffs in Europe

before the beginning of the 16th century. Yet the author of the article

“Brasil,” in Rees’ Cyclopædia, and Mr. Southey, in his History of

Brasil, say that _Brasil_ wood is mentioned nearly one hundred years

before the discoveries of Columbus and Vasco de Gama, by Chaucer, who

died in 1400; that it was known many ages before his time; and that it

gave the name to the country, instead of the country giving the name to

the wood, as I have stated, with Berthollet and other writers on dyeing.

The _Cæsalpinia sappan_, being a native of the Coromandel coast, may

_possibly_ have been transported along with other Malabar merchandise to

the Mediterranean marts in the middle ages; but the importation of so

lumbering an article in any considerable quantity by that channel, is so

improbable, that I am disposed to believe that Brasil wood was not

commonly used by the dyers of Europe before the discovery of the New

World.

SARD; see LAPIDARY.

SATIN (Eng., Fr., and Germ.); is the name of a silk stuff, first

imported from China, which is distinguished by its very smooth,

polished, and glossy surface. It is woven upon a loom with at least

five-leaved healds or heddles, and as many corresponding treddles. These

are so mounted as to rise and fall four at a time, raising and

depressing alternately four yarns of the warp, across the whole of which

the weft is thrown by the shuttle, so as to produce a uniform smooth

texture, instead of the chequered work resulting from intermediate

decussations, as in common webs. See TEXTILE FABRICS. Satins are woven

with the glossy or right side undermost, because the four-fifths of the

warp, which are always left there during the action of the healds, serve

to support the shuttle in its race. Were they woven in the reverse way,

the scanty fifth part of the warp threads could either not support, or

would be too much worn by the shuttle.

SATURATION, is the term at which any body has taken its full dose or

chemical proportion of any other with which it can combine; as water

with a salt, or an acid with an alkali in the neutro-saline state.

SCALIOLA, is merely ornamental plaster-work, produced by applying a pap

made of finely-ground calcined gypsum, mixed with a weak solution of

Flanders’ glue, upon any figure formed of laths nailed together, or

occasionally upon brickwork, and bestudding its surface, while soft,

with splinters (_scagliole_) of spar, marble, granite, bits of concrete,

coloured gypsum, or veins of clay, in a semi-fluid state. The substances

employed to colour the spots and patches, are the several ochres, boles,

_terra di Sienna_, chrome yellow, &c. The surface of the column is

turned smooth upon a lathe, polished with stones of different fineness,

and finished with some plaster-pap, to give it lustre. Pillars and other

flat surfaces are smoothed by a carpenter’s plane, with the chisel

finely serrated, and afterwards polished with plaster by friction. The

glue is the cause of the gloss, but makes the surface apt to be injured

by moisture, or even damp air.

SCARLET DYE. (_Teinture en écarlate_, Fr.; _Scharlachfärberei_, Germ.)

Scarlet is usually given at two successive operations. The boiler (see

_figs._ 364, 365., article DYEING,) is made of block tin, but its bottom

is formed occasionally of copper.

1. _The bouillon, or the colouring-bath._--For 100 pounds of cloth, put

into the water, when it is little more than lukewarm, 6 pounds of argal,

and stir it well. When the water becomes too hot for the hand, throw

into it, with agitation, one pound of cochineal in fine powder. An

instant afterwards, pour in 5 pounds of the clear mordant G, (see TIN

MORDANTS,) stir the whole thoroughly as soon as the bath begins to boil,

introduce the cloth, and wince it briskly for two or three rotations,

and then more slowly. At the end of a two-hours’ boil, the cloth is to

be taken out, allowed to become perfectly cool, and well washed at the

river, or winced in a current of pure water. (See an automatic plan of

washing described under the article RINSING MACHINE.)

2. _The rougie, or finishing dye._--The bouillon bath is emptied, and

replaced with water for the _rougie_. When it is on the point of

boiling, 5-1/2 pounds of cochineal in fine powder are to be thrown in,

and mixed with care; when the crust, which forms upon the surface, opens

of itself in several places, 14 pounds of solution of tin (as above) are

to be added. Should the liquor be likely to boil over the edges of the

kettle, it must be refreshed with a little cold water. When the bath has

become uniform, the cloth is to be put in, taking care to wince it

briskly for two or three turns; then to boil it bodily for an hour,

thrusting it under the liquor with a rod whenever it rises to the

surface. It is lastly taken out, aired, washed at the river, and dried.

As no person has done more for the improvement of the scarlet dyes than

Poërner, I shall here give his processes in detail.

_Bouillon, or colouring._--For every pound of cloth or wool, take 14

drams of cream of tartar. When the bath is boiling, and the tartar all

dissolved, pour in successively 14 drams of solution of tin, (_Mordant_

F, TIN,) and let the whole boil together during a few minutes. Now

introduce the cloth, and boil it for 2 hours; then take it out, and let

it drain and cool.

_Rougie, or dye._--For every pound of woollen stuff, take 2 drams of

cream of tartar. When the bath begins to boil, add 1 ounce of cochineal

reduced to fine powder, stir the mixture well with a rod of willow or

any white wood, and let it boil for a few minutes. Then pour in, by

successive portions, 1 ounce of solution of tin (_Mordant_ F), stirring

continually with the rod. Lastly, dye as quickly as possible. The colour

will be a beautiful scarlet.

_Second scarlet process of Poërner_, the _bouillon_ being the same as

above given, and always estimated for 1 pound of cloth or wool.

_Rougie._--Take one ounce of cochineal in fine powder, and two ounces of

solution of tin without tartar.

_Third scarlet process of Poërner_; the _bouillon_ being as above.

_Rougie_ for a pound of cloth.--Take two drams of cream of tartar, one

ounce of cochineal, one ounce of solution of tin, and two ounces of sea

salt: dye as in process 1. The salt helps the dye to penetrate into the

cloth.

TABLES of the COMPOSITION of the BOUILLON and ROUGIE, by different

Authors, for 100 pounds of Cloth or Wool.

_Composition of the Bouillon._

+------------+----------+----------+----------+----------+---------+

+------------+----------+----------+----------+----------+---------+

| | | | | | |

|Berthollet | 0 0 | 6 0 | 8 0 | 5 0 | 0 0 |

|Hellot | 0 0 | 12 8 | 18 6 | 12 8 | 0 0 |

|Scheffer | 9 6 | 9 6 | 12 4 | 9 6 | 0 0 |

|Poërner | 0 0 | 10 15 | 0 0 | 10 15 | 0 0 |

+------------+----------+----------+----------+----------+---------+

_Composition of the Rougie_.

+------------+----------+----------+-----------+---------+---------+

+------------+----------+----------+-----------+---------+---------+

|Berthollet | 0 0 | 0 0 | 5 8 | 14 0 | 0 0 |

|Hellot | 3 2 | 0 0 | 7 4 | 12 8 | 0 0 |

|Scheffer | 3 2 | 3 2 | 5 7-1/2| 4 11 | 0 0 |

| {| 0 0 | 1 8 | 6 4 | 6 4 | 0 0 |

|Poërner {| 0 0 | 0 0 | 6 4 | 12 8 | 0 0 |

| {| 0 0 | 1 8 | 6 4 | 6 4 | 12 8 |

+------------+----------+----------+-----------+---------+---------+

M. Lenormand states that he has made experiments of verification upon

all the formulæ of the preceding tables, and declares his conviction

that the finest tint may be obtained by taking the _bouillon_ of

Scheffer, and the _rougie_ No. 4. of Poërner. The solution which

produced the most brilliant red, is that made according to the process

of mordant B (TIN). M. Robiquet has given the following prescription for

making a _printing scarlet_, for well-whitened woollen cloth.

