though far surpassing the latter in most of its qua- 
lities; it can be made into a paper ; it can be made 
of any required thickness or thinness; it will re- 
ceive white and coloured grounds, on which more 
| delicate lines of engraving are impressed than on 
_any kind of paper; articles are made up from 
these materials with great ease and rapidity by 
simply cutting out and cementing pieces toge- 
| ther more firmly than can be effected by the 
needle. We distinguish two kinds of caoutchouc, 
—the common material, and that composed ac- 
cording to Goodyeayr’s process. 
The crude material, as imported in skinny 
| shreds, fibrous balls, twisted concretions, cheese- 
like cakes, and irregular masses, is more or less 
impure, and sometimes fraudulently interstrati- 
fied with earthy matter. It is cleansed by being 
cut into small pieces, and washed in warm water. 
It is now dried on iron trays, heated with steam, 
while being carefully stirred about to separate 
| any remaining dirt, and is then passed through, 
_ between a pair of iron rollers, under a stream of 
| pieces being blended together. 
| water, whereby it gets a second washing, and be- 
comes at the same time equalized by the separate 
The shreds and 
cuttings thus laminated, if still foul or hetero- 
geneous, are thrown back into a kind of hopper 
over the rollers, set one-sixteenth of an inch apart, 
and passed several times through between them. 
The large and thick tables of the gum are sliced 
| into cakes for the stationer, and into sheets for 
making tapes and threads of caoutchouc. The 
thin slices constitute what is called sheet-caout- 
chouc, and they serve tolerably for making tubes 
for pneumatic apparatus, and sheaths of every 
kind; since, if their two edges be cut obliquely 
with clean scissors, they may be made to coalesce, 
by gentle pressure, so intimately, that the line of 
junction cannot be discovered either by the eye 
or by inflation of a bag or tube thus formed. 
Sheets of caoutchouc are cut into continuous 
threads by highly ingenious machines. The 
threads of caoutchouc are readily pieced by par- 
ing the broken ends obliquely with scissors, and 
then pressing them together with clean fingers, 
taking care to admit no grease or moisture within 
the junction line. These threads must be de- 
prived of their elasticity before they can be made 
subservient to any torsile or textile manufacture. 
Hach thread is ¢nelasticated individually in the 
act of reeling by the tenter boy or girl pressing 
it between his moist thumb and finger, so as to 
stretch it to at least eight times its natural 
length, while it is drawn rapidly through be- 
tween them by the rotation of a power-driven 
reel. This extension is accompanied with con- 
densation of the caoutchouc, and with very con- 
siderable disengagement of heat. The reels, after 
being completely filled with the thread, are laid 
aside for some days, more or fewer, according to 
the quality of the caoutchouc,—the recomposed 
requiring a longer period than the bottle-mate- 
rial. When thus rendered inelastic, it is wound 
CAOUTCHOUC. 
679 
off upon bobbins of various sizes, adapted to va- 
rious sizes of braiding, or other machines, where 
it is to be clothed with cotton or other yarn. 
For waterproof fabrics, the parings, the waste 
of the kneading operations above described, and 
the coarsest qualities of imported caoutchouc, 
such as the inelastic lumps from Para, are 
worked up into varnish, wherewith two surfaces 
of cloth are cemented, so as to form a compound 
fabric, impervious to air and water. The caout- 
chouc is dissolved either in petroleum (coal-tar), 
naphtha, or oil of turpentine, by being triturated 
with either of the solvents in a close cast-iron 
vessel, with a stirring apparatus, moved by me- 
chanical power. The heat generated during the 
attrition of the caoutchouc is sufficient to favour 
the solution, without the application of fuel in 
any way. Three days are required to complete 
the solution of one charge of the varnish mate- 
rials. The proportion of the solvent oils varies 
with the object in view, being always much less 
in weight than the caoutchouc. 
Metallic Gum Elastic Composition—The follow- 
ing specification and claim of Goodyear’s Patent 
is from the Journal of the Franklin Institute. 
“ My principal improvement consists in the com- 
bining of sulphur and white lead with India rub- 
ber, and in the submitting of the compound, thus 
formed, to the action of heat, at a regulated tem- 
perature ; by which combination and exposure to 
heat it will be so far altered in its qualities as 
not to become softened by exposure to the solar 
rays, or of artificial heat, at a temperature below 
that to which it was submitted in its preparation, 
say to a heat of 270° of Fahrenheit’s scale; nor | 
will it be injuriously affected by exposure to 
cold ; it will also resist the action of the expressed 
oils, and that, likewise, of spirits of turpentine, 
and of the other essential oils, at common tem- 
peratures, which oils are its usual solvents.” The 
compound may be formed of various proportions 
of the ingredients, but that which is deemed 
best consists of twenty-five parts of India rubber, 
five of sulphur, and seven of white lead—the 
India rubber having been previously dissolved in 
some of the essential oils, and the sulphur and 
white lead ground in the manner of preparing 
paint. 
“T have repeatedly experimented on this com- 
position,” says Mr. Booth, “which is a singular 
compound of sulphuret of lead with caoutchouc, 
and found it materially altered in some of its 
properties. It is more perfectly elastic than 
common caoutchoue, for after a long continued 
compression or extension, it returns precisely to 
its former dimensions ; it seems to possess greater 
tenacity, requiring a considerable force to pro- 
duce rupture; it is equally flexible, or nearly so, 
in summer and winter temperatures, differing in 
this respect remarkably from common caout- 
chouc; it resists the action of the usual solvents 
of caoutchouc in an extraordinary degree, being 
insoluble in ether and the essential oils, and 
