SOLIDS, LIQUIDS, AND OASES. 



James Watt concluded from his experiments that a given 

 weight of steam, whatever may be its density, or, in other 

 words, under whatever pressure it may exist, contains the 

 same quantity of heat. According to this, if we reduced 

 the pressure sufficiently to bring down the boiling-point to 

 112, instead of 212, the latent heat of the steam thus 

 formed would be 1066-6 instead of 966 -6, or if, on the 

 other hand, we placed it under sufficient pressure to raise 

 the boiling-point to 312, the latent heat of the steam 

 would be reduced to 866'6, i.e., only 866-6 more would 

 be required to convert the water into steam. If the boil- 

 ing-point were 412, as it is between 19 and 20 atmospheres 

 of pressure, only 766-6 more heat would be required, and 

 so on, till we reached a pressure which raised the boiling- 

 point to 1178-6; the water would then become steam 

 without further heating, i.e., the critical point would be 

 reached, and thus, if Watt is right, we can easily deter- 

 mine, theoretically, the critical temperature of water.* 



Mr. Perkins, who made some remarkable experiments 

 upon very high pressure steam many years ago, and exhibit- 

 ed a steam gun at the Adelaide Gallery, stated that red- 

 hot water does not boil; that if the generator be sufficiently 

 strong to stand a pressure of 60,000 Ibs. load on the safety, 

 valve, the water may be made to exert a pressure of 56,000 

 Ibs. on the square inch at a cherry-red heat without boil- 

 ing. He made a number of rather dangerous experiments 

 in thus raising water to a red-heat, and his assertion that 

 red-hot water does not boil is curious when viewed in con- 

 nection with Dr. Andrews' experiments. 



I cannot tell how he arrived at this conclusion, having 

 been unable to obtain the original record of his experi- 

 ments, and only quote the above second hand. It is 

 worthy of remark that the temperature he names is about 

 1170, or that which, if Watt is right, must be the criti- 

 cal temperature of the water. Perkins' red-hot water 

 would not boil, being then in the intermediate condition. 



So fur, we have a nice little theory, which not only shows 



* Watt's own figure for the latent heat of steam at 212 was 950, 

 but I adopt that which is now generally accepted. 