Boil a pound of pulverized cochineal in four pints of water down to two

pints, and pass the decoction through a sieve. Repeat the boiling three

times upon the residuum, mix the eight pints of decoction, thicken them

properly with two pounds of starch, and boil into a paste. Let it cool

down to 104° F., then add four ounces of the subjoined solution of tin,

and two ounces of ordinary salt of tin (muriate). When a ponçeau red is

wanted, two ounces of pounded curcuma (turmeric) should be added.

The solution of tin above prescribed, is made by taking--one ounce of

nitric acid, of specific gravity 36° B. = 1·33; one ounce of sal

ammoniac; four ounces of grain tin. The tin is to be divided into eight

portions, and one of them is to be put into the acid mixture every

quarter of an hour.

A solution of chlorate of potassa (chloride?) is said to beautify

scarlet cloth in a remarkable manner.

Bancroft proposed to supplant the nitro-muriatic acid, by a mixture of

sulphuric and muriatic acids, for dissolving tin; but I do not find that

he succeeded in persuading scarlet-dyers to adopt his plans. In fact the

proper base is, in my opinion, a mixture of the protoxide and peroxide

of tin; and this cannot be obtained by acting upon the metal with the

murio-sulphuric acid. He also prescribed the extensive use of the

quercitron yellow to change the natural crimson of the cochineal into

scarlet, thereby economizing the quantity of this expensive dye-stuff.

See LAC DYE.

SCHEELE’S GREEN, is a pulverulent arsenite of copper, which may be

prepared as follows:--Form, first, an arsenite of potassa, by adding

gradually 11 ounces of arsenious acid to 2 pounds of carbonate of

potassa, dissolved in 10 pounds of boiling water; next, dissolve 2

pounds of crystallized sulphate of copper in 30 pounds of water; filter

each solution, then pour the first progressively into the second, as

long as it produces a rich grass-green precipitate. This being thrown

upon a filter-cloth, and edulcorated with warm water, will afford 1

pound 6 ounces of this beautiful pigment. It consists of, oxide of

copper 28·51, and of arsenious acid 71·46. This green is applied by an

analogous double decomposition to cloth. See CALICO-PRINTING.

SCHWEINFURTH GREEN, is a more beautiful and velvety pigment than the

preceding, which was discovered in 1814, by MM. Rusz and Sattler, at

Schweinfurth, and remained for many years a profitable secret in their

hands. M. Liebig having made its composition known, in 1822, it has been

since prepared in a great many colour-works. Braconnot published, about

the same time, another process for manufacturing the same pigment. Its

preparation is very simple; but its formation is accompanied with some

interesting circumstances. On mixing equal parts of acetate of copper

and arsenious acid, each in a boiling concentrated solution, a bulky

olive-green precipitate is immediately produced; while much acetic acid

is set free. The powder thus obtained, appears to be a compound of

arsenious acid and oxide of copper, in a peculiar state; since when

decomposed by sulphuric acid, no acetic odour is exhaled. Its colour is

not changed by drying, by exposure to air, or by being heated in water.

But, if it be boiled in the acidulous liquor from which it was

precipitated, it soon changes its colour, as well as its state of

aggregation, and forms a new deposit in the form of a dense granular

beautiful green powder. As fine a colour is produced by ebullition

during five or six minutes, as is obtained at the end of several hours

by mixing the two boiling solutions, and allowing the whole to cool

together. In the latter case, the precipitate, which is slight and

flocky at first, becomes denser by degrees; it next betrays green spots,

which progressively increase, till the mass grows altogether of a

crystalline constitution, and of a still more beautiful tint than if

formed by ebullition.

When cold water is added to the mixed solutions, immediately after the

precipitate takes place, the development of the colour is retarded,

with the effect of making it much finer. The best mode of procedure, is

to add to the blended solutions, their own bulk of cold water, and to

fill a globe up to the neck with the mixture in order to prevent the

formation of any such pellicle on the surface, as might, by falling to

the bottom, excite premature crystallization. Thus the reaction

continues during two or three days with the happiest effect. The

difference of tint produced by these variations, arises merely from the

different sizes of the crystalline particles; for when the several

powders are levigated upon a porphyry slab to the same degree, they have

the same shade. Schweinfurth green, according to M. Ehrmann’s

researches, in the 31st _Bulletin de la Société Industrielle de

Mulhausen_, consists of, oxide of copper 31·666, arsenious acid 58·699,

acetic acid 10·294. Kastner has given the following prescription for

making this pigment:--For 8 parts of arsenious acid, take from 9 to 10

of verdigris; diffuse the latter through water at 120° F., and pass the

pap through a sieve; then mix it with the arsenical solution, and set

the mixture aside, till the reaction of the ingredients shall produce

the wished-for shade of colour. If a yellowish tint be desired, more

arsenic must be used. By digesting Scheele’s green in acetic acid, a

variety of Schweinfurth green may be obtained.

Both of the above colours are rank poisons. The first was detected a few

years ago, as the colouring-matter of some Parisian _bonbons_, by the

_conseil de salubrité_; since which the confectioners were prohibited

from using it, by the French government.

SCOURING, _or renovating articles of dress_. This art has been much more

studied by Frenchmen, who wear the same coats for two or three years,

than by Englishmen, who generally cast them off after so many months.

The workmen who remove greasy stains from dress, are called, in France,

_teinturiers-degraisseurs_, because they are often obliged to combine

dyeing with scouring operations. The art of cleansing clothes being

founded upon the knowledge of solvents, the practitioner of it should,

as we shall presently illustrate by examples, be acquainted with the

laws of chemical affinity.

Among the spots which alter the colours fixed upon stuffs, some are

caused by a substance which may be described as _simple_, in common

language; and others by a substance which results from the combination

of two or more bodies, that may act separately or together upon the

stuff, and which may therefore be called _compound_.

_Simple stains._--Oils and fats are the substances which form the

greater part of simple stains. They give a deep shade to the ground of

the cloth; they continue to spread for several days; they attract the

dust, and retain it so strongly, that it is not removable by the brush;

and they eventually render the stain lighter coloured upon a dark

ground, and of a disagreeable gray tint upon a pale or light ground.

The general principle of cleansing all spots, consists in applying to

them a substance which shall have a stronger affinity for the matter

composing them, than this has for the cloth, and which shall render them

soluble in some liquid menstruum, such as water, spirits, naphtha, oil

of turpentine, &c. See BLEACHING.

Alkalis would seem to be proper in this point of view, as they are the

most powerful solvents of grease; but they act too strongly upon silk

and wool, as well as change too powerfully the colours of dyed stuffs,

to be safely applicable in removing stains. The best substances for this

purpose are--1. Soap. 2. Chalk, fuller’s earth, soap-stone or steatite

(called in this country French chalk). These should be merely diffused

through a little water into a thin paste, spread upon the stain, and

allowed to dry. The spot requires now to be merely brushed. 3. Ox-gall

and yolk of egg have the property of dissolving fatty bodies without

affecting perceptibly the texture or colours of cloth, and may therefore

be employed with advantage. The ox-gall should be purified, to prevent

its greenish tint from degrading the brilliancy of dyed stuffs, or the

purity of whites. Thus prepared (see GALL), it is the most precious of

all substances known for removing these kinds of stains. 4. The volatile

oil of turpentine will take out only recent stains; for which purpose it

ought to be previously purified by distillation over quicklime. Wax,

rosin, turpentine, pitch, and all resinous bodies in general, form

stains of greater or less adhesion, which may be dissolved out by pure

alcohol. The juices of fruits, and the coloured juices of all vegetables

in general, deposit upon clothes marks in their peculiar hues. Stains of

wine, mulberries, black currants, morellos, liquors, and weld, yield

only to soaping with the hand, followed by fumigation with sulphurous

acid; but the latter process is inadmissible with certain coloured

stuffs. Iron mould or rust stains may be taken out almost

instantaneously with a strong solution of oxalic acid. If the stain is

recent, cream of tartar will remove it.

