{1. Pure ores } Pesey, Spain,
{ } &c.
{
{2. Ores mixed } England, in
{ with saline} general.
{ gangues. }
{
{3. Ores mixed { Viconago in
{ with earthy{ Italy, and
{ A { gangues. { Redruth in
{ De-sulphura- { { Cornwall.
{ tion by {
{ roasting. {4. Ores mixed }
{ { with sever-} Combined with
{ { al sul- } the above.
{ { phurets. }
I. Class. { {
Treated in { {5. Ores with }
reverberatory { { earthy sa- }
furnaces. { { line, and }
{ { sulphurous }
{ { gangues. }
{
{ {6. Ores with }
{ B { mattes, as } Vienne, Poul-
{ De-sulphura- { at Vienne, } laouen, and
{ tion by iron. { in Dauphi- } Tarnowitz.
{ ny. }
{7. Ores pro- { Mattes, with }Many
{ ducing { raw lead. }places.
{ slags of } Workable lead,{
{ A { various } without {Villefort.
{ Founding after{ silicates. } mattes. {
{ roasting in a {
{ heap, or in a {8. Ores pro- { Mattes and }Several
II. Class. { reverberatory.{ ducing com-{ workable lead.}places.
Treated in { { pound sili-{ Workable {Pont Gibaud
the mill-slag-{ { cate slags.{ lead. {and Scotch
hearth, the { { { {furnace.
_fourneau à_ {
_manche_, or { B }9. Ores pro- { Mattes and }Baad-Ems,
Scotch fur- { Founding with } ducing { workable }Hartz,
nace. { direct de- } slags com- { lead. }Tarnowitz.
{ sulphuration } posed of } Poor mattes {
{ by metallic } silicates } and workable {Tarnowitz.
{ iron. } and sub- } lead. {
{ } silicates. }
{
The annual production of lead in Europe may be estimated at about 80,000
tons; of which four-sevenths are produced in England, two-sevenths in
Spain, the remainder in Germany and Russia. France does not produce more
than one five-hundredth part of the whole; and only one-fiftieth of its
consumption.
See LITHARGE, MINIUM, or _Red Lead_, SOLDER, SUGAR or _Acetate_ of LEAD,
TYPE METAL, and WHITE LEAD.
LEAD-SHOT; (_Plomb de chasse_, Fr.; _Schrot_, _Flintenschrot_, Germ.)
The origin of most of the imperfections in the manufacture of lead-shot
is the too rapid cooling of the spherules by their being dropped too hot
into the water, whereby their surfaces form a solid crust, while their
interior remains fluid, and in its subsequent concretion, shrinks, so as
to produce the irregularities of the shot.
The patent shot towers originally constructed in England obviate this
evil by exposing the fused spherules after they pass through the
cullender, to a large body of air during their descent into the water
tub placed on the ground. The greatest erection of this kind is probably
at Villach in Carinthia, being 240 Vienna, or 249 English feet high.
The quantity of arsenic added to the mass of melted lead, varies
according to the quality of this metal; the harder and less ductile the
lead is, the more arsenic must be added. About 3 pounds of either white
arsenic or orpiment is enough for one thousand parts of soft lead, and
about 8 for the coarser kinds. The latter are employed preferably for
shot, as they are cheaper and answer sufficiently well. The arsenical
alloy is made either by introducing some of this substance at each
melting; or by making a quantity of the compound considerably stronger
at once, and adding a certain portion of this to each charge of lead. If
the particles of the shot appear lens-shaped, it is a proof that the
proportion of arsenic has been too great; but if they are flattened upon
one side, if they are hollowed in their middle, called _cupping_ by the
workman, or drag with a tail behind them, the proportion of arsenic is
too small.
The following is the process prescribed by the patentees, Ackerman and
Martin. Melt a ton of soft lead, and sprinkle round its sides in the
iron pot, about two shovelfuls of wood ashes, taking care to leave the
centre clear; then put into the middle about 40 pounds of arsenic to
form a rich alloy with the lead. Cover the pot with an iron lid, and
lute the joints quickly with loam or mortar to confine the arsenical
vapours, keeping up a moderate fire to maintain the mixture fluid for
three or four hours; after which skim carefully, and run the alloy into
moulds to form ingots or pigs. The composition thus made is to be put in
the proportion of one pig or ingot into 1000 pounds of melted ordinary
lead. When the whole is well combined, take a perforated skimmer and let
a few drops of it fall from some height into a tub of water. If they do
not appear globular, some more arsenical alloy must be added.
Lead which contains a good deal of pewter or tin must be rejected,
because it tends to produce elongated drops or tails.
From two to three tons are usually melted at once in the large
establishments. The surface of the lead gets covered with a crust of
oxide of a white spongy nature, sometimes called _cream_ by the workmen,
which is of use to coat over the bottom of the cullender, because
without such a bed the heavy melted lead would run too rapidly through
the holes for the granulating process, and would form oblong spheroids.
The mounting of this filter, or lining of the cullender, is reckoned to
be a nice operation by the workmen, and is regarded usually as a
valuable secret.
The cullenders are hollow hemispheres of sheet iron about 10 inches in
diameter, perforated with holes, which should be perfectly round and
free from burs. These must be of an uniform size in each cullender; but
of course a series of different cullenders with sorted holes for every
different size of lead shot, must be prepared. The holes have nearly the
following diameters for the annexed numbers of shot.
No. 0. 1/50 of an inch.
1. 1/58 --
2. 1/66 --
3. 1/72 --
4. 1/80 --
From No. 5. to No. 9. the diameter decreases by regular gradations, the
latter being only 1/360 of an inch.
The operation is always carried on with three cullenders at a time;
which are supported upon projecting grates of a kind of chafing dish
made of sheet iron somewhat like a triangle. This chafing dish should be
placed immediately above the fall; while at its bottom there must be a
tub half filled with water for receiving the granulated lead. The
cullenders are not in contact, but must be parted by burning charcoal in
order to keep the lead constantly at the proper temperature, and to
prevent its solidifying in the filter. The temperature of the lead bath
should vary with the size of the shot; for the largest, it should be
such that a bit of straw plunged into it will be scarcely browned, but
for all it should be nicely regulated. The height from which the
particles should be let fall varies likewise with the size of the shot;
as the congelation is the more rapid, the smaller they are. With a fall
of 33 yards or 100 feet, from No. 4. to No. 9. may be made; but for
larger sizes, 150 feet of height will be required.
Every thing being arranged as above described, the workman puts the
filter-stuff into the cullender, pressing it well against the sides. He
next pours lead into it with an iron ladle, but not in too great
quantity at a time, lest it should run through too fast. The shot
thereby formed and found in the tub are not all equal.
The centre of the cullender being less hot affords larger shot than the
sides, which are constantly surrounded with burning charcoal.
Occasionally, also, the three cullenders employed together may have
holes of different sizes, in which case the tub may contain shot of very
various magnitudes. These are separated from each other by square sieves
of different fineness, 10 inches broad and 16 inches long, their bottoms
being of sheet iron pierced with holes of the same diameters as those of
the cullenders. These sieves are suspended by means of two bands above
boxes for receiving the shot; one sieve being usually set above another
in consecutive numbers, for instance 1 and 2. The shot being put into
the upper sieve, No. O. will remain in it, No. 1. will remain in the
lower sieve, and No. 2. will, with all the others, pass through it into
the chest below. It is obvious that by substituting sieves of successive
fineness, shot of any dimension may be sorted.
In the preceding process the shot has been sorted to size; it must next
be sorted to form, so as to separate all the spheroids which are not
truly round, or are defective in any respect. For this purpose a board
is made use of about 27 inches long and 16 broad, furnished partially
with upright ledges; upon this tray a handful or two of the shot to be
sorted being laid, it is inclined very slightly, and gently shaken in
the horizontal direction, when the globular particles run down by one
edge, into a chest set to receive them, while those of irregular forms
remain on the sides of the tray, and are reserved to be re-melted.
After being sorted in this way, the shot requires still to be smoothed
and polished bright. This object is effected by putting it into a small
octagonal cask, through a door in its side, turning upon a horizontal
iron axis, which rests in plummer boxes at its ends, and is made to
revolve by any mechanical power. A certain quantity of plumbago or black
lead is put in along with the shot.
LAZULITE (Eng. and Fr.; _Lazulith_, Germ.); is a blue vitreous mineral,
crystallizing in rhomboidal dodecahedrons; spec. grav. 2·76 to 2·94;
scratches glass; affords a little water by calcination; fusible into a
white glass; dissolves in acids with loss of colour; solution leaves an
alkaline residuum, after being treated with carbonate of ammonia,
filtered, evaporated, and calcined. It consists of silica, 35·8;
alumina, 34·8; soda, 23·2; sulphur, 3·1; carbonate of lime, 3·1. This
beautiful stone affords the native _ultramarine_ pigment, which was very
costly till a mode of making it artificially was lately discovered. See
ULTRAMARINE.
LEATHER, (_Cuir_, Fr.; Germ., _Leder_); is the skin of animals, so
modified by chemical means as to have become unalterable by the external
agents which tend to decompose it in its natural state. The preparation
in a rude manner of this valuable substance, has been known from the
most antient times, but it was not till the end of the last, and the
beginning of the present century, that it began to be manufactured upon
right principles, in consequence of the researches of Macbride, Deyeux,
Seguin, and Davy. There are several varieties of leather; such as sole
leather, boot or upper leather, shamoy leather, kid or glove leather,
&c. Skins may be converted into leather either with or without their
hairy coat.
We shall treat first of sole and upper leathers, being the most
important, and most costly and difficult to prepare in a proper manner.
