TEMPERATURE 01' THE SEA, ETC. 635 



6. Specific Gravity of Sea Water (McClintock). 



(^Appendix to Record of Voyage of^' Fox^^ p. iii.) 



In this Appendix are contained the specific gravities of sea 

 water ; remarks on the state of the ice and on aurora and atmo- 

 spheric phenomena. 



The sp. gr. of surface water fell from 1 • 027 on the 9th of Aug. 

 1857 to 1*0208 on the 10th, when the yacht was surrounded by 

 icebergs. 



Temp. 



On Sept. 5th sp. gr. of sea at surface - 1 * 0265 28 • 8 



„ „ in 25 fathoms - 1*0290 29*0 



„ „ 50 „ - 1*0292 29*0 



„ „ 88 „ - 1*0302 29*0 



McClintock refers to freezing salt water and to evaporation 

 through ice (pp. 77, 78). 



On a calm day the temperature of the external air being —33°, 

 but within a snow hut the thermometer stood 17° higher, the 

 diiFerence being due to the transmission of heat through the ice 

 from the sea beneath. Evaporation goes on through ice from the 

 water underneath it. 



On the coast of Lapland, much salt is made from the sea or 

 floe ice, not from fresh water, glacier or pack-ice. 



In the drift down Baffin's Bay, McClintock remarks : — 



Sept. — Melville Bay. Ice drift affected by local cause. 



Dec. — In mid-channel a tendency to drift westward. 



Feb. and March. — Drifted parallel to the Greenland shore. 



April. — Ice deflected eastward by land to the west. Rapid 

 increase of drift. Could not ascertain the existence of current. 



A table of the winds and ice-drifts is given on p. 110. 



III.— PHYSICAL PROPERTIES OF ICE. 



1. First Grinnell Expedition under Commander De Haven 

 (1852). Forms of Ice. By Dr. Kane. 



De Haven, in his drift through Lancaster Sound and Baffin's 

 Bay, met with some very singular cases of the bending of large 

 blocks of ice. 



In one case, a table of ice, 4 feet thick, 18 feet long, and 15 broad, 

 was curved so as to form a well-arched bridge across a water 

 chasm. It had evidently reared high in the air, and then gra- 

 dually bent over. 



In another case, a straight block of rectangular section and 

 50 feet long resting on other blocks near its two ends, was bent 

 down by its own weight so as to form the arc of a circle. 



[The change of form produced in ice by pressure or by its own 

 weight is due to the fact that the temperature of the melting point 

 of ice is different under different pressures. Under pressure ice is 



