AMONGST THE SOUTHERN ICE. 245 



very little weight has been given to it, because, although ice 

 expands more under the influence of heat than any other known 

 solid, it is a bad conductor of heat, and the temperature of Swiss 

 glaciers is said not to vary. Now, whatever may be the case 

 with the tiny moribund glaciers of Switzerland, it seems to me 

 that in the case of the vast continental ice of the Antarctic 

 regions, and of the North in Greenland and elsewhere, a very im- 

 portant cause of motion must be expansion and contraction, due 

 to changes of temperature. In the Arctic regions there is a 

 considerable range of temperature below freezing point, and it is 

 impossible but that the ice, however bad a conductor it may be, 

 should not change its temperature very greatly, and constantly 

 when in an atmosphere which ranges during the day, for 

 example, between —10° F. and +19° F., a range of 29°. It is 

 admitted on all hands that a certain amount of motion of all 

 glaciers is due to expansion and contraction, produced by varia- 

 tion of temperature ; but it is contended that the proportion so 

 contributed to the general motion is insignificant in amount. 



The colouring of the southern bergs is magnificent. The 

 general mass has a sugar-loaf-like appearance, with a slight 

 blueish tint, excepting where fresh snow resting on the tops 

 and ledges, is absolutely white. On this ground-colour there are 

 parallel streaks of cobalt blue, of various intensities, and more or 

 less marked effect, according to the distance at which the berg 

 is viewed. Some bergs with the blue streaks very definitely 

 marked have, when seen from quite close, exactly the appearance 

 of the common marbled blue soap, (coloured plate, fig. 6). 



The colouring of the crevasses, caves, and hollows is of the 

 deepest and purest possible azure blue. None of our artists on 

 board were able to approach a representation of its intensity. 

 It seemed to me a much more powerful colour than that which is 

 to be seen in the ice of Swiss glaciers. In the case of the bergs 

 with all their sides exposed, no doubt a greater amount of light 

 is able to penetrate than in glaciers where the light can usually 

 only enter at the top. A large berg full of caves and crevasses, 

 seen on a bright dav, is a most beautiful and striking object. 



Glaciers by their weight only." Proc. Roy. Soc, 1869, p. 202. Also 

 " Phil. Mag.," May, 1869. Further papers in " Phil. Mag.," 1869, 1870. 