_Compound spots._--That mixture of rust of iron and grease called

_cambouis_ by the French, is an example of this kind, and requires two

distinct operations; first, the removal of the grease, and then of the

rust, by the means above indicated.

Mud, especially that of cities, is a compound of vegetable remains, and

of ferruginous matter in a state of black oxide. Washing with pure

water, followed if necessary with soaping, will take away the vegetable

juices; and then the iron may be removed with cream of tartar, which

itself must, however, be well washed out. Ink stains, when recent, may

be taken out by washing, first with pure water, next with soapy water,

and lastly with lemon juice; but if old, they must be treated with

oxalic acid. Stains occasioned by smoke, or by sauces browned in a

frying-pan, may be supposed to consist of a mixture of pitch, black

oxide of iron, empyreumatic oil, and some saline matters dissolved in

pyrolignous acid. In this case several reagents must be employed to

remove the stains. Water and soap dissolve perfectly well the vegetable

matters, the salts, the pyrolignous acid, and even the empyreumatic oils

in a great measure; the essence of turpentine will remove the rest of

the oils and all the pitchy matter; then oxalic acid may be used to

discharge the iron. Coffee stains require a washing with water, with a

careful soaping, at the temperature of 120° F., followed by

sulphuration. The two latter processes may be repeated twice or thrice.

Chocolate stains may be removed by the same means, and more easily.

As to those stains which change the colour of the stuff, they must be

corrected by appropriate chemical reagents or dyes. When black or brown

cloth is reddened by an acid, the stain is best counteracted by the

application of water of ammonia. If delicate silk colours are injured by

soapy or alkaline matters, the stains must be treated with colourless

vinegar of moderate force. An earthy compound for removing grease spots

is made as follows:--Take fuller’s earth, free it from all gritty matter

by elutriation with water; mix with half a pound of the earth so

prepared, half a pound of soda, as much soap, and eight yolks of eggs

well beat up with half a pound of purified ox-gall. The whole must be

carefully triturated upon a porphyry slab; the soda with the soap in the

same manner as colours are ground, mixing in gradually the eggs and the

ox-gall previously beat together. Incorporate next the soft earth by

slow degrees, till a uniform thick paste be formed, which should be made

into balls or cakes of a convenient size, and laid out to dry. A little

of this detergent being scraped off with a knife, made into a paste with

water, and applied to the stain, will remove it. Purified ox-gall is to

be diffused through its own bulk of water, applied to the spots, rubbed

well into them with the hands till they disappear, after which the stuff

is to be washed with soft water. It is the best substance for removing

stains on woollen clothes.

The redistilled oil of turpentine may also be rubbed upon the dry

clothes with a sponge or a tuft of cotton, till the spot disappear; but

it must be immediately afterwards covered with some plastic clay reduced

to powder. Without this precaution, a cloud would be formed round the

stain, as large as the part moistened with the turpentine.

Oxalic acid may be applied in powder upon the spot previously moistened

with water, well rubbed on, and then washed off with pure water.

Sulphurous acid is best generated at the moment of using it. If the

clothes be much stained, they should be suspended in an ordinary

fumigating chamber. For trifling stains, the sulphur may be burned under

the wide end of a small card or paper funnel, whose upper orifice is

applied near the cloth.

_Manipulations of the scourer._--These consist, first, in washing the

clothes in clear soft water, or in soap-water. The cloth must be next

stretched on a sloping board, and rubbed with the appropriate reagent as

above described, either by a sponge or a small hard brush. The

application of a redhot iron a little way above a moistened spot often

volatilizes the greasy matter out of it. Stains of pitch, varnish, or

oil paint, which have become dry, must first be softened with a little

fresh butter or lard, and then treated with the powder of the scouring

ball. When the gloss has been taken from silk, it may be restored by

applying the filtered mucilage of gum tragacanth; stretching it upon a

frame to dry. Ribbons are glossed with isinglass. Lemon juice is used to

brighten scarlet spots, after they have been cleaned.

SEAL ENGRAVING. The art of _engraving gems_ is one of extreme nicety.

The stone having received its desired form from the lapidary, the

engraver fixes it by cement to the end of a wooden handle, and then

draws the outline of his subject, with a brass needle or a diamond, upon

its smooth surface.

[Illustration: 969 970 971 972]

_Fig._ 969. represents the whole of the seal engraver’s lathe. It

consists of a table on which is fixed the mill, a small horizontal

cylinder of steel, into one of whose extremities the tool is inserted,

and which is made to revolve by the usual fly-wheel, driven by a

treddle. The tools that may be fitted to the mill-cylinder, are the

following: _fig._ 970. a hollow cylinder, for describing circles, and

for boring; _fig._ 971. a knobbed tool, or rod terminated by a small

ball; _fig._ 972. a stem terminated with a cutting disc, whose edge may

be either rounded, square, or sharp; being in the last case called a

saw.

Having fixed the tool best adapted to his style of work in the mill, the

artist applies to its cutting point, or edge, some diamond-powder, mixed

up with olive oil; and turning the wheel, he holds the stone against the

tool, so as to produce the wished-for delineation and erosion. A similar

apparatus is used for engraving on glass.

In order to give the highest degree of polish to the engraving, tools of

boxwood, pewter, or copper, bedaubed with moistened tripoli or

rotten-stone, and lastly, a brush, are fastened to the mill. These are

worked like the above steel instruments. Modern engravings on precious

stones, have not in general the same fine polish as the antient. The

article GEMS, in Rees’ Cyclopædia, contains a variety of valuable

information on this subject, equally interesting to the artist and the

scholar.

SEALING-WAX. (_Cire à cacheter_, Fr.; _Siegellack_, Germ.) The Hindus

from time immemorial have possessed the resin lac, and were long

accustomed to use it for sealing manuscripts before it was known in

Europe. It was first imported from the East into Venice, and then into

Spain; in which country sealing-wax became the object of a considerable

commerce, under the name of Spanish wax.

If shellac be compounded into sealing-wax, immediately after it has been

separated by fusion from the palest qualities of stick or seed lac, it

then forms a better and less brittle article, than when the shellac is

fused a second time. Hence sealing-wax, rightly prepared in the East

Indies, deserves a preference over what can be made in other countries,

where the lac is not indigenous. Shellac can be restored in some degree,

however, to a plastic and tenacious state by melting it with a very

small portion of turpentine. The palest shellac is to be selected for

bright-coloured sealing-wax, the dark kind being reserved for black.

The following prescription may be followed for making red

sealing-wax:--Take 4 ounces of shellac, 1 ounce of Venice turpentine

(some say 1-1/2 ounces), and 3 ounces of vermillion. Melt the lac in a

copper pan suspended over a clear charcoal fire, then pour the

turpentine slowly into it, and soon afterwards add the vermillion,

stirring briskly all the time of the mixture with a rod in either hand.

