CAOUTCHOUC 707 



applied to the various emergencies of gas engineering. India-rubber gas-tubing is 

 now in general use, the great advantage over metal tubes being, the ease -with which 

 gas can be conveyed to whatever part of the building it may be required in ; this, where 

 any alterations are being effected, is a great desideratum. Ballast bags, large stout 

 bags of India-rubber and canvas, capable of holding from 1 to 5 or 10 tons of water, 

 are coming into use as the most convenient form of ballast, thus saving valuable space 

 which is made available for cargo. These bags may be emptied at any time, and when 

 flattened down and rolled up, can be conveniently stowed away. India-rubber bags for 

 inflation have also in a few cases been made use of for buoying up vessels, but hitherto 

 the practice has been experimental only, and such floating machines are not as yet 

 generally in use. 



The vulcanising of India-rubber on silk or woollen goods was for a long time considered 

 impracticable, because the process of vulcanisation destroyed the fibre and texture of 

 the two substances ; but it is stated that now this process is effected in a manner 

 which deprives neither silk nor wool of their natural qualities and strength. By this 

 improvement, combined with Silver's patent process of annihilating the unpleasant 

 smell which all India-rubber goods used to acquire in the process of manufacture, the 

 advantages of that substance for clothing purposes are extended to the lightest and the 

 warmest of our textures. Silk and India-rubber garments are made without any de- 

 terioration of the strength and durability of the stuff, while they are perfectly free from 

 odour of any kind. 



V. MECHANICAL APPLICATIONS OF CAOUTCHOUC. 



Numerous important applications of caoutchouc have been made in the mechanical 

 arts, among which we may mention, springs for railways and common road carriages, 

 military carriages, lifting springs for mining ropes and chains, towing ropes and 

 cables, rigging of ships, recoil of guns on ships, the tyres and naves of railway and 

 other wheels, axles and axle bearings, windows of railway carriages, railway 

 switches, bed of steam-hammer, couplings for locomotives and tenders, packing for 

 steam and water joints, shields for axle boxes, sockets for water pipes, bands for 

 driving machinery, valves for pumps, tubes for conveying acids, beer, water, and other 

 fluids, packing for pistons, &c. 



The Exhibition of 1862 presented to us an enormous display of India-rubber 

 manufacture. The applications of caoutchouc to driving belts for machinery, to 

 washers and buffers, were numerous, and many of them excellent. 



Messrs. Perreaux and Co. were exhibitors of a valve for pumps made of vulcanised 

 caoutchouc. Its simplicity and efliciency were remarkable : the valve was simply a 

 cylinder of India-rubber, with its two sides at the uttermost end pressed together like 

 lips, and then vulcanised, which makes the material retain the form given to it. This 

 valve, when in position, was open below, and closed above in the form of a wedge ; the 

 fluid easily passes upwards owing to the elasticity of the material, but the downward 

 pressure firmly closes the lips and prevents return. Of ebonite and kamptulicon ' 

 there were many examples, embracing a curious variety of articles from philosophical 

 apparatus in the form of electrical machines, to pieces of furniture, and ornaments 

 for ladies' wear. See EBONITE and KAMPTULICON. 



Springs. The first proposal to use caoutchouc for springs that we are aware 

 of occurs in Lacetfs patent, in 1825, when blocks of caoutchouc were proposed 

 to be used, having dividing plates of iron between each series ; but little seems to 

 have been done towards any practical application at that time : later, in 1844, Melville 

 proposed to use spheres of caoutchouc, enclosing air, and separated by discs of 

 wood or metal, the whole being enclosed in iron cases, and used for buffers and 

 bearing springs for railway carriages. In 1845 Walker and Mills proposed to use 

 bags of caoutchouc enclosing air, and contained in cases of iron, for use as buffer 

 springs. 



The next improvement is contained in Fuller's patent of 1845, which consists in the 

 use of cylindrical rings of vulcanised India-rubber, in thicknesses varying from to 

 3 inches, and with diameter of ring suitable to the power of spring required ; between 

 each of these cylindrical rings he places a thin iron plate, through a hole in the 

 centre of which passes a guide rod. Fig. 409 shows Fuller's spring in section and plan. 

 These springs have been extensively used as buffer-, bearing-, and draw-springs for railway 

 uses, alone and in combination with De Bergue's improvements : some defects have been 

 found in practice in this form, to obviate which, the ingenuity of later inventors has 

 been exercised ; the defects alluded to are, the tendency to swell out at the central 

 unsupported part of the ring, thus from the undue tension rendering it liable to break 



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