ELASTIC BANDS. The manufacture of braces and garters, with threads of eaoutchouc, either naked or covered, seems to have originated, some time ago, in Vienna, whence it was a few years since imported into Paris, and thence into this country. At first the pear shaped bottle of Indian rubber was cut into long, narrow strips by the scissors ; a* single operative turning off only about 100 yards in a day, by cutting the pear in a spiral direction. He succeeded next in separating with a pair of pincers the several layers of which the bottle was composed. Another mode of obtaining fine threads was to cut them out of a bottle which had been rendered thin by inflation with a forcing pump. All these operations are facilitated by previously steeping the caoutchouc in boiling water, in its moderately inflated state. More recently, machines have been success fully employed for cutting out these fila ments; but for this purpose the bottle of caoutchouc is transformed into a disc of equal thickness in all its parts, and per fectly circular. This preliminary opera tion is executed as follows : 1st, the bot tle, softened in hot water, is squeezed between the two plates of a press, the neck having been removed beforehand, as useless in this point of view ; 2d, the bottle is then cut into two equal parts, and is allowed to consolidate by cooling before subjecting it to the cutting instru ment. When the bottle is strong enough, and of variable thickness in its different points, each half is submitted to power ful pressure in a very strong cylindrical mould of metal, into which a metallic plunger descends, which forces the eaout choue to take the form of a flat cylinder with a circular base. This mould is plunged into hot water during the coin- I pression. A stem or rod of iron, which goes across the hollow mould and piston, retains the latter in its place, notwith standing the resilience of the caoutchouc, when the mould is taken from the press.
The mould being then cooled in water, the caoutchouc is withdrawn.
The transformation of the disc of caoutchouc into fine threads is perform ed by two machines ; the first of which cuts it into a riband of equal thickness in its whole extent, running in a spiral direction from the circumference to the centre ; the second subdivides this riband lengthwise into several parallel filaments much narrower, but equally thick.
The threads, when brought to this state of slenderness, are put success ively into tubs filled with cold water ; they are next softened in hot water, and elongated as much as possible in the following man ner :—They are wound upon a reel turn ed quickly, while the operative stretches the caeutchouc thread with his hand. In this way it is rendered 8 or 10 times longer. The reels when thus filled are placed during some days in a cold apart. inent, where the threads become firm, and seem to change their nature.
This state of stiffness is essential for the success of the subsequent operations. The threads are commonly covered with a sheath of silk, cotton, or linen, by a braiding machine, and are then placed as warp in a loom, in order to form a nar row web for braces, garters, Rre. If the gum were to exercise its elasticity during this operation, the different threads would be lengthened and shortened in an irregular manner, so as to form a puckered tissue. It is requisite there fore to weave the threads in their rigid and inextensible, or at least incontractile condition, and after the fabric is woven to restore to the threads of caoutchoue their appropriate elasticity. This re storation is easily effected by passing a hot smoothing iron over the tissue laid smoothly upon a table covered with blanket stuff