In forming the round sticks of sealing-wax, a certain portion of the

mass should be weighed while it is ductile, divided into the desired

number of pieces, and then rolled out upon a warm marble slab, by means

of a smooth wooden block, like that used by apothecaries for rolling a

mass of pills. The oval sticks of sealing-wax are cast in moulds, with

the above compound in a state of fusion. The marks of the lines of

junction of the mould-box may be afterwards removed by holding the

sticks over a clear fire, or passing them over a blue gas-flame. Marbled

sealing-wax is made by mixing two, three, or more coloured kinds of it,

while they are in a semi-fluid state. From the viscidity of the several

masses, their incorporation is left incomplete, so as to produce the

appearance of marbling. Gold sealing-wax is made simply by stirring

gold-coloured mica spangles into the melted resins. Wax may be scented

by introducing a little essential oil, essence of musk, or other

perfume. If 1 part of balsam of Peru be melted along with 99 parts of

the sealing-wax composition, an agreeable fragrance will be exhaled in

the act of sealing with it. Either lamp black or ivory black serves for

the colouring-matter of black wax. Sealing-wax is often adulterated with

rosin; in which case it runs into thin drops at the flame of a candle.

SEA WATER, is composed as follows, according to the author of the

article _Salines_, in the _Dictionnaire Technologique_:--Chloride of

sodium, 2·50; chloride of magnesium, 0·35; sulphate of magnesia, 0·58;

carbonates of lime and magnesia, 0·02; sulphate of lime, 0·01; water,

96·54, in 100 parts. See SALT, SEA.

SEGGAR, or SAGGER, is the cylindric case, of fire-clay, in which fine

stoneware is enclosed while being baked in the kiln.

SELENIUM, from Σεληνη, the moon, is a metalloid principle, discovered by

Berzelius, in 1817. It occurs sparingly in combination with several

metals, as lead, cobalt, copper, and quicksilver, in the Harz, at

Tilkerode; with copper and silver (_Eukairite_) in Sweden, with

tellurium and bismuth in Norway, with tellurium and gold in

Siebenbürgen, in several copper and iron pyrites, and with sulphur in

the volcanic products of the Lipari Islands. Selenium has been found

likewise in a red sediment which forms upon the bottoms of the lead

chambers in which oil of vitriol has been made from peculiar pyrites, or

pyritous sulphur. The extraction of selenium from that deposit, is a

very complex process.

Selenium, after being fused and slowly cooled, appears of a bluish-gray

colour, with a glistening surface; but it is reddish brown, and of

metallic lustre when quickly cooled, It is brittle, not very hard, and

has little tendency to assume the crystalline state. Selenium is

dark-red in powder, and transparent, with a ruby cast, in thin scales.

Its specific gravity is 4·30. It softens at the temperature of 176° F.,

is of a pasty consistence at 212°, becomes liquid at a somewhat higher

heat, forming in close vessels dark-yellow vapours, which condense into

black drops; but in the air, the fumes have a cinnabar-red colour.

This singular substance, apparently intermediate in its constitution

between sulphur and metals, has not hitherto been applied to any use in

the arts.

SELTZER WATER. See SODA-WATER, and WATERS, MINERAL.

SEPIA, is a pigment prepared from a black juice secreted by certain

glands of the cuttle-fish, which the animal ejects to darken the water

when it is pursued. One part of it is capable of making 1000 parts of

water nearly opaque. All the varieties of this mollusca secrete the same

juice; but the _Sepia officinalis_, the _Sepia ioligo_, and the _Sepia

tunicata_, are chiefly sought after for making the pigment. The first,

which occurs abundantly in the Mediterranean, affords most colour; the

sac containing it being extracted, the juice is to be dried as quickly

as possible, because it runs rapidly into putrefaction. Though insoluble

in water, it is extremely diffusible through it, and is very slowly

deposited. Caustic alkalis dissolve the sepia, and turn it brown; but in

proportion as the alkali becomes carbonated by exposure to air, the

sepia falls to the bottom of the vessel. Chlorine blanches it slowly. It

consists of carbon in an extremely divided state, along with albumine,

gelatine, and phosphate of lime.

The dried native sepia is prepared for the painter, by first triturating

it with a little caustic lye, then adding more lye, boiling the liquid

for half an hour, filtering, next saturating the alkali with an acid,

separating the precipitate, washing it with water, and finally drying it

with a gentle heat. The pigment is of a brown colour, and a fine grain.

SEPTARIA, called antiently _ludus Helmontii_, (the _quoits_ of Van

Helmont, from their form,) are lenticular concretions of clay ironstone,

intersected by veins of calc-spar, which, when calcined, and ground to

powder, form an excellent hydraulic cement. See MORTAR, HYDRAULIC.

SERPENTINE, is a mineral of the magnesian family, of a green colour; it

is scratched by calcareous spar, is sectile, tough, and therefore easily

cut into ornamental forms. It occurs in Unst and Fetlar, in Shetland; at

Portsoy, in Banffshire; in Cornwall; and the Isle of Holyhead. The

floors of bakers’ ovens are advantageously laid with slabs of

serpentine.

SHAFT, in mining, signifies a perpendicular or slightly inclined pit.

SHAGREEN. (_Chagrin_, Fr. and Germ.) The true oriental shagreen is

essentially different from all modifications of leather and parchment.

It approaches the latter somewhat, indeed, in its nature, since it

consists of a dried skin, not combined with any tanning or foreign

matter whatever. Its distinguishing characteristic is having the grain

or hair side covered over with small rough round specks or granulations.

It is prepared from the skins of horses, wild asses, and camels; of

strips cut along the chine, from the neck towards the tail, apparently

because this stronger and thicker portion of the skin is best adapted to

the operations about to be described. These fillets are to be steeped in

water till the epidermis becomes loose, and the hairs easily come away

by the roots; after which they are to be stretched upon a board, and

dressed with the currier’s fleshing-knife. They must be kept continually

moist, and extended by cords attached to their edges, with the flesh

side uppermost upon the board. Each strip now resembles a wet bladder,

and is to be stretched in an open square wooden frame by means of

strings tied to its edges, till it be as smooth and tense as a

drum-head. For this purpose it must be moistened and extended from time

to time in the frame.

The grain or hair side of the moist strip of skin must next be sprinkled

over with a kind of seeds called _Allabuta_, which are to be forced into

its surface either by tramping with the feet, or with a simple press, a

piece of felt or other thick stuff being laid upon the seeds. These

seeds belong probably to the _Chenapodium album_. They are lenticular,

hard, of a shining black colour, farinaceous within, about the size of

poppy seed, and are sometimes used to represent the eyes in wax figures.

The skin is exposed to dry in the shade, with the seeds indented into

its surface; after which it is freed from them by shaking it, and

beating upon its other side with a stick. The outside will be then

horny, and pitted with small hollows corresponding to the shape and

number of the seeds.

In order to make the next process intelligible, we must advert to

another analogous and well-known operation. When we make impressions in

fine-grained dry wood with steel punches or letters of any kind, then

plane away the wood till we come to the level of the bottom of these

impressions, afterwards steep the wood in water, the condensed or

punched points will swell above the surface, and place the letters in

relief. Snuff-boxes have been sometimes marked with prominent figures in

this way. Now shagreen is treated in a similar manner.

The strip of skin is stretched in an inclined plane, with its upper edge

attached to hooks, and its under one loaded with weights, in which

position it is thinned off with a proper semi-lunar knife, but not so

much as to touch the bottom of the seed-pits or depressions. By

maceration in water, the skin is then made to swell, and the pits become

prominent over the surface which had been shaved. The swelling is

completed by steeping the strips in a warm solution of soda, after which

they are cleansed by the action of salt brine, and then dyed.

