200 



ON SUPERHEATED STEAM. 



tion of steam to the hardening of rubber, I will 

 proceed to explain its merits, safety, and sim- 

 plicity. The vnlcanizer, Fig. 26, is made very thick. 



Fig. 26. 



not fi'om the necessity of so much strength, but 

 because the gas burnt underneath and the sulphur 

 inside both tend to wear it away ; and cast iron 

 has been preferred because it is much less acted 

 upon by gases, water, or acids, than other metals, 

 as copper, malleable or wi'ought iron. 



The vessel may be filled with an atmosphere of 

 steam, either by putting in as much water as will 

 be vapourized, or by the emission of steam from 

 the plaster or any hydrated solids. I prefer very 



* Section of Childs' Vulcanizer. 



