AS APPLTED TO DENTISTBY. 143 



ratus similar to theirs, on as small a scale as it 

 could be made to operate, though it was at the 

 cost of over lOOL 



The size of my steam-chest was about that of 

 a 16-gallon cask, and the boiler of a capacity to 

 hold 150 gallons of water. 



This supply of water was not sufficient for one 

 heat of vulcanizing, as condensed steam in the 

 chamber had to be constantly drawn off and was 

 lost, while the boiler had to be refilled by a hand 

 force-pump, against a pressure of 70 to 80 lb. to 

 the square inch. 



I was enabled, however, by a series of ex- 

 periments — in the preparation of material and 

 otherwise — to reduce the time of vulcanizing from 

 twelve hours to six, and also to use less plaster 

 in investments. But the successful pieces were 

 even now only about three in five, resulting in 

 part from the improtected condition of the plaster 

 while steaming ; for occasionally it would separate 

 into a thousand fragments, caused by imperfect 

 moulding ; also, if an equal amount of plaster was 

 not used for each piece, the work was too hard, 

 or too soft, accordingly. 



At this period, in 1846, the necessity became 

 imperative for what are now called in America 

 ** Putnam's vulcanizing flasks." And, although 

 they appear simple to those now using them, I 

 have to acknowledge that a long series of experi- 

 ments and repeated alterations were necessary to 



