422 Thermometric Scales for Meteorological use 



exclusively used in a large proportion of the meteorological 

 observatories of the world, it seems almost incredible that 

 amongst reasonable people, be they scientific or non-scien- 

 tific, there should be a powerful agitation to abolish the 

 scale which was devised for its work, which excludes error 

 in so far as it can be excluded, and to replace it by one 

 which, besides other defects, introduces, in the nature of 

 things and of men, avoidable errors, the elimination of which 

 is the first preliminary of the scientific treatment of all 

 observations in nature. 



Every meteorologist in northern countries who makes use 

 of the data which he collects knows that when his tempera- 

 tures are expressed in Fahrenheit's degrees, he can discuss 

 them at much less expense both of labour and of money for 

 computing than when they are expressed in Celsius' degrees ; 

 yet such is the apprehension of even scientific men when 

 brought face to face with the risk of being ruled "out of 

 fashion," that meteorologists who use Fahrenheit's scale, 

 though they fortunately do not give up its use, seem to be 

 disabled from defending it. 



What is this stupefying fashion, and can it not be made 

 out friend ? 



Fahrenheit lived and died before the decimal cult or the 

 worship of the number ten and its multiples came into vogue ; 

 but, whether in obedience to the prophetic instinct of great 

 minds or not, it almost seems as if he had foreseen and was 

 concerned to provide for the weaknesses of those that were 

 to come after him. The reformers of weights and measures 

 during the French Revolution rejected every practical con- 

 sideration, and chose the new fundamental unit, the metre, 

 of the length that it is, because they believed it to be an 

 exact decimal fraction one ten-millionth of the length of the 

 meridian from the pole to the equator. Is it an accident 

 that mercury, which was first used by Fahrenheit for filling 

 thermometers, expands by almost exactly one ten -thousandth 

 of its volume for one Fahrenheit's degree? 



Again, how did Fahrenheit devise and develop his thermo- 

 metric scale? A native of Danzig and living the first half of 