These kinds consist of organized fibrous gelatine or skin, combined with
the proximate vegetable principle, tannin, and probably also some
vegetable extractive. Under the articles GALLS and TANNIN, will be found
an account of the properties of this substance, and the means of
obtaining it in a state of purity. Calf leather quickly tanned by an
infusion of galls, consists of 61 parts of skin, and 39 of vegetable
matter in 100 by weight; by solution of catechu, it consists of 80 of
skin, and 20 of vegetable matter; by infusion of Leicester willow, of
74·5 skin, and 25·5 vegetable matter; and by infusion of oak bark, of
73·2 skin, and 26·8 vegetable matter. By the slow process of tanning,
continued for three months, the increase of weight upon the skin in its
conversion into leather, is greatly less; the vegetable constituents
being from Leicester willow only 13 per cent. of the leather, and from
oak bark 15 per cent. Sole leather, however, generally contains no less
than 40 per cent. of vegetable matter. In every astringent bark, the
inner white part next to the _alburnum_, contains the largest quantity
of tannin, and the middle coloured part contains most extractive matter.
The outer surface or epidermis seldom furnishes either tannin or
extractive matter. Young trees abound most in the white cortical layers,
and are hence more productive of tannin under equal weights, than the
barks of old trees. In no case is there any reason to believe that the
gallic acid of astringent vegetables is absorbed in the process of
making leather; hence Seguin’s theory of the agency of that substance in
disoxygenating skin, falls to the ground. The different qualities of
leather made with the same kind of skin, seem to depend very much upon
the different quantities of extractive matter it may have absorbed. The
leather made with infusion of galls, is generally harder and more liable
to crack than the leather obtained from infusions of barks; and it
always contains a much larger proportion of tannin, and a smaller
proportion of extractive matter.
When calf skin is slowly tanned in weak solutions of the bark, or of
catechu, it combines with a good deal of extractive matter, and though
the increase of the weight of the skin be comparatively small, yet it
has become perfectly insoluble in water, forming a soft, but at the same
time a strong leather. The saturated infusions of astringent barks
contain much less extractive matter in proportion to their tannin, than
the weak infusions; and when skin is quickly tanned in the former, it
produces a worse and less durable leather than when slowly tanned in the
latter. In quick tanning, a considerable quantity of vegetable
extractive matter is thus lost to the manufacturer, which might have
been made to enter as a useful constituent into the leather. These
observations show that there is sufficient foundation for the opinion of
the common workmen, concerning what is technically called _feeding_ of
leather, in the slow method of tanning; and though the processes of this
art have been unnecessarily protracted by defective methods of steeping,
and want of progressive infiltration of the astringent liquor through
the skins, yet in general they appear to have arrived, in consequence of
old experience, at a degree of perfection in the quality of the leather,
which cannot be far exceeded by means of any theoretical suggestions
which have been advanced.
On the first view it may appear surprising, that in those cases of quick
tanning, where extractive matter forms a certain portion of the leather,
the increase of weight is less than when the skin is combined with the
pure tannin; but the fact is easily accounted for, when we consider that
the attraction of skin for tannin must be probably weakened by its union
with extractive matter; and whether we suppose that the tannin and
extractive matter enter together into combination with the matter of
skin, or unite with separate portions of it, still, in either case, the
primary attraction of skin for tan must be to a certain extent
diminished.
In examining astringent vegetables in relation to their power of making
leather, it is necessary to take into account not only the quantity they
may contain of the _substance_ precipitable by gelatine, but likewise
the quantity and the nature of the extractive matter; and in cases of
comparison, it is essential to employ infusions of the same degree of
concentration.
Of all astringent substances hitherto examined, catechu is that which
contains the largest proportion of tannin; and in supposing, according
to the usual estimation, that from four to five pounds of common oak
bark are required to produce one pound of leather, it appears, from the
various synthetical experiments, that about half a pound of catechu
would answer the same purpose. Mr. Purkis found, by the results of
different accurate experiments, that 1 pound of catechu was equivalent
to 7 or 8 of oak bark. For the common purposes of the tanner, 1 pound of
it would be equivalent also to 2-1/4 pounds of galls, to 7-1/2 of the
Leicester willow, to 11 of the bark of the Spanish chesnut, to 18 of the
bark of the common elm, to 21 of the bark of the common willow, and to 3
pounds of sumach.
Various menstrua have been proposed for the purpose of expediting and
improving the process of tanning, among others, lime water, and solution
of pearl-ash; but as these two substances form compounds with tannin
which are not decomposable by gelatine, it follows that their effects
must be prejudicial. There is very little reason to suppose that any
bodies will be found which, at the same time that they increase the
solubility of tannin in water, will not likewise diminish its attraction
for skin.
In this country all tanned leather is distinguished into two kinds,
called _hides_ and _skins_; the former term being appropriated to that
made from the larger animals, as bulls, buffaloes, oxen, and cows, into
thick strong sole leather; and the latter to that made from calves,
seals, &c., into thinner and more flexible upper leather. Sometimes the
hides are brought into the market merely dried, as from Buenos-Ayres; or
dried and salted, as from Bahia and Pernambuco; but the greater part are
fresh from recently slaughtered animals. The heaviest ox hides are
preferred for forming _butts_ or _backs_, which are manufactured as
follows:--
The washing process must be more or less elaborate, according to the
state of the skins. Those that are salted and dry require to be steeped,
beaten, and rubbed several times alternately, to bring them to the fresh
condition.
After removing the horns, the softened or recent hides are laid in a
heap for two or three days, after which they are suspended on poles in a
close room called a smoke-house, heated somewhat above the common
temperature by a smouldering fire. In these circumstances, a slight
putrefaction supervenes, which loosens the epidermis, and renders the
hair easily detachable by the _fleshing_ knife; a large two-handled
implement, with a blunt edge, and bent to suit the curvature of the
rounded beam of the wooden horse upon which the hide is scraped. See
CURRYING.
The next step is immersion in a pit containing water impregnated with
about a 1000th part of sulphuric acid. This process is called _raising_,
because it distends the pores, and makes the fibres swell, so as to
render the skins more susceptible of the action of the tanning
infusions. Forty-eight hours in general suffice for this operation, but
more time may be safely taken.
When the hides are found to be sufficiently raised, they are transferred
to a pit, in which they are stratified with oak bark, ground by a proper
mill into a coarse powder. The pit is then filled up with an infusion of
oak bark called ooze, and the hides are allowed to remain in it for
about a month or six weeks. By this time the tannin and extractive
matter of the bark having combined intimately with the animal fibre, the
pit is exhausted of its virtue, and must be renewed, by taking out the
spent bark, and subjecting the skins to a fresh dose of oak bark and
ooze. The hides which were placed near the top of the first pit, must be
placed near the bottom of the next. In this mixture they remain, upon
the old practice, about three months. The last process being repeated
twice or thrice, perfectly tanned leather is the result. The hides are
now removed from the pit, and hung up in a shed. In the progress of
drying, which should be slow, they are compressed with a steel tool, and
beaten smooth, to render them more firm and dense.
Some manufacturers place on the bottom of the pit 5 or 6 inches of spent
bark, over it 2 inches of fresh bark, then a skin; and so, alternately,
a layer of new bark and a skin, till the pit is nearly full, reserving a
small space at top for a thicker layer of bark, over which weighted
boards are laid, to condense the whole down into the tanning infusion.
The operation of tanning sole leather in the above way, lasts a year or
a year and a half, according to the quality wanted, and the nature of
the hides.
A perfect leather is recognized by its section, which should have a
glistening marbled appearance, without any white streaks in the middle.
_Crop hides_ are manufactured by immersion, during three or four days,
in pits containing milk of lime; in which they are occasionally moved up
and down in order to expose them equally to the action of this
menstruum. They are then removed, and cleared from hair and impurities,
by using the fleshing knife upon the horse; after which they must be
completely freed from the lime by a thorough washing. They are next
plunged in pits containing a weak ooze or infusion of oak bark, from
which they are successively transferred into other pits with stronger
ooze; all the while being daily _handled_, that is, moved up and down in
the infusion. This practice is continued for about a month or six weeks.
They are now ready to be subjected to a mixture of ground oak bark and
stronger ooze in other pits, to a series of which they are progressively
subjected during two or three months.
The hides are next put into large vats, called _layers_, in which they
are smoothly stratified with more oak bark, and a stronger infusion of
it. After six weeks they are taken out of these vats, and subjected to a
new charge of the same materials for two months. This simple process is
repeated twice or thrice, at the option of the manufacturer, till the
hides are thoroughly tanned. They are then slowly dried, and condensed
in the manner above described. These crop hides form the principal part
of the sole leather used for home consumption in England.
The process of tanning _skins_ (as of calves, seals, &c.) is in some
respects peculiar. They are left in the lime pits for about twelve days,
when they are stripped of their hair, washed in water, then immersed in
a lixivium of pigeons’ dung, called a _grainer_, of an alkaline nature.
Here they remain from eight to ten days, according to the state of the
atmosphere, during which time they are frequently handled, and scraped
on both sides upon a convex wooden beam. This scraping or _working_, as
it is termed, joined to the action of the _grainer_, serves to separate
the lime, oil, and glutinous matter, and to render the skin pliant,
soft, and ready to imbibe the tanning principle. They are with this view
transferred into pits containing a weak solution of bark, in which they
undergo nearly the same treatment as described above for _crop_ hides;
but they are not commonly stratified in the layers. The time occupied in
tanning them is usually limited to three months. They are then dried,
and disposed of to the currier, who dresses and blackens them for the
upper leathers of boots and shoes, for harness, and other purposes. The
light and thin sorts of cow and horse hides are often treated like calf
skins.
