278 Correspondence of J. Nickles. 
when drawn out and exposed toa heat of 115° C., would retain the 
length and size thus given it, and, moreover, it is also ready to be drawn 
anew. By drawing it thus, and re-heating it, successively, a thread of 
caoutchouc may be brought to any degree of fineness, limited only by 
the skill of the workman. A length of 50,000 metres may be obtained 
from a kilogramme of material. 
The thread thus obtained is of ordinary caoutchouc, but it is easy to 
make the vulcanized thread in the same manner. It is only necessary 
to incorporate into the pasty caoutchouc some flowers of sulphur, and 
heat up to 130 or 140°C. M. Gerard vulcanizes also by a process pe- 
culiar to himself, which consists in exposing the caoutchouc in an alka- 
line persulphuret to the action of a temperature of 150° h 
process gives good results, but the product is black. , 
or weaving, both kinds of thread, the vuicanized and non-vulcanized 
are used. Deprived of elasticity, the natural thread may be wor ed 
like any other textile material, and the elasticity may be afterwards re- 
stored, by passing a hot iron over the tissue. The vulcanized caout- 
chouc cannot be woven without the aid of a peculiar artifice ; it must 
be extended by weights. 
strength or homogeneity of the round even thread. 
Locomotion by compressed air.—I close this communication by some 
raulic press. 
By this method, M. Julienne. substitutes for the solid piston-— 
which a grain of sand may alter, which the slightest irregularity 10 the 
