CAOUTCHOUC 705 



and employing high pressure steam (described in Patent of 1843), he obtains what he 

 calls pure vulcanising, that is, the use of sulphur, rubber, and heat. He states ' That 

 by this mode, the greatest amount of extensile elasticity is obtained, and that this 

 quality is diminished in proportion as other matters are present in the compound.' 

 It may, however, be useful to record some of the results of early trials made by com- 

 petent authorities, with the view of testing its ultimate employments. Mr. Brocke- 

 don stated at the Institution of Civil Engineers, that he had kept vulcanised India- 

 rubber in tranquil water for 14 years without visible change, and he summed up the 

 then knowledge of trade production, that there was perhaps no manufacturing process 

 of which the rationale was so little understood as that of vulcanising caoutchouc ; all 

 was conducted on the observation of facts, a given quantity of sulphur to a certain 

 thickness of rubber, at a certain temperature ; and certain results were reckoned upon 

 with confidence, but more from practice than theory. Mr. Brockedon had placed 

 vulcanised rubber for 10 years in damp earth, and it exhibited no change. 



When articles were moulded, the metal of the mould was not a matter of indifference ; 

 if of tin, the article was usually delivered perfectly clean, but if of brass or copper, 

 then the material adhered to it, probably from the greater affinity of the sulphur for 

 the metal than for the caoutchouc : these surface effects may well be borne in mind, 

 for it appears not to be an easy matter to vulcanise large masses of caoutchouc, while 

 sheets and thin films are readily changed. The soft masses of materials are placed in 

 moulds, strongly secured, if a high temperature is to be used, and the mass comes out 

 with the form thus given to it, and more or less elastic ; hence the surface of a mass is 

 always likely to be advanced in the vulcanising changes. 



At present a very large proportion of the articles made have the forms given to 

 them in the plastic state, and then subjected to heat ; the change is effected, and they 

 retain their form, although rendered permanently elastic. 



Mr. Brockedon and Mr. Brunei tried this substance on the Great Western Railway, 

 in place of felt, to be used between the under sides of bearing rails and sleepers of 

 railways. It appeared, by constant trials of nearly a year, to be quite indestructible to 

 any action to which it had been exposed ; the slips were indented by the edge of the 

 rail, but not permanently so, and the surface was glazed, as if by friction ; the slips 

 were 6 inches wide, and weighed 8 oz. to the yard in length : the transit of the carriages 

 was easier over that part of the line. 



To test the power of endurance to heavy blows, Mr. Brockedon subjected a piece 

 of vulcanised India-rubber, 1 J inch thick and 2 inches in area, to one of Nasmyth's 

 steam-hammers of 5 tons ; this first rested on the rubber without effect, then was lifted 

 2 feet and dropped upon it without injury, then lifted 4 feet, and the vulcanised cake 

 was torn, but its elasticity was not destroyed. Still more severe trials were made : a 

 block of vulcanised caoutchouc was placed as between cannon balls, with the whole 

 power of the heaviest steam-hammers employed, but the iron spheres split the block, 

 and the elasticity of the vulcanised caoutchouc was not destroyed. 



Sheets of enormous size ship-sheets have been made 50 yards long and 56 inches 

 wide, others 1 feet square ; these are intended to pass over a steam-vessel's side, to 

 adapt a valve, fix a pipe, or repair, from the interior, the vessel itself, without going 

 into dock. These stout sheets, fths inch thick, are let down by ropes over a ship's 

 side, and brought over the hole or place for repair by the pressure of the water on 

 the elastic sheet, when the leak may be stopped and the ship pumped dry, pipes renewed, 

 shot-holes and leaks stopped. Indeed, an early application of compounds of native 

 rubbers and other materials was applied directly as sheathing for ships with success ; 

 but litigation among the parties caused the business to cease. Since the various plans 

 for getting a flexible material have been successful, there seems no doubt but many 

 unexpected applications will be made. 



Messrs. Macintosh had coated some logs of wood with vulcanised India-rubber, 

 and caused them to be towed in the wake of a vessel all the way to Demerara and 

 back, and it was found that the coated logs were quite intact, while the uncoated 

 timber was riddled by marine borers. The same firm stated: 'That the only effect 

 they could trace upon long immersed vulcanised caoutchouc, was a slight change of 

 colour, perhaps a hydrate produced by superficial absorption, but this change of 

 colour disappeared on being dried. If they were called upon to select a situation for 

 the substance to retain its properties for the longest period, they would select immer- 

 sion in water. After years of experience in the use of hose-pipes, pipe-joints, valves 

 for pumps and steam-engines, they had never known an injury from the contact of 

 any kind of water.' 



Mr. Goodyear sums up the advantages of vulcanised rubber under the following 

 heads, as being either properties new or superior to those possessed by the natural 

 caoutchouc : 

 VOL. I. Z Z 



