164 GOODYEAR ON GUM-ELASTIC. 



mould for each separate article for the latter, besides the labor 

 of handling them in the manufacture, would be too great to be 

 practicable. The invention of vulcanizing the veneers between 

 plates of metal under pressure, and that of vulcanizing the small 

 and embossed articles made of hard compounds in finely pul- 

 verized soapstone and other fine earths, were made by the 

 writer almost simultaneously with the want felt for the pro- 

 cesses, in consequence of the invention of the things alluded 

 to. These methods may be said to be indispensable to the 

 manufacture of the foregoing articles with success. And a 

 few of the first specimens of them were only produced in time 

 for the London Exhibition of 1851, to which they were for- 

 warded. 



SOLARIZATION. 



When caoutchouc prepared with sulphur is exposed to the 

 action of the sun's rays for several hours, a change is produced 

 in the surface of the caoutchouc, which may be called natural 

 vulcanization. The solarizing of India rubber fabrics com- 

 pounded with sulphur was practiced by the writer previous to 

 the discovery of the artificial vulcanizing process. Upon the 

 discovery of the process of vulcanizing by means of artificial 

 heat, the solarizing process was abandoned ; but recent improve- 

 ments made by the author in the manufacture of caoutchouc 

 fabrics, lead us to anticipate that solarization will again be 

 used very extensively, particularly for the gutta percha variety 

 of caoutchouc. 



The effects of solarization extend to only a slight depth, and 

 the process is not therefore applicable or useful with thick 

 sheets or masses of caoutchouc ; but in all the thin fabrics, or 

 the fabrics upon which a thin sheet of caoutchouc is spread, 

 solarization is an effectual and cheap process of curing India 

 rubber.* 



* The reader Is here referred to page 73. 