In all the above processes, as the animal fibres on the surface of the
skin absorb most readily the tanning principles, and thereby obstruct,
in a certain degree, their passage into the interior fibres, especially
of thick hides, it becomes an object of importance to contrive some
method of overcoming that obstacle, and promoting the penetration of the
tan. The first manufacturer who appears to have employed efficacious
mechanical means of favouring the chemical action was Francis G.
Spilsbury, who in April, 1823, obtained a patent for the following
operation:--After the hides are freed from the hairs, &c. in the usual
way, they are minutely inspected as to their soundness, and if any holes
be found, they are carefully sewed up, so as to be water tight. Three
frames of wood are provided of equal dimensions, fitted to each other,
with the edges of the frames held together by screw bolts. A skin about
to be tanned is now laid upon the frame, and stretched over its edges,
then the second frame is to be placed upon it, so that the edges of the
two frames may pinch the skin all round and hold it securely; another
such skin is then stretched over the upper surface of the second frame,
in like manner, and a third frame being set upon this, confines the
second skin. The three frames are then pinched tightly together by a
series of screw bolts, passing through ears set round their outer edges,
which fix the skin in a proper manner for being operated upon by the
tanning liquor.
A space has been thus formed between the two skins, into which, when the
frames are set upright, the infusion is introduced by means of a pipe
from the cistern above, while the air is permitted to escape by a
stopcock below. This cock must of course be shut whenever the bag is
filled, but the one above is left open to maintain a communication with
the liquor cistern, and to allow the hydrostatic pressure to force the
liquor through the cutaneous pores by a slow infiltration, and thus to
bring the tannin into contact with all the fibres indiscriminately. The
action of this pressure is evinced by a constant perspiration on the
outer surfaces of the skins.
When the tanning is completed, the upper stopcock is closed, and the
under is opened to run off the liquor. The frames are now removed, the
bolts are unscrewed, and the pinched edges of the skins pared off; after
which they are to be dried and finished in the usual manner.
A modification of this ingenious and effectual process was made the
subject of a patent, by William Drake, of Bedminster, tanner, in
October, 1831. The hides, after the usual preparatory processes, are
immersed in a weak tan liquor, and by frequent handling or turning over,
receive an incipient tanning before being submitted to the infiltration
plan. Two hides, as nearly of the same size and shape as possible, are
placed grain to grain, when their corresponding edges are sewed firmly
together all round by shoemaker’s waxed thread, so as to form a bag
sufficiently tight to hold tan liquor. This bag must then be suspended
by means of loops sewed to its shoulder end, upon pegs, in such a manner
that it may hang within a wooden-barred rack, and be confined laterally
into a book form. About an inch of the bag is left unsewed at the upper
end, for the purpose of introducing a funnel through which the cold tan
liquor is poured into the bag till it be full. After a certain interval
which varies with the quality of the hides, the outer surface becomes
moist, and drops begin to form at the bottom of the bag. These are
received in a proper vessel, and when they accumulate sufficiently may
be poured back into the funnel; the bag being thus, as well as by a
fresh supply from above, kept constantly distended.
When the hides are observed to feel hard and firm, while every part of
them feels equally damp, the air of the tanning apartment having been
always well ventilated, is now to be heated by proper means to a
temperature gradually increasing from 70° to 150° of Fahrenheit’s scale.
This heat is to be maintained till the hides become firmer and harder in
all parts. When they begin to assume a black appearance in some parts,
and when the tan liquor undergoes little diminution, the hides may be
considered to be tanned, and the bag may be emptied by cutting a few
stitches at its bottom. The outer edges being pared off, the hides are
to be finished in the usual way. During their suspension within the
racks, the hides should be shifted a little sideways, to prevent the
formation of furrows by the bars, and to facilitate the equable action
of the liquor.
By this process the patentee says, that a hide may be tanned as
completely in ten days as it could be in ten months by the usual method.
I have seen a piece of sole leather thus rapidly tanned, and it seemed
to be perfect. How it may wear, compared with that made in the old way,
I cannot pretend to determine.
Messrs. Knowlys and Duesbury obtained a patent in August, 1826, for
accelerating the impregnation of skins with tannin, by suspending them
in a close vessel, from which the air is to be extracted by an air pump,
and then the tanning infusion is to be admitted. In this way, it is
supposed to penetrate the hide so effectually as to tan it uniformly in
a short time.
About 32 years ago, a similar vacuum scheme was employed to impregnate
with weaver’s paste or starch, the cops of cotton weft, for the dandy
looms of Messrs. Radcliff and Ross, of Stockport.
Danish leather is made by tanning lamb and kid skins with willow bark,
whence it derives an agreeable smell. It is chiefly worked up into
gloves.
_Of the tawing or dressing of skins for gloves, and white sheep
leather._
The operations of this art are: 1. washing the skins; 2. properly
treating them with lime; 3. taking off the fleece; 4. treatment in the
leather steep.
A shed erected upon the side of a stream, with a cistern of water for
washing the skins; wooden horses for cleaning them with the back of the
fleshing knife; pincers for removing the fibres of damaged wool; a
plunger for depressing the skins in the pits; a lime pit; a pole with a
bag tied to the end of it; a two-handed fleshing knife; a rolling pin,
from 15 to 18 inches long, thickened in the middle; such are some of the
utensils of a tawing establishment. There must be provided also a table
for applying the oil to the skins; a fulling mill, worked by a
water-wheel or other power; a dressing peg; a press for squeezing out
the fatty filth; a stove; planks mounted upon legs, for stretching the
skins, &c.
Fresh skins must be worked immediately after being washed, and then
dried, otherwise they ferment, and contract either indelible spots, or
get tender in certain points, so as to open up and tear under the tools.
When received in the dry state they should be steeped in water for two
days, and then treated as fresh skins. They are next strongly rubbed on
the convex horse-beam with a round-edged knife, in order to make them
pliant. The rough parts are removed by the fleshing knife. One workman
can in this way prepare 200 skins in a day.
The flesh side of each being rubbed with a cold cream of lime, the skins
are piled together with the woolly side of each pair outermost, and the
flesh sides in contact. They are left in this state for a few days, till
it is found that the wool may be easily removed by _plucking_.
They are next washed in running water, to separate the greater part of
the lime, stripped of the wool by small spring tweezers, and then
fleeced smooth by means of the rolling-pin, or sometimes by rubbing with
a whetstone. Unless they be fleeced soon after the treatment with lime,
they do not well admit of this operation subsequently, as they are apt
to get hard.
They are now steeped in the milk of lime-pit, in order to swell, soften,
and cleanse them; afterwards in a weak pit of old lime-water, from which
they are taken out and drained. This steeping and draining upon inclined
tables, are repeated frequently during the space of 3 weeks. Only the
skins of young animals, or those of inferior value are tawed. Sometimes
the wool is left on, as for housings, &c.
The skins, after having been well softened in the steeps, are rubbed on
the outside with a whetstone set in a wooden case with two handles, in
order to smooth them completely by removing any remaining filaments of
wool. Lamb skins are rubbed with the pin in the direction of their
breadth, to give them suppleness; but sheep skins are fulled with water
alone. They are now ready for the _branning_, which is done by mixing 40
lbs. of bran with 20 gallons of water, and keeping them in this
fermentable mixture for three weeks--with the addition, if possible, of
some old bran water. Here they must be frequently turned over, and
carefully watched, as it is a delicate operation. In the course of two
days in summer, and eight in winter, the skins are said to be _raised_,
when they sink in the water. On coming out of the bran, they are ready
for the white stuff; which is a bath composed of alum and sea-salt.
Twelve, fourteen, and sometimes eighteen pounds of alum for 100 skins,
form the basis of the bath; to which two and a half pounds of salt are
added in winter, and three in summer. These ingredients are introduced
into a copper with twelve gallons of water. The salt aids in the
whitening action. When the solution is about to boil, three gallons of
it are passed through the cullender into a basin; in this 26 skins are
worked one after another, and after draining, they are put together into
the bath, and left in it for ten minutes to imbibe the salts. They are
now ready to receive the paste. For 100 skins, from 13 to 15 pounds of
wheat flour are used along with the yolks of 50 eggs. After having
warmed the alum bath through which the skins have been passed, the
flower is dusted into it, with careful stirring. The paste is well
kneaded by the gradual addition of the solution, and passed through the
cullender, whereby it becomes as clear as honey. To this the yolks being
added, the whole is incorporated with much manual labour. The skins are
worked one after another in this paste; and afterwards the whole
together are left immersed in it for a day. They are now stretched and
dried upon poles, in a proper apartment, during from 8 to 15 days,
according to the season.
The effects of the paste are to whiten the skins, to soften them, and to
protect them from the hardening influence of the atmosphere, which would
naturally render them brittle. They would not bear working upon the
_softening iron_, but for the emulsion which has been introduced into
their substance. With this view they are dipped in a tub of clear water
during five or six minutes, and then spread and worked upon the board.
They are increased by this means in length, in the proportion of 5 to 3.
No hard points must be left in them. The whiteness is also better
brought out by this operation, which is performed upon the flesh side.
The softening tool is an iron plate, about one foot broad, rounded over
above, mounted upon an upright beam, 30 inches high, which is fixed to
the end of a strong horizontal plank, 3-1/2 feet long, and 1 broad. This
plank is heavily loaded, to make it immovable upon the floor. Sometimes
the skins are next spread over an undressed clean skin upon the horse,
and worked well with the two-handled knife, for the purpose of removing
the first and second epidermis, called the _fleur_ and _arrière-fleur_
by the French _megissiers_. They are then dried while stretched by hooks
and strings. When dry they are worked on the _stretching iron_, or they
are occasionally polished with pumice stone. A delicate yellow tint is
given by a composition made of two parts of whitening, and one of ochre,
applied in a moistened state, and well worked in upon the grain side.
