146 ON THE VULCANITE BASE 



cylinder, the quantity regulated by a suction- 

 valve, acted upon by pressure from without, and 

 by heat within. 



After more than one hundred consecutive ex- 

 periments with this. apparatus, and having varied 

 it and the application of heat (with and without 

 the steam made through the red-hot coil), in 

 every possible form which I could imagine, and 

 without obtaining satisfactory results, I turned 

 my attention to the use of an oil-bath. 



This I had constructed, using two cans, one 

 smaller than the other. 



The largest, being one-third full of common oil, 

 was placed upon an ordinary stove to heat, and 

 the smaller cylinder or can was then let down 

 into the oil, resting on a flange near the top of it, 

 which made the large can tight. 



The work was then put into the small cylinder, 

 which closed by an adjustable cover, into which 

 the thermometer was attached. 



The boiling point of oil being about 500 de- 

 grees, a vulcanizing heat was readily obtained, 

 and before the least ebullition of the oil took 

 place. But the results of this apparatus proved 

 the same as those made with the last one de- 

 scribed; viz., that under certain conditions of the 

 plaster some pieces were made hard, but in all 

 cases having such imperfections as to deter me, 

 for the time, from making further experiments on 

 this point. 



