1876 FROZEN LAKES. 50 



the water only attains a thickness of about seven feet. 

 Last winter the mean temperature of the atmosphere 

 for two months was as low as minus 39°, more than 

 seventy degrees colder than the quiescent water left 

 unfrozen below the ice. 



' To what extent the seven feet of ice and its cover- 

 ing, two feet in depth, of such a slow conductor as 

 snow, prevents the escape of warmth from the water 

 below, which must take place before the ice can form, 

 is an interesting question. During the winter a ther- 

 mometer buried eighteen inches in the frozen ground 

 registered a minimum temperature of minus 12°. For 

 fifty-three consecutive days the mean temperature of 

 the air was minus 44° ; which gives the large difference 

 of 32° as being due to eighteen inches of frozen soil 

 and ice.' 



Doctor Moss, a very careful observer, after a close 

 study of the Polar floes, differs from me regarding their 

 formation. As the subject is highly interesting I 

 append the following remarks which express his con- 

 clusions : — 



' The neve-like stratification, the imbedded atmo- 

 spheric dust, and the chemical characters of our Polar 

 floes indicate, in my opinion, that they are the accu- 

 mulated snow-fall of ages rendered brackish by infil- 

 tration and efflorescence. 



' Until Sir George Nares showed me the part of his 

 MS. treating of the growth of the Polar floes, I had no 

 idea that the universality of their stratification would 

 be at all called in question. My notes were, therefore, 

 not made to prove this point, and yet I find amongst 

 them nine sketches made from nature of fioebergs in 



