72 



a coui'se of tliei'mometrical soundings was necessary to yield the I'equisite 

 data. He suggested that it was contrary to the ordinary course of nature 

 for the lower strata of the water to lie stagnant, and that either springs 

 at the bottom of the lake, or the difference of temperature between its 

 waters and those of the streams flowing into it from the snow-covered 

 mountains, might serve to keep up a circulation. 



Mr. McKerrow said no observations of temperature had been made 

 for depths of over 20 feet, but these had led to the conclusion that a 

 jjermanent temperature of 52° reigns at a moderate depth. The tempe- 

 rature of the Lake of Geneva at about 1-50 feet was constant at 41°. 



Mr. Beal explained how glaciers of the mass spoken of by Mr. 

 Thomson might have existed in ISTew Zealand during the glacial epoch. 



