On Steam and Brines 



161 



Attention to these small matters is all-important, not only 

 in order to secure accuracy but also comfort in experimenting. 



Thermometers. Two thermometers were used for these 

 experiments, both made especially for me by Mr Hicks, of 

 Hatton Garden. One of them, A, was intended for use at 

 ordinary levels ; the scale was in Fahrenheit's degrees, and 

 ranged from 210 F. to 240 F. Each degree was divided 

 into tenths, and had a length of 7'2 mm. The length of a 

 Centigrade degree in this thermometer would thus have been 

 13 mm., and in order that the single divisions should not be 

 too far apart it would have had to be divided into twentieths 

 of a degree. 



The other thermometer, B, was especially made with a 

 view to experimenting on chloride of sodium at all available 

 heights above the sea. It was graduated into Centigrade 

 degrees and tenths, the length of one degree being 10 mm., 

 and the range was from 85 C. to 110 C. 



By the kindness of Dr Bilwiller, director of the Central 

 Meteorological Office of Switzerland, I was able to compare 

 the indications of this thermometer in saturated steam at 

 different heights with the temperatures which it ought to have 

 shown, on the basis of the atmospheric pressure as given by 

 the barometers of the central bureau at different stations. 

 For higher temperatures it was verified in terms of the 

 standard barometer of the Scottish Meteorological Society 

 in Edinburgh, which was obligingly put at my disposal by 

 Dr Buchan. The following are the readings in the order 

 of height : 



Thermometer B was compared at Kew, giving corrections 



