PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 555 



the long leg of the siphon, and, as long as the steam continued 

 to be generated in quantity more than sufficient to fill the short 

 leg, the excess was forced around the bend of the siphon and 

 escaped through the column of mercury in the long leg. 



It was supposed by Mr. Frost and the committee of the Insti- 

 tute that all of the water in the tube was necessarily converted into 

 steam, as it was subjected to a temperature of 228^, while the 

 pressure was only three inches of mercury in addition to that of 

 the atmosphere. 



He now placed the tube in a bath of pure water, boiling, when 

 the three inches of steam was reduced to one inch, and with this 

 inch of steam, thus prepared, his experiments were conducted. 

 By placing the tube in a bath of salt water of such strength that 

 it would boil at a temperature of 216®, the one inch was 

 increased to two inches, and by inserting it in the saturated solu- 

 tion at 228°, it was expanded to three inches. 



From this experiment Mr. Frost drew the apparently manifest 

 conclusion that steam of 212*, heated apart from water, had its 

 volume doubled by the- addition of 4^" of heat, and trebled by 

 the addition of 16° of heat. From this law he pointed out the 

 enormous vahie of superheated steam. 



Mr. Frost's experiments having been recently repeated before 

 Mr. Isherwood, Mr. Rowell and others, the suspicion was excited 

 that there was water in the tube, together with the prepared 

 inch of steam, and Mr. Rowell devised a modification of the 

 experiment, to test this point. 



His first plan was to introduce just enough water to make an inch 

 of steam in the tube at the atmospheric pressure. By exceedingly 

 careful measuring and weighing he obtained the proper quantity 

 of water in a delicate glass bulb, which he pushed down througTi 

 the mercury into the short leg of the siphon. It was here eva- 

 porated at 212*, and then the tube was placed in the bath of 

 216*. But this steam was not doubled by the addition of the 4*^ 

 of heat. It was expanded only to the extent corresponding to 

 Guy Lussac's law. The same result followed its immersion in 

 the saturated solution of 228*. 



Subsequently a different plan was adopted for obtaining just 

 an inch of steam in the tube to experiment with. The tube was 

 placed in the saturated solution in nearly a horizontal position — 

 the open leg being slightly inclined upward — and the boiling was 

 continued until a very little more than an inch of steam remained. 