In the East the following processes are pursued. Entirely white shagreen

is obtained by imbuing the skin with a solution of alum, covering it

with the dough made with Turkey wheat, and after a time washing this

away with a solution of alum. The strips are now rubbed with grease or

suet, to diminish their rigidity, then worked carefully in hot water,

curried with a blunt knife, and afterwards dried. They are dyed red with

decoction of cochineal or kermes, and green with fine copper filings and

sal ammoniac, the solution of this salt being first applied, then the

filings being strewed upon the skin, which must be rolled up and loaded

with weights for some time; blue is given with indigo, quicklime, soda,

and honey; and black, with galls and copperas.

SHALE, or SLATE-CLAY, is an important stratiform member of the

coal-measures. See PITCOAL.

SHAMOY LEATHER. See LEATHER.

SHEATHING OF SHIPS. For this purpose many different metals and metallic

alloys have been lately proposed. From a train of researches which I

made for an eminent copper company, a few years ago, upon various

specimens of sheathing which had been exposed upon ships during many

voyages, it appeared that copper containing a minute but definite

proportion of tin, was by far the most durable.

SHELLAC. See LAC, and SEALING-WAX.

SIENITE, is a granular aggregated compound rock, consisting of felspar

and hornblende, sometimes mixed with a little quartz and mica. The

hornblende is the characteristic ingredient, and serves to distinguish

sienite from granite, with which it has been sometimes confounded;

though the felspar, which is generally red, is the more abundant

constituent. The Egyptian sienite, containing but little hornblende,

with a good deal of quartz and mica, approaches most nearly to granite.

It is equally metalliferous with porphyry; in the island of Cyprus, it

is rich in copper; and in Hungary, it contains many valuable gold and

silver mines.

Sienite forms a considerable part of the Criffle, a hill in Galloway. It

takes its name from the city of Syene, in the Thebaid, near the

cataracts of the Nile, where this rock abounds. It is an excellent

building-stone, and was imported in large quantities from Egypt by the

Romans, for the architectural and statuary decorations of their capital.

SILICA and SILICON. (_Silice_, _silicium_, Fr.; _Kieselerde_, _kiesel_,

Germ.) Silica was till lately ranked among the earths proper; but since

the researches of Davy and Berzelius, it has been transferred to the

chemical class of acids. It constitutes the principal portion of most of

the hard stones and minerals which compose the crust of the globe;

occurring nearly pure in rock crystal, quartz, agate, calcedony, flint,

&c. Silica or silicic acid may be obtained perfectly pure, and also in

the finest state of comminution, by taking the precipitate formed by

passing silicated fluoric gas through water, filtering, washing, and

igniting it, to expel the last traces of the fluoride of silicon. The

powder thus obtained is so light as to be blown away with the least

breath of air. Silica may be more conveniently procured, however, by

fusing ground flint with four times its weight of a mixture, in equal

parts, of dry carbonate of potassa and carbonate of soda, in a platinum

or silver crucible. The alkaline carbonates should be first fused, and

the flint powder sprinkled into the liquid, as long as it dissolves with

effervescence. The mass is to be then allowed to cool, dissolved in

dilute muriatic acid; the solution is to be filtered, and evaporated to

dryness; the dry crust is to be pulverized, digested for two hours with

a little muriatic acid, to remove any iron and alumina that may be

present, next washed with hot water, drained, dried, and ignited.

The above silicate of potassa and soda is the compound called soluble

glass, which applied in solution to the surface of wood, calico, paper,

&c., renders them unsusceptible of taking fire on the contact of an

ignited body.

Silica, as thus prepared, is a white powder, rough to the touch, gritty

between the teeth, absolutely insoluble in water, acids, and most

liquids. Its specific gravity is 2·66. It cannot be fused by the most

intense heat of our furnaces, but at the flame of the oxy-hydrogen

blowpipe it melts into a limpid colourless glass. By peculiar chemical

methods, an aqueous solution of it may be made artificially, similar to

what nature presents us with in many thermal springs, as in those of

Reikum and of Geyser in Iceland, and of most mineral waters, in minute

quantity. There is no acid except the fluoric which can directly

dissolve dry or calcined silica. Silica is composed of 48·04 silicon,

and 51·96 oxygen.

SILICATES, are compounds of silicic acid (silica), with the bases

alumina, lime, magnesia, potassa, soda, &c. They constitute the greater

number by far of the hard minerals which encrust the terrestrial globe.

Thus cyanite is a subsilicate of alumina; felspar and leucite, are

silicates of alumina and potassa; albite and analcime, are silicates of

alumina and soda; stilbite, prehnite, mesolite, labradorite, tourmaline,

mica, &c., are silicates of alumina and lime; chrysolite, steatite,

serpentine, and meerschaum, are silicates of magnesia; augite and

hornblende, are silicates of lime and magnesia, &c.

SILICON, called also silicium, may be obtained by burning potassium in

silicated fluoric gas. The product of the combustion is a brown cinder,

which, on being thrown into water, disengages hydrogen with violence,

and lets fall a dark liver-brown powder, upon which water exercises no

action. This matter is silicon mixed with a salt of difficult solution,

which is composed of fluorine, potassium, and silicon. This salt may,

however, be removed by a great deal of washing. The further details of

this curious subject will be given in my forthcoming system of

chemistry.

SILK MANUFACTURE. (_Fabrique de soie_, Fr.; _Seidenfabrik_, Germ.) This

may be divided into two branches: 1. the production of raw silk; 2. its

filature and preparation in the mill, for the purposes of the weaver and

other textile artisans. The threads, as spun by the silkworm, and wound

up in its cocoon, are all twins, in consequence of the twin orifice in

the nose of the insect through which they are projected. These two

threads are laid parallel to each other, and are glued more or less

evenly together by a kind of glossy varnish, which also envelopes them,

constituting nearly 25 per cent. of their weight. Each ultimate filament

measures about 1/2000 of an inch in average fine silk, and the pair

measures of course fully 1/1000 of an inch. In the raw silk, as imported

from Italy, France, China, &c., several of these twin filaments are

slightly twisted and agglutinated to form one thread, called a single.

The specific gravity of silk is 1·300, water being 1·000. It is by far

the most tenacious or the strongest of all textile fibres, a thread of

it of a certain diameter being nearly three times stronger than a thread

of flax, and twice stronger than hemp. Some varieties of silk are

perfectly white, but the general colour in the native state is a golden

yellow.

The production of silk was unknown in Europe till the sixth century,

when two monks, who brought some eggs of the silkworm from China or

India to Constantinople, were encouraged to breed the insect, and

cultivate its cocoons, by the Emperor Justinian. Several silk

manufactures were in consequence established in Athens, Thebes, and

Corinth, not only for rearing the worm upon mulberry-leaves, but for

unwinding its cocoons, for twisting their filaments into stronger

threads, and weaving these into robes. The Venetians having then and

long afterwards intimate commercial relations with the Greek empire,

supplied the whole of western Europe with silk goods, and derived great

riches from the trade.

About 1130, Roger II., king of Sicily, set up a silk manufacture at

Palermo, and another in Calabria, conducted by artisans whom he had

seized and carried off as prisoners of war in his expedition to the Holy

Land. From these countries, the silk industry soon spread throughout

Italy. It seems to have been introduced into Spain at a very early

period, by the Moors, particularly in Murcia, Cordova, and Granada. The

last town, indeed, possessed a flourishing silk trade when it was taken

by Ferdinand in the 15th century. The French having been supplied with

workmen from Milan, commenced, in 1521, the silk manufacture; but it was

not till 1564 that they began successfully to produce the silk itself,

when Traucat, a working gardener at Nismes, formed the first nursery of

white mulberry-trees, and with such success, that in a few years he was

enabled to propagate them over many of the southern provinces of France.

