486 Mr. J. Gill on the Temperature of the 



its passage), it would take the temperature of 109°, and retain 

 it after being again drawn up to its original position in the 

 midst of the steam where just before it had shown a temperature 

 of 100°. What mysterious virtue can be imagined to exist in the 

 film of brine coating the thermometer which should, through a 

 range of 9° in this case, render it insensible to thermic influence 

 supposed to be universal ? Does the phenomenon depend merely 

 on the circumstance of the thermometer being coated with a film 

 of some liquid in general ? Certainly not ; for if the thermo- 

 meter be heated in an oil-bath instead of an air-bath as described, 

 and inserted in the neck /' with the adhering film of oil, it shows 

 very nearly the same as when dry ; and no doubt similar results 

 would be obtained with any liquid coating not evaporable in the 

 steam, and between which and the steam no chemical action 

 takes place. It was known long ago that the action of the va- 

 pour of water at 100° on saline solutions, or on crystals of a salt, 

 may produce temperatures higher than 100°; but it has not 

 been supposed that any substance resulting from the combina- 

 tion of a salt with water should, after the chemical action had 

 ceased, continue to retain its higher temperature during an in- 

 definite time in an atmosphere of steam at 100°. M. Eiidorff, a 

 pupil of Magnus, who revived the method of experimenting with 

 a hot thermometer on the vapours of solutions, used by Faraday 

 more than forty years ago, conceived also the idea of first plun- 

 ging the thermometer into the boiling solution, and after a while 

 raising it into the superincumbent steam ; but it appears, from 

 the paper of Magnus above referred to, that he could deduce no 

 certain results from this method. Had he maintained his boil- 

 ing solutions at a constant degree of saturation, and kept the 

 interior surfaces of his apparatus constantly wet with a film of 

 the hot liquid, he might have been astonished to observe the 

 paradoxical phenomenon of a body considerably hotter than 100° 

 remaining in a steam-bath at 100° during an indefinite time 

 without lowering its temperature. 



If the brine communicated heat to the steam (as we might 

 suppose from the experiments of Magnus), the steam must be- 

 come superheated in proportion as the brine is cooled ; and if 

 the masses of brine and of steam in contact (supposing them 

 isolated from all exterior causes of heating or cooling) were 

 exactly proportioned to their respective thermic influences, it 

 might perhaps be imagined, on a superficial view of the case, 

 that an equalization of temperature might take place between 

 them, the brine becoming colder and consequently tending to 

 condense steam, and the steam becoming superheated and con- 

 sequently resisting the absorbent action of the brine. But when 

 the film of brine is in permanent contact with an unceasing cur- 



