PHYSICS 



that the entire work devolved upon Priestley till the end 

 of winter. Then Brocklehurst cut one in Blue Lake 

 which proved the deepest of all reaching water at 21 ft. 



A single series of observations at each shaft was of 

 but little value, especially as the admission of air to the 

 exposed surfaces caused very rapid changes. One shaft at 



Temperatures op Ice of Blue Lake 



Blue Lake, in which we had come on solid bottom at a 

 depth of 15 ft., was kept open for five months, from July 

 to December. Here periodic readings were taken, in 

 order to watch the rate at which the temperature at differ- 

 ent depths changed in correspondence with the air tem- 

 peratures. After some experience the shaft was covered 



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