Prior to this time, some French noblemen, on their return from the

conquest of Naples, had introduced a few silkworms with the mulberry

into Dauphiny; but the business had not prospered in their hands. The

mulberry plantations were greatly encouraged by Henry IV.; and since

then they have been the source of most beneficial employment to the

French people. James I. was most solicitous to introduce the breeding of

silkworms into England, and in a speech from the throne he earnestly

recommended his subjects to plant mulberry-trees; but he totally failed

in the project. This country does not seem to be well adapted for this

species of husbandry, on account of the great prevalence of blighting

east winds during the months of April and May, when the worms require a

plentiful supply of mulberry-leaves. The manufacture of silk goods,

however, made great progress during that king’s peaceful and pompous

reign. In 1629 it had become so considerable in London, that the

silk-throwsters of the city and suburbs were formed into a public

corporation. So early as 1661 they employed 40,000 persons. The

revocation of the edict of Nantes, in 1685, contributed in a remarkable

manner to the increase of the English silk trade, by the influx of a

large colony of skilful French weavers, who settled in Spitalfields. The

great silk-throwing mill mounted at Derby, in 1719, also served to

promote the extension of this branch of manufacture; for soon

afterwards, in the year 1730, the English silk goods bore a higher price

in Italy than those made by the Italians, according to the testimony of

Keysler.

Till the year 1826, however, our silk manufactures in general laboured

under very grievous fiscal burdens. Foreign organzine, or twisted raw

silk, paid an import duty of 14_s._ 7-1/2_d._ per pound; raw Bengal

silk, 4_s._; and that from other places, 5_s._ 7-1/2_d._ Mr. Huskisson

introduced a bill at that time, reducing the duty on organzine to 5_s._,

and the duty on other raw silk to 3_d._ per pound. The total prohibition

of the import of French manufactured silks, which gave rise to so much

contraband trade, was also converted into a duty of 30 per cent. _ad

valorem_. During the reign of the prohibitory system, when our silk

weavers had no variety of patterns to imitate, and no adequate stimulus

to excel, on account of the monopoly which they possessed in the home

market, the inferiority of their productions was a subject of constant

pride and congratulation among the Lyonnais; and accordingly the English

could not stand their competition any where. At that time, the

disadvantage on English silk goods, compared to French, was estimated in

foreign markets at 40 per cent.; of late years it certainly does not

exceed 20, notwithstanding the many peculiar facilities which France

enjoys for this her favourite staple.

The silkworm, called by entomologists _Phalæna bombyx mori_, is, like

its kindred species, subject to four metamorphoses. The egg, fostered by

the genial warmth of spring, sends forth a caterpillar, which, in its

progressive enlargement, casts its skin either three or four times,

according to the variety of the insect. Having acquired its full size in

the course of 25 or 30 days, and ceasing to eat during the remainder of

its life, it begins to discharge a viscid secretion, in the form of

pulpy twin filaments, from its nose, which harden in the air. These

threads are instinctively coiled into an ovoid nest round itself, called

a cocoon, which serves as a defence against living enemies and changes

of temperature. Here it soon changes into the chrysalis or nymph state,

in which it lies swaddled, as it were, for about 15 or 20 days. Then it

bursts its cearments, and comes forth furnished with appropriate wings,

antennæ, and feet, for living in its new element, the atmosphere. The

male and the female moths couple together at this time, and terminate

their union by a speedy death, their whole existence being limited to

two months. The cocoons are completely formed in the course of three or

four days; the finest being reserved as seed worms. From these cocoons,

after an interval of 18 or 20 days, the moth makes its appearance,

perforating its tomb by knocking with its head against one end of the

cocoon, after softening it with saliva, and thus rendering the filaments

more easily torn asunder by its claws. Such moths or aurelias are

collected and placed upon a piece of soft cloth, where they couple and

lay their eggs.

The eggs, or grains as they are usually termed, are enveloped in a

liquid which causes them to adhere to the piece of cloth or paper on

which the female lays them. From this glue they are readily freed, by

dipping them in cold water, and wiping them dry. They are best preserved

in the _ovum_ state at a temperature of about 55° F. If the heat of

spring advances rapidly in April, it must not be suffered to act on the

eggs, otherwise it might hatch the caterpillars long before the mulberry

has sent forth its leaves to nourish them. Another reason for keeping

back their incubation is, that they may be hatched together in large

broods, and not by small numbers in succession. The eggs are made up

into small packets, of an ounce, or somewhat more, which in the south of

France are generally attached to the girdles of the women during the

day, and placed under their pillows at night. They are, of course,

carefully examined from time to time. In large establishments, they are

placed in an appropriate stove-room, where they are exposed to a

temperature gradually increased till it reaches the 86th degree of

Fahrenheit’s scale, which term it must not exceed. Aided by this heat,

nature completes her mysterious work of incubation in eight or ten days.

The teeming eggs are now covered with a sheet of paper pierced with

numerous holes, about one-twelfth of an inch in diameter. Through these

apertures the new-hatched worms creep upwards instinctively, to get at

the tender mulberry leaves strewed over the paper.

The nursery where the worms are reared, is called by the French a

_magnanière_; it ought to be a well-aired chamber, free from damp,

excess of cold or heat, rats and other vermin. It should be ventilated

occasionally, to purify the atmosphere from the noisome emanations

produced by the excrements of the caterpillars and the decayed leaves.

The scaffolding of the wicker-work shelves should be substantial; and

they should be from 15 to 18 inches apart. A separate small apartment

should be allotted to the sickly worms. Immediately before each

moulting, the appetite of the worms begins to flag; it ceases altogether

at that period of cutaneous metamorphosis, but revives speedily after

the skin is fairly cast, because the internal parts of the animal are

thereby allowed freely to develop themselves. At the end of the second

age, the worms are half an inch long; and should then be transferred

from the small room in which they were first hatched, into the proper

apartment where they are to be brought to maturity and set to spin

their balls. On occasion of changing their abode, they must be well

cleansed from the litter, laid upon beds of fresh leaves, and supplied

with an abundance of food every six hours in succession. In shifting

their bed, a piece of network being laid over the wicker plates, and

covered with leaves, the worms will creep up over them; when they may be

transferred in a body upon the net. The litter, as well as the sickly

worms, may thus be readily removed, without handling a single healthy

one. After the third age, they may be fed with entire leaves; because

they are now exceedingly voracious, and must not be subsequently stinted

in their diet. The exposure of chloride of lime, spread thin upon

plates, to the air of the _magnanière_, has been found useful in

counteracting the tendency which sometimes appears of an epidemic

disease among the silkworms, from the fetid exhalations of the dead and

dying.

When they have ceased to eat, either in the fourth or fifth age,

agreeably to the variety of the _bombyx_, and when they display the

spinning instinct by crawling up among the twigs of heath, &c., they are

not long of beginning to construct their cocoons, by throwing the thread

in different directions, so as to form the floss, filoselle, or outer

open network, which constitutes the _bourre_ or silk for carding and

spinning.

The cocoons destined for filature, must not be allowed to remain for

many days with the worms alive within them; for should the chrysalis

have leisure to grow mature or come out, the filaments at one end would

be cut through, and thus lose almost all their value. It is therefore

necessary to extinguish the life of the animal by heat, which is done

either by exposing the cocoons for a few days to sunshine, by placing

them in a hot oven, or in the steam of boiling water. A heat of 202° F.

is sufficient for effecting this purpose, and it may be best

administered by plunging tin cases filled with the cocoons into water

heated to that pitch.

80 pounds French (88 Eng.) of cocoons, are the average produce from one

ounce of eggs, or 100 from one ounce and a quarter; but M. Folzer of

Alsace obtained no less than 165 pounds. The silk obtained from a cocoon

is from 750 to 1150 feet long. The varnish by which the coils are glued

slightly together, is soluble in warm water.