After being polished with pumice, they are smoothed with a hot iron, as
the laundresses do linen, whereby they acquire a degree of lustre, and
are ready to be delivered to the _glover_.
For _housings_, the best sheepskins are selected, and such as are
covered with the longest and most beautiful fleece. They are steeped in
water, in order to be cleaned and softened; after which they are thinned
inside by the fleshing knife. They are now steeped in an old bran pit
for 3 or 4 days, when they are taken out and washed. They are next
subjected to the white or alum bath, the wool being carefully folded
within; about 18 pounds of alum being used for 100 skins. The paste is
made as for the fleeced skins, but it is merely spread upon their flesh
side, and left upon them for 18 hours, so as to stiffen. They are then
hung up to dry. They are next moistened by sprinkling cold water upon
them, folded up, piled in a heap, and covered with boards weighted with
heavy stones; in which state they remain for two days. They are next
opened with a round iron upon the horse, and subjected to the stretching
iron, being worked broadwise. They are dried with the fleece outermost,
in the sun if possible; and are finished upon the _stretcher_.
Calf and lamb skins with their hair and wool are worked nearly in the
same manner; only the thicker the skin, the stronger the alum bath ought
to be. One pound of alum and one of salt are required for a single calf
skin. It is left four days in this bath, after which it is worked upon
the _stretcher_, then fulled. When half dry the skins are opened upon
the horse. In eight days of ordinary weather, they may be completely
dressed. Lamb skins are sometimes steeped during eight days in a bath
prepared with unbolted rye flour and cold water, in which they are daily
moved about two or three times. They are then dried, stretched upon the
iron, and switched upon the fleecy side.
_Chamois_ or _Shamoy leather_.--The skins are first washed, limed,
fleeced, and branned as above described. They are next _efflowered_,
that is, deprived of their epidermis by a concave knife, blunt in its
middle part, upon the convex horse-beam. The cutting part serves to
remove all excrescences, and to equalize the thickness, while the blunt
part softens and smooths. The skins of goats, does, and chamois are
always treated in this way. They are next subjected to the fermenting
bran steep for one or two days, in ordinary weather; but in hot weather
for a much shorter time, sometimes only moving them in the sour bran
liquor for a few minutes. They are lastly wrung at the peg, and
subjected to the fulling mill.
When the skins have been sufficiently swelled and suppled by the
branning, they may receive the first oil as follows: a dozen skins being
stretched upon the table, the fingers are dipped in the oil, and shaken
over the skins in different places, so as to impart enough of it to
imbue the whole surface slightly, by friction with the palms of the
hands. It is to the outside or _grain_ that the oil is applied. The
skins are folded four together, so as to form balls of the size of a
hog’s bladder, and thrown into the trough of the fulling mill, to the
number of twelve dozen at once. Here they remain exposed to the beater
for two, three, or four hours, according to their nature and the state
of the weather. They are taken out, aired, oiled, and again fulled. The
airing and fulling are repeated several times, with more or less
frequent oilings. Any cheap animal oil is employed.
After these operations, the skins require to be subjected to a
fermenting process, to dilate their pores, and to facilitate their
combination with the oil. This is performed in a chamber only 6 feet
high, and 10 or 12 feet square. Poles are suspended horizontally a few
inches from the ceiling, with hooks fixed in them to which the skins are
attached. A somewhat elevated temperature is maintained, and by a stove
if need be. This operation requires great skill and experience.
The remainder of the epidermis is next removed by a blunt concave knife
and the horse; whereby the surface is not cut, but rather forcibly
scraped.
The skins are now scoured to carry off the redundant oil; which is
effected by a potash lye, at two degrees Baumé, heated no hotter than
the hand can bear. In this they are stirred briskly, steeped for an
hour, and lastly wrung at the peg. The soapy liquor thus expelled is
used for inferior purposes. The clean skins after being dried, are
finished first on the _stretcher-iron_, and then on the _herse_ or
stretching frame.
_Leather of Hungary._--This is manufactured by impregnating strong hides
with alum, common salt, and suet; by a rapid process which is usually
completed in the space of two months. The workshop is divided into two
parts; 1. a shed on the side of a stream, furnished with wooden horses,
fleshing knives, and other small tools. In one corner is a furnace with
a boiler for dissolving the alum, a vat for immersing the hides in the
solution, and several subsidiary tubs. 2. A chamber, 6 feet high, by 15
feet square, capable of being made very tight, for preserving the heat.
In one corner is a copper boiler, of sufficient size to contain 170
pounds of tallow. In the middle of the stove is a square stone slab,
upon which an iron grate is placed about a yard square. This is covered
with charcoal. At each side of the stove are large tables, which occupy
its whole length, and on which the leather is spread to receive the
grease. The upper part below the ceiling is filled with poles for
hanging the leather upon to be heated. The door is made to shut
perfectly close.
The first operations are analogous to those of tanning and tawing; the
skins being washed, cut in halves, shaved, and steeped for 24 hours in
the river. They are then cleaned with 5 or 6 pounds of alum, and 3-1/2
pounds of salt, for a piece of hide which weighs from 70 to 80 pounds.
The common salt softens the effect of the alum, attracts the moisture of
the air, and preserves the suppleness of the skin. When the alum and
salt are dissolved, hot water is poured upon the hides placed in a vat,
and they are tramped upon by a workman walking repeatedly from one end
of the vat to the other. They are then transferred into a similar vat
containing some hot water, and similarly tramped upon. They are next
steeped for eight days in alum water. The same round of operations is
repeated a second time.
The skins are now dried either in the air, or a stove room; but before
being quite dry, they are doubled together, well stretched to take out
the wrinkles, and piled up. When dry, they are again tramped to open the
pores as well as to render the skin pliant, after which they are
whitened by exposure to the sun.
Tallow of inferior quality is employed for greasing the leather. With
this view the hides are hung upon the poles in the close stove room,
then laid upon the table, and besmeared with the tallow melted till it
begins to crackle. This piece is laid on another table, is there covered
with a second, similarly greased, and so forth. Three pounds of fat are
commonly employed for one piece of leather.
When the thirty strips, or fifteen hides passed through the grease in
one operation are completed, two workmen take the first piece in their
hands, and stretch it over the burning charcoal on the grate for a
minute, with the flesh side to the fire. The rest are passed over the
flame in like manner. After _flaming_, the pieces are successively laid
on an inclined table exposed to the fire, where they are covered with a
cloth. They are finally hung upon poles in the air to dry; and if the
weather be warm, they are suspended only during the night, so as to
favour the hardening of the grease. Instead of the alum bath, M.
Curaudau has employed with advantage a steep of dilute sulphuric acid.
_Morocco leather._--The true morocco leather is goat skin tanned and
then dyed on the side of the grain. Sheep skins are treated in the same
way. The skins are steeped first in a fermenting mixture of bran water
for a few days, they are then worked upon the horse, steeped in fresh
water for 12 hours, and rinsed in the same. They are next drained,
steeped in weak lime pits for a proper time, till the hairs can be
readily detached. They are now subjected to the action of a blunt knife
upon the horse-beam, in order to strip off their hair, after which they
are cleansed in running water. Any excrescences must be carefully
removed with the fleshing knife, and their edges neatly pared. The next
process is rubbing them strongly with a piece of hard schist, set in a
wooden frame, in order to expel by the pressure any lime which may still
adhere, and to soften the grain. They are now worked upon the horse-beam
with the blunt knife, and subjected to a species of fulling, by being
agitated by pegs in a revolving cask along with water. Many
manufacturers prefer a weak alkaline lye, or putrified urine, to the
lime bath.
The skins are immersed for a night and a day, in a bran bath, in a
certain state of fermentation, then worked on the horse, and salted, to
preserve them till they are to be dyed.
Preparatory to being dyed, each skin is sewed together edgewise, with
the grain on the outside, and it is then mordanted either with a
solution of tin, or with alum water. The colour is given by cochineal,
of which from 10 to 12 ounces are required for a dozen of skins. The
cochineal being boiled in water along with a little tartar or alum for a
few minutes, forms a red liquor, which is filtered through a linen
cloth, and put into a clean cask. The skins are immersed in this bath,
and agitated in it for about half an hour; they are taken out and
beaten, and then subjected to a second immersion in the cochineal bath.
After being thus dyed, they are rinsed and tanned with Sicilian sumach,
at the rate of two pounds for a skin of moderate size. This process is
performed in a large tub made of white wood, in the liquor of which the
skins are floated like so many bladders, and moved about by manual
labour during four hours. They are then taken out, drained, and again
subjected to the tanning liquor; the whole process requiring a space of
twenty-four hours. The skins are now unstitched, rinsed, fulled with
beetles, drained, rubbed hard with a copper blade, and lastly hung up to
dry.
Some manufacturers brighten the colour by applying to the surface of the
skins, in a damp state, a solution of carmine in ammonia with a sponge;
others apply a decoction of saffron to enliven the scarlet tint. At
Paris the morocco leather is tanned by agitation with a decoction of
sumach in large casks made to revolve upon a horizontal axis, like a
barrel churn. White galls are sometimes substituted for sumach; a pound
being used for a skin. The skins must be finally cleaned with the utmost
care.
