Thermometric Scales for Meteorological use 42 1 



is situated, the temperature falls every year below the 

 freezing-point of water. In some localities it passes quickly 

 through this point and remains constantly below, often 

 far below it, returning again in the spring and passing as 

 quickly through it again in the beginning of summer, to 

 remain constantly above it until it drops away again in the 

 fall of the year. In such places, where, however, the popu- 

 lation affected is limited, the use of Celsius' scale is not open 

 to very much objection. With the exception of a few days 

 in the fall, and again in the spring of the year,, the tem- 

 peratures are either continuously positive or continuously 

 negative ; and during one-half of the year the observer reads 

 his thermometer upwards, while during the other half of the 

 year he reads it downwards. When he has got well into 

 the one or the other half of the year, he will make no more 

 errors than those that he is personally liable to under circum- 

 stances of no difficulty. But at and near the two dates when 

 the temperature is falling or rising through that of melting 

 ice the case is very different. If the rise or fall is rapid, 

 his task is comparatively easy, and, after a few unavoidable 

 mistakes, he has succeeded in inverting his habit of reading. 

 But, in those parts of Europe and North America which 

 carry nearly the whole of the population, the temperature 

 in winter is frequently oscillating from one side to the other 

 of the melting-point of ice. If the observer is compelled to 

 use a thermometer which he must read upwards when the 

 temperature is on one side of that point, and downwards 

 when it is on the other side, and if he may be called on to 

 perform this fatiguing functional inversion several times in 

 one day, it is certain that he will suffer from exhaustion, and 

 that the observations will be affected with error. 



Were there no other thermometric scale available but that 

 of Celsius, we should simply have to put up with it, and 

 endure the inconvenience of it ; but, when we have another 

 scale, one devised primarily for meteorological observations 

 in the North of Europe, by a philosopher who constructed 

 it with a single eye to its fitness for what it was to be called 

 upon to measure, and when, in addition, this scale is still 



