1876 FROZEN LAKES. 59 



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. 



4 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. 



6 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 floebergs in 



