1846.] MOTION COMPARED WITH TEMPERATURE OF THE AIR. 131 



observations in the summer of 1842 with the corresponding 

 changes of temperature.* That is to say, I have projected by 

 periods (corresponding to the intervals of observation on the 

 glaciers) the mean temperatures as observed at Geneva, and at 

 the Great St. Bernard, which are regularly published in the 

 Bibliotheque Universelle, the average of which (separately de- 

 duced from the mean of daily maxima and minima, and projected 

 in the upper part of the figure) may represent not inaptly 

 the average temperature to which the glaciers in question, and 

 especially the middle and lower regions of them, are exposed ; 

 and further, this average possesses the advantage of being de- 

 rived from data, wholly unconnected with the place or parties 

 where and by whom the observations on the motion of the 

 glaciers were made, and therefore are free from the remotest 

 suspicion of either in any degree influencing the other. 



Mean Temperatures (by periods) on the Centigrade Scale, 

 observed at Geneva and the Great St. Bernard, f 



A general comparison of the curves of temperature and those 



* Travels, p. 141. ^ f [Abridged from the original tables.] 



