INFILTRATION OF SALT. Z91 
tic migration really began. The air was checkered 
now with moving columns of hirds : the families Uria 
and Somateria, the auks and the eiders, flew over us 
in continuous crowds. 
It was at this time that the floe, which had so long 
been our homestead, began to show symptoms of de- 
cay. The mean thickness of^our pack — the mean of 
many measurements — might be regarded as eight feet ; 
although the ice-tables were in some cases so thrust 
one under the other, as to increase it to twenty and 
even thirty feet. Our great pack probably extended 
in a contiguous line from Lancaster Sound to Cape 
Walsingham, with a breadth of not less than two hund- 
red miles. 
It was interesting to observe the compensations by 
which Nature got rid of this vast accumulation. The 
simple effects of solar heat, whether from the atmos- 
phere above or the heated currents below, do not sat- 
isfactorily explain the dissolution of this ice. Changes 
in its mechanical structure evidently took place, pre- 
paring the way for the subsequent actions of thaw. 
My attention was first called to this fact by hearing, 
through my friend. Lieutenant Brown, that the observ- 
atory of Sir James Ross at Leopold Island was moist 
and saggy, while the outside ice remained dry and 
firm. In the month of May, while our mean temper- 
ature was still below the freezing point, I noticed, dur- 
ing my walks over the ice, that certain surface-floes, 
which had been during the winter hard and fresh, 
began to yield under me as I walked, and gave a 
decidedly brackish taste to the palate. The ice, too, 
in many cases lost its tenacity and resistance. Our 
coal, which had been thrown out loosely on it, so de- 
pressed the little area around it, as to be surrounded 
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