The black dye is given by applying with the brush a solution of red
acetate of iron to the grain side. Blue is communicated by the common
cold indigo vat; violets, with a light blue followed by cochineal red;
green, by Saxon blue followed by a yellow dye, usually made with the
chopped roots of the barberry. This plant serves also for yellows. To
dye olive, the skins are first passed through a weak solution of green
vitriol, and then through the decoction of barberry root, containing a
little Saxon blue. Puce colour is communicated by logwood with a little
alum; which may be modified by the addition of a little Brazil wood. In
all these cases, whenever the skins are dyed, they should be rinsed,
wrung or rather drained, stretched upon a table, then besmeared on the
grain side with a film of linseed oil applied by means of a sponge, in
order to promote their glossiness when curried, and to prevent them
becoming horny by too rapid drying.
The last process in preparing morocco leather is the currying, which
brings out the lustre, and restores the original suppleness. This
operation is practised in different manners, according to the purpose
the skins are to serve. For pocket-books, portfolios, and case-making in
general, they must be thinned as much as possible upon the flesh side,
moistened slightly, then stretched upon the table, to smooth them; dried
again, moistened, and lastly passed two or three times through the
cylinder press in different directions, to produce the crossing of the
grain. The skins intended for the shoemaker, the saddler, the
bookbinder, &c., require more pliancy, and must be differently curried.
After being thinned, they are glazed with a polisher while still moist,
and a grain is formed upon the flesh side with the roughened lead plate
or grainer of the curriers, called in French _pommelle_; they are glazed
anew to remove the roughness produced by the pommel, and finally grained
on the flesh side with a surface of cork applied under a pommel of white
wood.
_Russia leather._--The Russians have long been possessed of a method of
making a peculiar leather, called by them _jucten_, dyed red with the
aromatic saunders wood. This article has been much sought after, on
account of not being subject to mould in damp situations, being proof
against insects, and even repelling them from the vicinity of its odour.
The skins are freed from the hair or fleece, by steeping in an ash-lye
too weak to act upon the animal fibres. They are then rinsed, fulled for
a longer or shorter time according to their nature, and fermented in a
proper steep, after having been washed in hot water. They are taken out
at the end of a week, but they may be steeped a second time if deemed
necessary, to open their pores. They are now cleaned by working them at
the horse on both the flesh and grain sides.
A paste is next composed, for 200 skins, of 38 pounds of rye flour,
which is set to ferment with leaven. This dough is worked up with a
sufficient quantity of water to form a bath for the skins, in which they
are soaked for 48 hours; they are then transferred into small tubs,
where they remain during fifteen days, after which they are washed at
the river. These operations serve to prepare the skins for absorbing the
astringent juices with uniformity. A decoction of willow bark (_salix
cinerea_, and _salix caprea_) being made, the skins are immersed in the
boiler whenever the temperature of the liquor is sufficiently lowered
not to injure the animal fibres, and handled and pressed for half an
hour. This manipulation is repeated twice daily during the period of a
week. The tanning infusion is then renewed, and applied to the same
skins for another week; after which being exposed to the air to dry,
they are ready for being dyed, and then curried with the empyreumatic
oil of the bark of the birch tree. To this substance the Russia leather
owes its peculiarities. Many modes have been prescribed for preparing
it; but the following is the one practised in Russia.
The whitish membranous epidermis of the birch, stripped of all woody
parts, is introduced into an iron boiler, which, when stuffed full, is
covered tight with a vaulted iron lid, having a pipe rising from its
centre. A second boiler into which this pipe passes without reaching its
bottom, is set over the first, and is luted to it at the edges, after
the two are bolted together. They are then inverted, so that the upper
one contains the birch bark. The under half of this apparatus is sunk in
the earth, the surface of the upper boiler is coated over with a clay
lute, then surrounded with a fire of wood, and exposed to a red heat,
till the distillation be completed. This operation, though rude in
appearance, and wasteful of wood, answers its purpose perfectly well.
The iron cylinder apparatus used in Britain for distilling wood vinegar,
would, however, be much more convenient and productive. When the above
boilers are unluted, there is found in the upper one a very light powder
of charcoal, and in the under one which served as a receiver, there is
an oily, brown, empyreumatic fluid, of a very strong smell, which is
mixed with the tar, and which floats over a small quantity of crude
vinegar. The former matter is the oil employed to impregnate the skins,
by working it into the flesh side with the curriers’ tools. It is
difficult to make this oil penetrate with uniformity; and the Russians
do not always succeed in this process, for they turn out many skins in a
spotted state. This oil is at present obtained in France by distilling
the birch bark in copper stills, and condensing the products by means of
a pipe plunged in cold water. About 60 per cent. of the weight of the
bark is extracted.
The skins imbibe this oil most equally before they are fully dry. Care
must be taken not to apply too much of it, for fear of its passing
through and staining the grain-side of the leather. Chevreul has
investigated the chemical nature of this odoriferous substance, and
finding it to be a peculiar compound, has called it _betuline_.
LEDUM PALUSTRE. This plant is employed in Russia to tan the skins of
goats, calves, and sheep, into a reddish leather of an agreeable smell;
as also in the preparation of the oil of birch, for making what is
commonly called Russia leather.
LEGUMINE, is the name of a vegeto-alkali supposed to exist in leguminous
plants.
LEMONS. See CITRIC ACID, and OILS, ESSENTIAL.
LEVIGATION, is the mechanical process whereby hard substances are
reduced to a very fine powder.
LEUCITE, is a hard Vesuvian mineral, consisting of silica, 54; alumina,
23; potash, 23.
LEUCINE, is a white crystalline substance produced by acting upon flesh
with sulphuric acid.
LEWIS, is the name of one kind of shears used in cropping woollen cloth.
LIAS, is a fine-grained argillaceous limestone, whose geological
position is under the oolite; it is the proper lithographic stone.
LIBAVIUS, LIQUOR OF, is the bichloride of tin, prepared by dissolving
that metal with the aid of heat, in _aqua regia_, or by passing chlorine
gas through a solution of muriate of tin till no more gas be absorbed,
evaporating the solution, and setting it aside to crystallize. The
anhydrous bichloride is best prepared by mixing four parts of corrosive
sublimate with one part of tin, previously amalgamated with just so much
mercury as to render it pulverizable; and by distilling this mixture
with a gentle heat. A colourless fluid, the dry bichloride of tin, or
the proper fuming liquor of Libavius, comes over. When it is mixed with
one-third of its weight of water it becomes solid. The first bichloride
of tin is used in calico-printing.
LICHEN. See ARCHIL.
LIGNEOUS MATTER, is vegetable fibre. See FIBROUS MATTER.
LIGNITE, is one of the most recent geological formations, being the
carbonaceous remains of forest trees. From this substance, as found in
the neighbourhood of Cologne, the brown colours, called _umber_ and
_earth of Cologne_, are prepared.
LILAC DYE. See CALICO-PRINTING AND DYEING.
LIMESTONE (_Calcaire_, Fr.; _Kalkstein_, Germ.); may be classed under
the following heads:--
1. _Calcareous spar_ occurs in colourless crystals or crystalline
masses; dissolves with effervescence in muriatic acid; is scratched by
soft iron, but not by the nail; specific gravity 2·7; loses 46 per cent.
by the expulsion of carbonic acid, and calcines into quicklime.
2. _Calcsinter_, _or stalactitic carbonate of lime_, called also
concretionary limestone, because formed of zones more or less undulated,
and nearly parallel. These zones have a fibrous structure, arising from
the successive deposits of the crystalline limestone from its solvent
water. The long conical pieces called stalactites, show fibres
converging to the axis. The tubercular consists of irregular lumps often
sprinkled over with small crystals, and associated so as to exhibit the
appearance of cauliflower. The stratiform, commonly called stalagmite,
or alabaster limestone, represents zones not concentric, but spread out,
waving, and parallel; its texture is sometimes lamellar, and sometimes
fibrous. These waving strata are distinguishable from one another by
their different densities, and by their degrees of translucency. This
stalagmitic mass bears the name of oriental alabaster, when it is
reddish-yellow with distinct zones, and is susceptible of a fine polish.
Stalactites are formed in the large excavations of calcareous rocks. The
water percolating down through them, and dropping from the roofs of the
caverns, is usually charged with carbonate of lime held in suspension by
an excess of carbonic acid. The exposure to air, the motion, and the
consequent diminution of pressure, cause the precipitation of the
carbonate of lime in the solid state. Each drop of water, on falling
through the vault, abandons a small film of limestone, which enlarges by
degrees, and forms either a cylinder or solid mass. This alabaster
differs from marble in its parallel and waving layers, and its faint
degree of transparency.
This alabaster serves for the decoration of public buildings, and is
occasionally introduced into certain pieces of furniture. The fine
Egyptian alabaster was anciently brought from the mountains of the
Thebaid, between the Nile and the Red Sea, near a town called
Alabastron, whence probably the name. Very fine red alabaster, of great
hardness, was found at one time in the quarries of Montmartre, but the
stock was soon exhausted.
_The incrusting concretionary limestone_ differs little from the
preceding except in the rapidity of its formation, and in being moulded
upon some body whose shape it assumes. These deposits from calcareous
springs, form equally on vegetable bodies, on stones, metals, within
pipes of cast iron, wood, or lead. The incrustations on vegetable and
animal substances are vulgarly called petrifactions, as the organic
fibres are replaced by stone. One of the most curious springs of this
nature is at the baths of Saint Philip, in Tuscany, where the water
flows in almost a boiling state, over an enormous mass of alabaster
which it has produced. The carbonate of lime seems to be held in
solution here by sulphuretted hydrogen, which flies off when the water
issues to the day. Dr. Vegny has taken advantage of this property of the
spring, to obtain basso-relievo figures of great whiteness and solidity.
