212 AMONGST THE SOUTHERN ICE. 



expansion, tlirough increase of temperature, of the denser ice 

 at the base of the mass. 



I may be allowed here to make a remark with regard to the 

 movements of glaciers, a subject to which my late father, the 

 Rev. Canon Moseley, devoted much time and research. The 

 theory propounded by him to account for the descent of 

 glaciers, which, as he proved most conclusively, cannot take 

 place by means of their weight alone, was that the motion was 

 due to the expansion and contraction of the mass. A heavy 

 body lying on a slope, inclined ever so little, and subject to 

 expansion and contraction, must necessarily crawl down the 

 slope, every change of dimensions tending to push the mass 

 in the direction of least resistance.* This theory has been 

 considered inadequate, and 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, ic 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 important cause of motion 

 must be expansion and contraction, due to changes of temper- 

 ature. 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 at- 

 mosphere which ranges during the day, for example, between 

 — io° F. and + ig° ¥., 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 variation of temper- 

 ature ; 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 loaf-sugar-like appearance, with a slight 

 bluish tint, excepting where fresh snow resting on the tops 

 and ledges is conspicuous as being 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. 



* Rev. H. Moseley, F.R.S., "On the Descent of Glaciers." Proc. Roy. 

 Soc, April 19th, 1855. " Gn the Mechanical Impossibility of the Descent 

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

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