The silk husbandry, as it may be called, is completed in France within

six weeks from the end of April, and thus affords the most rapid of

agricultural returns, requiring merely the advance of a little capital

for the purchase of the leaf. In buying up cocoons, and in the filature,

indeed, capital may be often laid out to great advantage. The most

hazardous period in the process of breeding the worms, is at the third

and fourth moulting; for upon the 6th day of the third age, and the

seventh day of the fourth, they in general eat nothing at all. On the

first day of the fourth age, the worms proceeding from one ounce of eggs

will, according to Bonafons, consume upon an average twenty-three pounds

and a quarter of mulberry leaves; on the first of the fifth age, they

will consume forty-two pounds; and on the sixth day of the same age,

they acquire their maximum voracity, devouring no less than 223 pounds.

From this date their appetite continually decreases, till on the tenth

day of this age they consume only fifty-six pounds. The space which they

occupy upon the wicker tables, being at their birth only nine feet

square, becomes eventually 239 feet. In general the more food they

consume, the more silk will they produce.

A mulberry-tree is valued, in Provence, at from 6_d._ to 10_d._; it is

planted out of the nursery at four years of age; it is begun to be

stripped in the fifth year, and affords an increasing crop of leaves

till the twentieth. It yields from 1 cwt. to 30 cwt. of leaves,

according to its magnitude and mode of cultivation. One ounce of

silkworm eggs is worth in France about 2-1/2 francs; it requires for its

due development into cocoons about 15 cwt. of mulberry leaves, which

cost upon an average 3 francs per cwt. in a favourable season. One ounce

of eggs is calculated, as I have said, to produce from 80 to 100 pounds

of cocoons, of the value of 1 fr. 52 centimes per pound, or 125 francs

in whole. About 8 pounds of reeled raw silk, worth 18 francs a pound,

are obtained from these 100 pounds of cocoons.

There are three denominations of raw silk; viz., organzine, _trame_

(shute or tram), and floss. Organzine serves for the warp of the best

silk stuffs, and is considerably twisted; tram is made usually from

inferior silk, and is very slightly twisted, in order that it may spread

more, and cover better in the weft; floss, or _bourre_, consists of the

shorter broken silk, which is carded and spun like cotton. Organzine and

trame may contain from 3 to 30 twin filaments of the worm; the former

possesses a double twist, the component filaments being first twisted in

one direction, and the compound thread in the opposite; the latter

receives merely a slender single twist. Each twin filament gradually

diminishes in thickness and strength, from the surface of the cocoon,

where the animal begins its work in a state of vigour, to the centre,

where it finishes it, in a state of debility and exhaustion; because it

can receive no food from the moment of its beginning to spin by spouting

forth its silky substance. The winder is attentive to this progressive

attenuation, and introduces the commencement of some cocoons to

compensate for the termination of others. The quality of raw silk

depends, therefore, very much upon the skill and care bestowed upon its

filature. The softest and purest water should be used in the cocoon

kettle.

The quality of the raw silk is determined by first winding off 400 ells

of it, equal to 475 metres, round a drum one ell in circumference, and

then weighing that length. The weight is expressed in grains, 24 of

which constitute one denier; 24 deniers constitute one ounce; and 16

ounces make one pound, _poids de marc_. This is the Lyons rule for

valuing silk. The weight of a thread of raw silk 400 ells long, is two

grains and a half, when five twin filaments have been reeled and

associated together.

Raw silk is so absorbent of moisture, that it may be increased ten per

cent. in weight by this means. This property has led to falsifications;

which are detected by enclosing weighed portions of the suspected silk

in a wire-cloth cage, and exposing it to a stove-heat of about 78° F.

for 24 hours, with a current of air. The loss of weight which it thereby

undergoes, demonstrates the amount of the fraud. There is an office in

Lyons called the _Condition_, where this assay is made, and by the

report of which the silk is bought and sold. The law in France requires,

that all the silk tried by the _Condition_ must be worked up into

fabrics in that country.

In the Journal of the Asiatic Society of Bengal, for January, 1837,

there are two very valuable papers upon silkworms; the first, upon those

of Assam, by Mr. Thomas Hugon, stationed at Nowgong; the second by Dr.

Heifer, upon those which are indigenous to India. Besides the _Bombyx

mori_, the Doctor enumerates the following seven species, formerly

unknown:--1. The wild silkworm of the central provinces, a moth not

larger than the _Bombyx mori_. 2. The Joree silkworm of Assam, _Bombyx

religiosæ_, which spins a cocoon of a fine filament, with much lustre.

It lives upon the pipul tree (_Ficus religiosa_), which abounds in

India, and ought therefore to be turned to account in breeding this

valuable moth. 3. _Saturnia silhetica_, which inhabits the cassia

mountains in Silhet and Dacca, where its large cocoons are spun into

silk. 4. A still larger _Saturnia_, one of the greatest moths in

existence, measuring ten inches from the one end of the wing to the

other; observed by Mr. Grant, in _Chirra Punjee_. 5. _Saturnia paphia_,

or the Tusseh silkworm, is the most common of the native species, and

furnishes the cloth usually worn by Europeans in India. It has not

hitherto been domesticated, but millions of its cocoons are annually

collected in the jungles, and brought to the silk factories near

Calcutta and Bhagelpur. It feeds most commonly on the hair-tree

(_Zizyphus jujuba_), but it prefers the _Terminalia alata_, or Assam

tree, and the _Bombax heptaphyllum_. It is called _Koutkuri mooga_, in

Assam. 6. Another _Saturnia_, from the neighbourhood of Comercolly. 7.

_Saturnia assamensis_, with a cocoon of a yellow-brown colour, different

from all others, called _mooga_, in Assam; which, although it can be

reared in houses, thrives best in the open air upon trees, of which

seven different kinds afford it food. The _Mazankoory mooga_, which

feeds on the Adakoory tree, produces a fine silk, which is nearly white,

and fetches 50 per cent. more than the fawn-coloured. The trees of the

first year’s growth produce by far the most valuable cocoons. The mooga

which inhabits the soom-tree, is found principally in the forests of the

plains, and in the villages. The tree grows to a large size, and yields

three crops of leaves in the year. The silk is of a light fawn colour,

and ranks next in value to the Mazankoory. There are generally five

breeds of mooga worms in the year; 1. in January and February; 2. in May

and June; 3. in June and July; 4. in August and September; 5. in October

and November; the first and last being the most valuable.

The Assamese select for breeding, such cocoons only as have been begun

to be formed in the largest number on the same day, usually the second

or third after the commencement; those which contain males being

distinguishable by a more pointed end. They are put in a closed basket

suspended from the roof; the moths, as they come forth, having room to

move about, after a day, the females (known only by their large body)

are taken out, and tied to small wisps of thatching-straw, selected

always from over the hearth, its darkened colour being thought more

acceptable to the insect. If out of a batch, there should be but few

males, the wisps with the females tied to them are exposed outside at

night; and the males thrown away in the neighbourhood find their way to

them. These wisps are hung upon a string tied across the roof, to keep

them from vermin. The eggs laid after the first three days are said to

produce weak worms. The wisps are taken out morning and evening, and

exposed to the sunshine, and in ten days after being laid, a few of them

are hatched. The wisps being then hung up to the tree, the young worms

find their way to the leaves. The ants, whose bite is fatal to the worm

in its early stages, are destroyed by rubbing the trunk of the tree with

molasses, and tying dead fish and toads to it, to attract these

rapacious insects in large numbers, when they are destroyed with fire; a

process which needs to be repeated several times. The ground under the

trees is also well cleared, to render it easy to pick up and replace the

worms which fall down. They are prevented from coming to the ground by

tying fresh plantain-leaves round the trunk, over whose slippery surface

they cannot crawl; and they are transferred from exhausted trees to

fresh ones, on bamboo platters tied to long poles. The worms require to

be constantly watched and protected from the depredations of both day

and night birds, as well as rats and other vermin. During their

moultings, they remain on the branches; but when about beginning to

spin, they come down the trunk, and being stopped by the

plantain-leaves, are there collected in baskets, which are afterwards

put under bunches of dry leaves, suspended from the roof, into which the

worms crawl, and form their cocoons--several being clustered together:

