A NOTE ON 



THE METEOROLOGICAL WORK AND OBSERVATIONS ON 

 DEEP TEMPERATURES OF H. B. DE SAUSSURE 



BY H. R. MILL, D.Sc., LL.D. 



IN the second half of the eighteenth century the observational 

 sciences were only beginning to differentiate themselves from 

 the general study of Natural History and Natural Philosophy. 

 Meteorology was recognised as including observations of atmo- 

 spheric phenomena, but it was neither defined nor formulated. 

 Observations of the barometer, the thermometer, and the rain 

 gauge had been kept up intermittently for many years at a 

 few observatories and by a few travellers in distant parts of the 

 earth ; but with the exception of Halley's Theory of the Trade 

 Winds, these had led to no broad generalisations. Rapid progress 

 was taking place in the construction of instruments. The 

 barometer had been made sufficiently portable to be used for 

 determining the height of mountains ; the horrible diversity 

 of thermometer scales had been so far overcome that three amongst 

 the dozens which had been put forward had attained definite 

 prominence and that of Reaumur was fairly established on the 

 Continent. Hygroscopes, mostly based on the 'weather-house' 

 principle of changes in the length of a piece of cat -gut by absorbing 

 moisture, were common ; but these were useless for comparative 

 purposes owing to the want of any consistent method of graduating 

 the scale. As to the measurement of other meteorological 

 conditions each observer devised his own instruments, and the 

 methods of using the instruments varied according to the fancy 

 or the intelligence of the observer. 



While the barometer was in principle perfect from its invention 

 by Torricelli, its use was hampered in de Saussure's time by the 

 clumsiness of the subdivisions of units of measurement. His 

 observations were made in inches, lines (12 to an inch), sixteenths 

 of lines, and finally tenths of sixteenths, the task of adding up and 

 averaging a series of observations being thus a formidable piece of 

 compound addition and division. 



De Saussure was not so much concerned with the advancement 



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