He makes use of sulphur moulds.
_Calcareous tuf_ consists of similar incrustations made by petrifying
rivulets running over mud, sand, vegetable remains, &c. It is porous,
even cellular, somewhat soft, impure, and of a dirty gray colour. Its
surface is wavy, rough, and irregular. These incrustations or deposits
are, however, sometimes so abundant, and the resulting stony matters so
hard that buildings may be constructed with them. The stone with which
the town of Pasti, in Italy, is built has been called _pipe-stone_ by
the Italians; and it has apparently derived its origin from
incrustations upon large reeds.
The _travertino_, which served to construct all the monuments of Rome,
appears to have been formed by the deposits of the Anio and the
solfatara of Tivoli. The temples of Pæstum, which are of extreme
antiquity, have been built with a _travertino_ formed by the sediment of
the waters which still flow in this territory. All these stones acquire
great hardness in the air, and M. de Breislak thinks that it is to the
happy union of travertino and pouzzolana in the same spot, that the
monuments of Rome owe their great solidity.
_Spongy limestone_, usually called _Agaric mineral_, stone marrow, &c.,
belongs to this kind of formation. It has a very white colour, a very
fine grain, is soft to the touch, very tender, and light enough to float
for an instant on water. It occurs in rather thin layers, in the
crevices of calcareous rocks, and is so common in Switzerland as to be
employed for whitening houses.
3. _Compact limestone_, is of a grain more or less fine, does not
polish, nor afford large blocks free from fissures, has a conchoidal, or
uneven scaly fracture. Colours very various. Its varieties are; _a_, The
_sub-lamellar_, compact, with some appearance of a foliated texture.
_b_, _Compact fine-grained limestone_, the zechstein of the Germans, to
which M. Brongniart refers the lithographic stone in his classification
of rocks (_Dictionnaire des Sciences Naturelles_,) but the English
geologists place the locality of the famous lithographic quarry of
Solenhofen much higher in the plane of secondary superposition. Its
fracture is conchoidal; colour from gray to whitish; _c_, _Compact
common limestone_. Grain of middle size; earthy aspect; uneven fracture;
perfectly opaque; colour, whitish to pale gray, yellow, or reddish. The
limestones of the Jura formation are referred to this head, as well as
most of those interspersed among the coal strata. _d_, The _coarse
compact_, or Cornbrash; texture somewhat open, earthy aspect, rough to
the touch, ragged fracture, colour yellow, gray, or dirty red. _e_,
_Compact cellular_, the Rauchekalk and Holekalk of the Germans, on
account of the numerous holes or caverns distributed through it.
4. _Oolite or roe-stone._--It consists of spherical grains of various
size, from a millet seed, to a pea, or even an egg; texture compact;
fracture even; colours, whitish, yellow, gray, reddish, brownish. The
larger balls have almost always a foreign body for their centre or
nucleus.
5. _Chalk_; texture earthy; grains fine, tender, friable; colours white,
grayish, or pale yellowish.
6. _Coarse-grained limestone_; an earthy texture, in large particles,
often loose; fracture foliated, uneven; colour pale and dirty yellow.
Coarse lias has has been referred to this head.
7. _Marly limestone_; lake and fresh-water limestone formation; texture
fine-grained, more or less dense; apt to crumble down in the air; colour
white or pale yellow; fracture rough-grained, sometimes conchoidal;
somewhat tenacious. Texture occasionally cavernous; with cylindrical
winding cavities. This true limestone must not be confounded with the
lime-marl, composed of calcareous matter and clay.
8. _Siliceous limestone_; of a compact texture; scratching steel, and
scratched by it; leaves a siliceous residuum after the action of
muriatic acid.
9. _Calp_; texture compact; fine-grained; schistose structure; hard, as
the preceding; not burning into quicklime, affording to dilute muriatic
acid a copious residuum of clay and silica; colour blackish; found in
beds in the transition district near Dublin.
10. _Lucullite_ or stinkstone; texture compact or sub-lamellar, colour
grayish; emits the smell of sulphuretted hydrogen by friction or a blow.
It occurs at Assynt, in Sutherlandshire; in Derbyshire; counties of
Kilkenny, Cork, and Galway.
11. _Bituminous limestone_; black or blackish colour; diffusing by the
action of fire a bituminous odour, and becoming white.
Of all common limestones the purity may most readily be determined by
the quantity of carbonic acid which is evolved during their solution in
dilute nitric or muriatic acid. Perfect carbonate of lime loses in this
way 46 _per cent._; and if any particular limestone loses only 23 _per
cent._, we may infer that it contains only one half its weight of
calcareous carbonate. This method is equally applicable to _marls_,
which are mixtures in various proportions of carbonate of lime, clay,
and sand, and may all be recognized by their effervescing with acids.
The chief use of calcareous stones is for procuring quicklime by
calcination in proper furnaces; and they are all adapted to this purpose
provided they are not mixed with too large a proportion of sand and
ferruginous clay, whereby they acquire a vitrescent texture in a high
heat, and will not burn into lime. Limestone used to be calcined in a
very rude kiln, formed by enclosing a circular space of 10 or 15 feet
diameter, by rude stone walls 4 or 5 feet high, and filling the
cylindrical cavity with alternate layers of turf or coal and limestone
broken into moderate pieces. A bed of brushwood was usually placed at
the bottom, to facilitate the kindling of the kiln. Whenever the
combustion was fairly commenced, the top, piled into a conical form, was
covered in with sods, to render the calcination slow and regular. This
method being found relatively inconvenient and ineffectual, was
succeeded by a permanent kiln built of stones or brickwork, in the shape
of a truncated cone with the narrow end undermost, and closed at bottom
by an iron grate. Into this kiln, the fuel and limestone were introduced
at the top in alternate layers, beginning of course with the former; and
the charge was either allowed to burn out, when the lime was altogether
removed at a door near the bottom, or the kiln was successively fed with
fresh materials, in alternate beds, as the former supply sunk down by
the calcination, while the thoroughly burnt lime at the bottom was
successively raked out by a side door immediately above the grate. The
interior of the lime kiln has been changed of late years from the
conical to the elliptical form; and probably the best is that of an egg
placed with its narrow end undermost, and truncated both above and
below; the ground plot or bottom of the kiln being compressed so as to
give an elliptical section, with an _eye_ or draft-hole towards each end
of that ellipse. A kiln thus arched in above gives a reverberatory heat
to the upper materials, and also favours their falling freely down in
proportion as the finished lime is raked out below; advantages which
the conical form does not afford. The size of the draft-notes for
extracting the quicklime, should be proportionate to the size of the
kiln, in order to admit a sufficient current of air to ascend with the
smoke and flame, which is found to facilitate the extrication of the
carbonic acid. The kilns are called _perpetual_, because the operation
is carried on continuously as long as the building lasts; and
_draw-kilns_, from the mode of discharging them by raking out the lime
into carts placed against the draft-holes. Three bushels of calcined
limestone, or lime-shells, are produced on an average for every bushel
of coals consumed. Such kilns should be built up against the face of a
cliff, so that easy access may be gained to the mouth for charging, by
making a sloping cart road to the top of the bank.
[Illustration: 638 639 640 641]
_Figs._ 638, 639, 640, 641. represent the _lime-kiln_ of Rüdersdorf near
Berlin, upon the continuous plan, excellently constructed for
economizing fuel. It is triple, and yields a threefold product. _Fig._
640. is a view of it as seen from above; _fig._ 641., the elevation and
general appearance of one side; _fig._ 638, a vertical section, and
_fig._ 639. the ground plan in the line A B C D of _fig._ 638. The inner
shaft _fig._ 638. has the form of two truncated cones, with their larger
circular ends applied to each other; it has the greatest width at the
level of the fire-door _b_, where it is 8 feet in diameter; it is
narrower below at the discharge door, and at the top orifice, where it
is about 6 feet in diameter. The interior wall _d_, of the upper shaft
is built with hewn stones, to the height of 38 feet, and below that for
25 feet, with fire-bricks _d´ d´_, laid stepwise. This inner wall is
surrounded with a mantle _e_, of limestones, but between the two there
is a small vacant space of a few inches filled with ashes, in order to
allow of the expansion of the interior with heat taking place without
shattering the mass of the building.
The fire-grate _b_, consists of fire-tiles, which at the middle, where
the single pieces press together, lie upon an arched support _f_. The
fire-door is also arched, and is secured by fire-tiles. _g_ is the iron
door in front of that orifice. The tiles which form the grate have 3 or
4 slits of an inch wide for admitting the air, which enters through the
canal _h_. The under part of the shaft from the fire to the hearth, is 7
feet, and the outer enclosing wall is constructed of limestone, the
lining being of fire-bricks. Here are the ash-pit _i_, the discharge
outlet _a_, and the canal _k_, in front of the outlet. Each ash-pit is
shut with an iron door, which is opened only when the space _i_ becomes
filled with ashes. These indeed are allowed to remain till they get
cool enough to be removed without inconvenience.
The discharge outlets are also furnished with iron doors, which are
opened only for taking out the lime, and are carefully luted with loam
during the burning. The outer walls _l m n_ of the kiln, are not
essentially necessary, but convenient, because they afford room for the
lime to lie in the lower floor, and the fuel in the second. The several
stories are formed of groined arches _o_, and platforms _p_, covered
over with limestone slabs. In the third and fourth stories the workmen
lodge at night. See _fig._ 641. Some enter their apartments by the upper
door _q_; others by the lower door _s_. _r_ is one of the chimneys for
the several fire-places of the workmen. _t u v_ are stairs.