this accident, due to the practice of crowding the worms together, which

is most injudicious, rendering it impossible to wind off their silk in

continuous threads, as in the filatures of Italy, France, and even

Bengal. The silk is, therefore, spun like flax, instead of being unwound

in single filaments. After four days the proper cocoons are selected for

the next breed, and the rest are uncoiled. The total duration of a breed

varies from 60 to 70 days; divided into the following periods:--

Four moultings, with one day’s illness attending each 20

From fourth moulting to beginning of cocoon 10

In the cocoon 20, as a moth 6, hatching of eggs 10 36

On being tapped with the finger, the body renders a hollow sound; the

quality of which shows whether they have come down for want of leaves on

the tree, or from their having ceased feeding.

As the chrysalis is not soon killed by exposure to the sun, the cocoons

are put on stages, covered up with leaves, and exposed to the hot air

from grass burned under them; they are next boiled for about an hour in

a solution of the potash, made from incinerated rice-stalks; then taken

out, and laid on cloth folded over them to keep them warm. The floss

being removed by hand, they are then thrown into a basin of hot water to

be unwound; which is done in a very rude and wasteful way.

The plantations for the mooga silkworm in Lower Assam, amount to 5000

acres, besides what the forests contain; and yield 1500 maunds of 84

lbs. each per annum. Upper Assam is more productive.

The cocoon of the _Koutkuri mooga_ is of the size of a fowl’s egg. It is

a wild species, and affords filaments much valued for fishing-lines. See

SILKWORM GUT.

8. The _Arrindy_, or _Eria_ worm, and moth, is reared over a great part

of Hindustan, but entirely within doors. It is fed principally on the

_Hera_, or _Palma christi_ leaves, and gives sometimes 12 broods of spun

silk in the course of a year. It affords a fibre which looks rough at

first; but when woven, becomes soft and silky, after repeated washings.

The poorest people are clothed with stuff made of it, which is so

durable as to descend from mother to daughter. The cocoons are put in a

closed basket, and hung up in the house, out of reach of rats and

insects. When the moths come forth, they are allowed to move about in

the basket for twenty-four hours; after which the females are tied to

long reeds or canes, twenty or twenty-five to each, and these are hung

up in the house. The eggs that are laid the first three days, amounting

to about 200, alone are kept; they are tied up in a cloth, and suspended

to the roof till a few begin to hatch. These eggs are white, and of the

size of turnip-seed. When a few of the worms are hatched, the cloths are

put on small bamboo platters hung up in the house, in which they are fed

with tender leaves. After the second moulting, they are removed to

bunches of leaves suspended above the ground, beneath which a mat is

laid to receive them when they fall. When they cease to feed, they are

thrown into baskets full of dry leaves, among which they form their

cocoons, two or three being often found joined together. Upon this

injudicious practice I have already animadverted.

9. The _Saturnia trifenestrata_, has a yellow cocoon of a remarkably

silky lustre. It lives on the soom-tree in Assam, but seems not to be

much used.

[Illustration: 973 974]

The mechanism of the silk filature, as lately improved in France, is

very ingenious. _Figs._ 973. and 974. exhibit it in plan and

longitudinal view. _a_ is an oblong copper basin containing water heated

by a stove or by steam. It is usually divided by transverse partitions

into several compartments, containing 20 cocoons, of which there are 5

in one group, as shown in the figure. _b_, _b_, are wires with hooks or

eyelets at their ends, through which the filaments run, apart, and are

kept from ravelling. _c_, _c_, the points where the filaments cross and

rub each other, on purpose to clean their surfaces. _d_, is a spiral

groove, working upon a pin point, to give the traverse motion

alternately to right and left, whereby the thread is spread evenly over

the surface of the reel _e_. _f_, _f_, are the pulleys, which by means

of cords transmit the rotatory movement of the cylinder _d_, to the reel

_e_. _g_, is a friction lever or tumbler, for lightening or slackening

the endless cord, in the act of starting or stopping the winding

operation. Every apartment of a large filature contains usually a series

of such reels as the above, all driven by one prime mover; each of

which, however, may by means of the tumbling lever be stopped at

pleasure. The reeler is careful to remove any slight adhesions, by the

application of a brush in the progress of her work.

The expense of reeling the excellent Cevennes silk is only 3 francs and

50 centimes per Alais pound; from 4 to 5 cocoons going to one thread.

That pound is 92 hundredths of our avoirdupois pound. In Italy, the cost

of reeling silk is much higher, being 7 Italian livres per pound, when 3

to 4 cocoons go to the formation of one thread; and 6 livres when there

are from 4 to 5 cocoons. The first of these raw silks will have a

_titre_ of 20 to 24 deniers; the last, of 24 to 28. If 5 to 6 cocoons go

to one thread, the titre will be from 26 to 32 deniers, according to the

quality of the cocoons. The Italian livre is worth 7-1/2_d._ English.

The woman employed at the kettle receives one livre and five sous per

day; and the girl who turns the reel, gets thirteen sous a day; both

receiving board and lodging in addition. In June, July, and August, they

work 16 hours a day, and then they wind a _rubo_ or ten pounds weight of

cocoons, which yield from 1-5th to 1-6th of silk, when the quality is

good. The whole expenses amount to from 6 to 7 livres upon every ten

pounds of cocoons; which is about 2_s._ 8_d._ per English pound of raw

silk.

The raw silk, as imported into this country in hanks from the filatures,

requires to be regularly wound upon bobbins, doubled, twisted, and

reeled in our silk-mills. These processes are called _throwing_ silk,

and their proprietors are called silk _throwsters_; terms probably

derived from the appearance of swinging or tossing which the silk

threads exhibit during their rapid movements among the machinery of the

mills.

A representation of a French mill for throwing silk, is given in the

_Dictionnaire Technologique_, under the article _Moulinage de Soie_. But

it is a most awkward, operose, and defective piece of machinery, quite

unworthy of being presented to my readers. It was in Manchester that

throwing-mills received the grand improvement upon the antient Italian

plan, which had been originally introduced into this country by Sir

Thomas Lombe, and erected at Derby. That improvement is chiefly due to

the eminent factory engineers, Messrs. Fairbairn and Lillie, who

transferred to silk the elegant mechanism of the throstle, so well known

in the cotton trade. Still, throughout the silk districts of France the

throwing mills are generally small, not many of them turning off more

than 1000 pounds of organzine per annum, and not involving 5000_l._ of

capital. The average price of throwing organzine in that country, where

the throwster is not answerable for loss, is 7 francs; of throwing

trame, from 4 fr. to 5 fr. (per kilogramme?) Where the throwster is

accountable for loss, the price is from 10 fr. to 11 fr. for organzine,

and from 6 to 7 for trame. In Italy, throwing adds 3_s._ 9_d._ to the

price of raw silk, upon an average. I should imagine, from the

perfection and speed of the silk-throwing machinery in this country, as

about to be described, that the cost of converting a pound of raw silk

either into organzine or _trame_ must be considerably under any of the

above sums.

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