96 Dr. Masons Description 



converts the 3 atoms of sulphurous into sulphuric acid, 

 while the acid thus decomposed makes its escape iu the 

 form of deutoxide of azote. 



The preceding analysis was repeated with very nearly 

 the same result. If the supposition of the saline matter 

 containing |^ths of sulphuric and |-ths of sulphurous acid 

 be admitted, then the constitution of the portion examined 

 must have been 



Sulphurous acid . . . 63-87 



29-875 

 Probably the water was in combination with the sulphuric 

 acid. 



Article III. 

 Description of a New Hygrometer ; illustrated by experiments 

 and a comparison of its results with Sir John Leslie's, and 

 the Dew-point Hygrometers, by John Abraham Mason, 

 M.D., Member of the Royal College of Surgeons, Edin- 

 burgh; Extraordinary Member of the Royal Medical 

 Society, Edinburgh, Sfc, 



I WILL resume the subject of my former paper by entering 

 into a consideration of the general Law which regulates 

 the action of my Hygrometer. 



1. The ^waZ tension of the vapour given off in the pro- 

 cess of evaporation is determined, not by the temperature 

 of the evaporating surface ; but by the elasticity of the 

 aqueous atmosphere already existing: the quantity of 

 vapour given off depending upon temperature, while the 

 refrigeration produced by that process depends entirely 