As the limestone is introduced at top, the mouth of the kiln is
surrounded with a strong iron balustrade to prevent the danger of the
people tumbling in. The platform is laid with rails _w_, for the waggons
of limestone, drawn by horses, to run upon. _x_ is another rail-way,
leading to another kiln. Such kilns are named after the number of their
fire-doors, single, twofold, threefold, fourfold, &c.; from three to
five being the most usual. The outer form of the kiln also is determined
by the number of the furnaces; being a truncated pyramid of equal sides;
and in the middle of each alternate side there is a fire-place, and a
discharge outlet. A cubic foot of limestone requires for burning, one
and five-twelfths of a cubic foot of wood, and one and a half of turf.
When the kiln is to be set in action, it is filled with rough
limestones, to the height C D, or to the level of the firing; a wood
fire is kindled in _a_, and kept up till the lime is calcined. Upon this
mass of quicklime, a fresh quantity of limestones is introduced, not
thrown in at the mouth, but let down in buckets, till the kiln be quite
full; while over the top a cone of limestones is piled up, about 4 feet
high. A turf-fire is now kindled in the furnaces _b_. Whenever the upper
stones are well calcined, the lime under the fire-level is taken out,
the superior column falls in, a new cone is piled up, and the process
goes on thus without interruption, and without the necessity of once
putting a fire into _a_; for in the space C B, the lime must be always
well calcined. The discharge of lime takes place every 12 hours, and it
amounts at each time in a threefold kiln, to from 20 to 24 Prussian
_tonnes_ of 6 imperial bushels each; or to 130 bushels imperial upon the
average. It is found by experience, that fresh-broken limestone which
contains a little moisture, calcines more readily than what has been
dried by exposure for some time to the air; in consequence of the vapour
of water promoting the escape of the carbonic acid gas; a fact well
exemplified in distilling essential oils, as oil of turpentine and
naphtha, which come over with the steam of water, at upwards of 100
degrees F. below their natural term of ebullition. Six bushels of
Rüdersdorf quicklime weigh from 280 to 306 pounds.
When coals are used for fuel in a well-constructed perpetual, or draw
kiln, about 1 measure of them should suffice for 4 or 5 of limestone.
The most extensive employment of quicklime is in agriculture, on which
subject instructive details are given in Loudon’s Encyclopædias of
Agriculture and Gardening.
Quicklime is employed in a multitude of preparations subservient to the
arts; for clarifying the juice of the sugar-cane and the beet-root; for
purifying coal gas; for rendering the potash and soda of commerce
caustic in the soap manufacture, and in the bleaching of linen and
cotton; for purifying animal matters before dissolving out their
gelatine; for clearing hides of their hair in tanneries; for extracting
the pure volatile alkali from muriate or sulphate of ammonia; for
rendering confined portions of air very dry; for stopping the leakage of
stone reservoirs, when mixed with clay and thrown into the water; for
making a powerful lute with white of egg or serum of blood; for
preparing a depilatory pommade with sulphuret of arsenic, &c. Lime water
is used in medicine, and quicklime is of general use in chemical
researches. Next to agriculture the most extensive application of
quicklime is to MORTAR-CEMENTS, which see.
LINEN. See FLAX, and TEXTILE FABRICS.
LINSEED (_Graine de lin_, Fr.; _Leinsame_, Germ.); contains in its dry
state, 11·265 of oil; 0·146 of wax; 2·488 of a soft resin; 0·550 of a
colouring resinous matter; 0·926 of a yellowish substance analogous to
tannin; 6·154 of gum; 15·12 of vegetable mucilage; 1·48 of starch; 2·932
of gluten; 2·782 of albumine; 10·884 of saccharine extractive; 44·382 of
envelopes, including some vegetable mucilage. It contains also free
acetic acid; some acetate, sulphate, and muriate of potash, phosphate
and sulphate of lime; phosphate of magnesia; and silica. See OILS,
UNCTUOUS.
LIQUATION (Eng. and Fr.; _Saigerung_, Germ.); is the process of sweating
out, by a regulated heat, from an alloy, an easily fusible metal from
the interstices of a metal difficult of fusion. Lead and antimony are
the metals most commonly subjected to liquation; the former for the
purpose of carrying off by a superior affinity the silver present in any
complex alloy, a subject discussed under SILVER; the latter will be
considered here, as referred to from the article ANTIMONY.
[Illustration: 642 643 644]
_Figs._ 642, 643, 644. represent the celebrated antimonial liquation
furnaces of Malbosc, in the department of Ardèche, in France. _Fig._
642. is a ground plan taken at the level of the draught holes _g g_,
_fig._ 643., and of the dotted line E F; _fig._ 643. is a vertical
section through the dotted line A B, of _fig._ 642.; and _fig._ 644. is
a vertical section through the dotted line C D of _fig._ 642. In the
three figures, the same letters denote like objects, _a b c_ are three
grates upon the same level above the floor of the works, 4-1/2 feet
long, by 10-1/2 inches broad; between which are two rectangular
galleries, _d e_, which pass transversely through the whole furnace, and
lie at a level of 12 inches above the ground. They are separated by two
walls from the three fire places. The walls have three openings, _f g
h_, alternately placed for the flames to play through. The ends of these
galleries are shut in with iron doors _i i_, containing peep holes. In
each gallery are two conical cast-iron crucibles _k k_, into which the
_eliquating_ sulphuret of antimony drops. Their height is from 12 to 14
inches, the width of the mouth is 10 inches, that of the bottom is 6,
and the thickness four-tenths of an inch. They are coated over with fire
clay, to prevent the sulphuret from acting upon them; and they stand
upon cast-iron pedestals with projecting ears, to facilitate their
removal from the gallery or platform. Both of these galleries are lined
with tiles of fire-clay _l l_, which also serve as supports to the
vertical liquation tubes _m m_, made of the same clay. The tiles are
somewhat curved towards the middle, for the purpose of receiving the
lower ends of these tubes, and have a small hole at _n_, through which
the liquid sulphuret flows down into the crucible.
The liquation tubes are conical, the internal diameter at top being 10
inches, at bottom 8; the length fully 40 inches, and the thickness
six-tenths of an inch. They have at their lower ends notches or slits
_o_, _fig._ 644., from 3 to 5 inches long, which look outwards, to make
them accessible from the front and back part of the furnaces through
small conical openings _p p_, in the walls. These are closed during the
operation with clay stoppers, and are opened only when the gangue,
rubbish, and cinders are to be raked out. The liquation tubes pass
across the arch of the furnace _q q_, the space of the arch being wider
than the tubes; they are shut in at top with fire-covers _r r_. _s s_,
the middle part of the arch, immediately under the middle grate, is
barrel-shaped, so that both arches are abutted together. The flames,
after playing round about the sides of the liquation tubes, pass off
through three openings and flues into the chimney _t_, about 13 feet
high; _u_ being the one opening, and _v_ the two others, which are
provided with register plates. In front of the furnace is a smoke flue
_w_, to carry off the sulphureous vapours exhaled during the clearing
out of the rubbish and slag; another _x_, begins over _y y_, at the top
of the tubes; a wall _z_, separates the smoke flue into halves, so that
the workmen upon the one side may not be incommoded by the fumes of the
other. This wall connects at the same time the front flue _w_ with the
chimney _t_. _a´ a´_ and _b´ b´_ are iron and wooden bearer beams and
rods for strengthening the smoke-flue, _c´ c´_ are arches upon both
sides of the furnace, which become narrower from without inwards, and
are closed with well-fitted plates _d´ d´_. They serve, in particular
circumstances, to allow the interior to be inspected, and to see if
either of the liquation furnaces be out of order.
Each tube being charged with about 500 lbs. of the antimonial ore,
previously warmed upon the roof of the furnace, in a short time the
sulphuret of a blue colour begins to flow out. Whenever the liquation
ceases, the cinders are raked out by the side openings, and the tubes
are charged afresh. The luted iron crucibles are suffered to become
three-fourths full, are then drawn out from the galleries, left to cool,
and emptied. The ingots weigh about 85 pounds. The charging is renewed
every three hours, and, when the process is in good train, 100 lbs. of
sulphuret of antimony are obtained every hour. The average duration of
the tubes is 3 weeks, though in some cases it may be 40 days. The
product from the ore is from 40 to 50 per cent. The above plan of
operation is remarkable for the small consumption of fuel, the economy
of labour, and the complete exhaustion of the ore.
LIQUEURS, LIQUORISTE; names given by the French to liquors compounded of
alcohol, water, sugar, and different aromatic substances; and to the
person who compounds them. I shall insert here a few of their most
approved recipes.
_Infusion of the peels of fruits._--The outer skin pared off with a
sharp knife, is to be dropped into a hard glazed jar, containing alcohol
of 34° B., diluted with half its bulk of water, and the whole is to be
transferred into well-corked carboys. After an infusion of six weeks,
with occasional agitation, the aromatized spirit is to be distilled off.
In this way are prepared the liquors of cedrat, lemons, oranges,
_limettes_ (a sort of sweet lemon), _poncires_ (the large citron),
bergamots, &c.
_Infusion of aromatic seeds._--These must be pounded, put into a carboy,
along with alcohol diluted as above, infused with agitation for six
weeks, and then distilled.
_Infusions of aromatic woods_ are made in the same way.
The liquorist should not bring his infusions and tinctures into the
market till six months after their distillation.
Liqueurs have different titles, according to their mode of fabrication.
Thus _waters_ are liquors apparently devoid of viscidity; _creams_ and
_oils_ possess it in a high degree.
