48 ACTION OF SEA-ICE. 



or more abundantly inhabited. Again, in shallow inlets, except for 

 Crustacea or other free-swhnniing animals, the bottom, continually 

 disturbed by the dropping of moraine or the ploughing up of bergs, 

 would be unfavourable for life. Accordingly, if the bed of the 

 Arctic Ocean in these places were raised, and we found the mouth 

 of a valley with laminated beds of clay rich in Arctic shells, and 

 the head bare of life, but still showing that the beds had been 

 assorted by marine action, supposing we were (as in Scotland) 

 ignorant, except by analogy, of the history of this, should we not 

 feel justified in saying that the beds at the one place and the other 

 were deposited under different conditions, and were in all likeli- 

 hood of different ages ? How just that apparently logical inference 

 would be I need scarcely ask. 



5. Action of Sea-Ice. 



We have in the previous section in the most outline form sketched 

 the subject of Greenland glacial action. As the object of this paper 

 is not to form a summary of our knowledge on the subject, I have 

 not entered into a discussion of any points on the physics of ice, 

 further than was necessary to a right understanding of the subject 

 in hand. Suffice it to say that all sea-ice forms originally from the 

 " bay-ice " of the whaler, as the thin covering which first forms on 

 the surfaces of the quieter waters is called, and that this " bay-ice " 

 is almost entirely fresh, the effect of Arctic freezing temperature 

 being to precipitate the salt. Hence, when we talk of the tempera- 

 ture requisite to freeze salt water, it is merely equivalent to saying 

 that this temperature is requisite for the precipitation of the saline 

 constituents of the water. The water of the Arctic Sea is, accord- 

 ing to Scoresby, of the specific gravity 1-0263. 1 At this specific 

 gravity it contains of oz. (avoird.) of salt to every gallon of 231 

 cubic inches, and freezes at 28^° Fahr. The specific gravity of this 

 ice is about 0*873. To enter upon this subject, of which the above 

 is only the summary of a long series of experiments, is foreign to 

 the object of this paper. From this bay-ice is formed the floe, 

 from the floe the pack-ice, and other forms familar to Arctic navi- 

 gators. In the summer the ice in Davis Strait on either side breaks 

 up sooner than that in the middle of the Strait, which remains for 



1 In au interesting series of experiments by Dr. Walker of the Fox Expedition, 

 it was shown that the bay-ice was never entirely free from salt. If sea water is 

 frozen its specific gravity is 1005, showing salts, especially chloride of sodium or 

 common salts. Fresh water is often frozen on the surface of the salt. — (' Journ. 

 Eoy. Dublin Soc, I860,' vol. ii. pp. 371-380.) 