Water of _cedrat_, is made by dissolving six pounds of sugar in seven
quarts of water; adding two quarts of spirit of _cedrat_, and one of
spirit of citron. Boil the whole for a minute, and filter hot through a
proper bag. Set it for a considerable time aside in a corked carboy,
before it be bottled.
_Oil or cream of cedrat._--Take eight quarts of river water, two of
spirit of cedrat, one of spirit of citron, and as much rich syrup as is
necessary to give the mixture an oily consistence. Stir it well and set
it aside in carboys. Should it be at all clouded, it must be filtered
till it be perfectly pellucid.
_Balm of Molucca_, is made by infusing for ten days, in a carboy capable
of holding fully four gallons, 10 pounds of spirits of 18° B., 4 pounds
of white sugar, 4 pounds of river water, 4 drachms of pounded cloves,
and 48 grains of pounded mace. The mixture is to be shaken 3 or 4 times
daily, coloured with caramel (burnt sugar), filtered at the end of ten
days, and set aside in bottles.
_Tears of the widow of Malabar_, are compounded with the preceding
quantity of spirits, sugar, and water, adding 4 drachms of ground
cinnamon, 48 grains of cloves, and a like quantity of mace, both in
powder. It may be slightly coloured with caramel.
_The delight of the Mandarins._--Take spirit, sugar, and water, as
above, adding 4 drachms of _anisum Chinæ_, (_Gingi_), as much _ambrette_
(seeds of the _hibiscus abelmoschus, Lin._) all in powder; 2 drachms of
safflower.
_The sighs of love._--Take spirits, water, and sugar, as above. Perfume
with essence (otto) of roses; give a very pale pink hue with tincture of
cochineal, filter and bottle up.
_Crème de macarons._--Add to the spirit, sugar, and water as above, half
a pound of bitter almonds, blanched and pounded; cloves, cinnamon, and
mace in powder, of each 48 grains. A violet tint is given by the
tinctures of turnsole and cochineal.
_Curaçoa._--Put into a large bottle nearly full of alcohol of
_trente-six_ (34° Baumé), the peels of six smooth Portugal oranges,
(Seville?) and let them infuse for 15 days; then put into a carboy 10
pounds of spirits of 18° B., 4 pounds of white sugar, and 4 pounds of
river water. When the sugar is dissolved, add a sufficient quantity of
the orange _zestes_ to give flavour, then spice the whole with 48 grains
of cinnamon, and as much mace, both in powder. Lastly introduce an ounce
of ground Brazil wood, and infuse during 10 days, agitating 3 or 4 times
daily. A pretty deep hue ought to be given with caramel.
_Swiss extract of wormwood_, is compounded as follows:--
Tops of the absinthium majus 4 pounds;
Ditto, absinthium minus 2 pounds;
Roots of angelica, }
Calamus aromaticus, } of each a few grains at pleasure;
Seeds of _anisum Chinæ_, }
Leaves of the dittany of Crete,}
Alcohol of 20° B., four gallons Imp.
Macerate these substances during eight days, then distil by a gentle
fire; draw off two gallons of spirits, and add to it 2 drachms of
essential oil of anise-seed. The two gallons left in the still serve for
preparing the _vulnerary spirituous water_.
Of colouring the _liqueurs_.
_Yellow_ is given with the yellow colouring matter of safflower
(_carthamus_,) which is readily extracted by water.
_Fawn_ is given by _caramel_, made by heating ground white sugar in an
iron spoon over a charcoal fire, till it assumes the desired tint, and
then pouring it into a little cold water.
_Red_ is given by cochineal alone, or with a little alum.
_Violet_ is given by good litmus (turnsole).
_Blue_ and _green_.--Sulphate of indigo gives the first. After
saturating it nearly with chalk, alcohol being digested upon it, becomes
blue. This tincture mixed with that of carthamus forms a good green.
LIQUID AMBER, is obtained from the _liquidambar styraciflua_, a tree
which grows in Mexico, Louisiana, and Virginia. Some specimens are thin,
like oil, and others are thickish, like turpentine. It is transparent,
amber coloured, has an agreeable and powerful smell, and an aromatic
taste, which feels pungent in the throat. Boiling alcohol dissolves it
almost entirely. It contains a good deal of benzoic acid, some of which
effloresces whenever the liquid amber hardens with keeping.
LITHARGE (Eng. and Fr.; _Glätte_, Germ.); is the fused yellow protoxide
of lead, which on cooling passes into a mass consisting of small
six-sided plates, of a reddish yellow colour, and semitransparent. It
generally contains more or less red lead, whence the variations of its
colour; and carbonic acid, especially when it has been exposed to the
air for some. time. See LEAD, and SILVER, for its mode of preparation.
LITHIA, is a simple earthy or alkaline substance, discovered not many
years ago, in the minerals called petalite and triphane. It is white,
very caustic, reddens litmus, and red cabbage, and saturates acids with
great facility. When exposed to the air it attracts humidity and
carbonic acid. It is more soluble in water than baryta; and has such a
strong affinity for it, as to be obtained only in the state of a
hydrate. It forms neutral salts with all the acids. It is most
remarkable for its power of acting upon, or corroding platinum.
LITHIUM, is the metallic basis of Lithia; the latter substance consists
of 100 of metal, and 123 of oxygen.
LITHOGRAPHY. Though this subject belongs rather to the arts of taste and
design than to productive manufactures, its chemical principles fall
within the province of this Dictionary.
The term _lithography_ is derived from λιθος, _a stone_, and γραφη,
_writing_, and designates the art of throwing off impressions upon
paper, of figures and writing previously traced upon stone. The
processes of this art are founded:--
1. Upon the adhesion to a smoothly-polished limestone, of an encaustic
fat which forms the lines or traces.
2. Upon the power acquired by the parts penetrated by this encaustic, of
attracting to themselves, and becoming covered with a printer’s ink,
having linseed oil for its basis.
3. Upon the interposition of a film of water, which prevents the
adhesion of the ink in all the parts of the surface of the stone not
impregnated with the encaustic.
4. Lastly, upon a pressure applied by the stone, such as to transfer to
paper the greater part of the ink which covers the greasy tracings of
the encaustic.
The lithographic stones of the best quality are still procured from the
quarry of Solenhofen, a village at no great distance from Munich, where
this mode of printing had its birth. They resemble in their aspect the
yellowish white lias of Bath, but their geological place is much higher
than the lias. Abundant quarries of these fine-grained limestones occur
in the county of Pappenheim, along the banks of the Danube, presenting
slabs of every required degree of thickness, parted by regular seams,
and ready for removal with very little violence. The good quality of a
lithographic stone is generally denoted by the following characters; its
hue is of a yellowish gray, and uniform throughout; it is free from
veins, fibres, and spots; a steel point makes an impression on it with
difficulty; and the splinters broken off from it by the hammer, display
a conchoidal fracture.
The Munich stones are retailed on the spot in slabs or layers of equal
thickness; they are quarried with the aid of a saw, so as to sacrifice
as little as possible of the irregular edges of the rectangular tables
or plates. One of the broad faces is then dressed, and coarsely
smoothed. The thickness of these stones is nearly proportional to their
other dimensions; and varies from an inch and two-thirds to 3 inches.
In each lithographic establishment, the stones receive their finishing,
dressing, and polishing; which are performed like the grinding and
polishing of mirror plate. The work is done by hand, by rubbing
circularly a movable slab over another cemented in a horizontal
position, with fine sifted sand and water interposed between the two.
The style of _work_ that the stone is intended to produce, determines
the kind of polish that it should get. For crayon drawing the stone
should be merely grained more or less _fine_ according to the fancy of
the draughtsman. The higher the finish of the surface, the softer are
the drawings; but the printing process becomes sooner _pasty_, and a
smaller number of impressions can be taken. _Works in ink_ require the
stone to be more softened down, and finally polished with pumice and a
little water. The stones thus prepared are packed for use with white
paper interposed between their faces.
_Lithographic crayons._--Fine lithographic prints cannot be obtained
unless the crayons possess every requisite quality. The ingredients
composing them ought to be of such a nature as to adhere strongly to the
stone, both after the drawing has undergone the preparation of the acid,
and during the press-work. They should be hard enough to admit of a fine
point, and trace delicate lines without risk of breaking. The following
composition has been successfully employed for crayons by MM. Bernard
and Delarue, at Paris:--
Pure wax, (first quality) 4
Dry white tallow soap 2
White tallow 2
Gum lac 2
Lamp black, enough to give a dark tint 1
Occasionally copal varnish 1
The wax is to be melted over a gentle fire, and the lac broken to bits
is then to be added by degrees, stirring all the while with a spatula;
the soap is next introduced in fine shavings; and when the mixture of
these substances is very intimately accomplished, the copal-varnish,
incorporated with the lamp black, is poured in. The heat and agitation
are continued till the paste has acquired a suitable consistence; which
may be recognised by taking out a little of it, letting it cool on a
plate, and trying its quality with a penknife. This composition, on
being cut, should afford brittle slices. The boiling may be quickened by
setting the rising vapours on fire, which increases the temperature, and
renders the exhalations less offensive. When ready, it is to be poured
into a brass mould, made of two semi-cylinders joined together by clasps
or rings, forming between them a cylindric tube of the crayon size. The
mould should be previously smeared with a greasy cloth.
M. Lasteyrie prescribes a more simple composition, said to be equally
fit for the lithographer’s use:--
Dried white tallow soap 6 parts.
White wax 6 --
Lamp black 1 --
The soap and tallow are to be put into a small goblet and covered up.
When the whole is thoroughly fused by heat, and no clots remain, the
black is gradually sprinkled in with careful stirring.