CONDITIONS OF CONTINENTAL ICE. 233 



becomes greater. — There is this peculiarity in conti- 

 nental ice, that there is a centre of dispersion from 

 which the ice radiates in all directions. This is 

 particularly true in reference to the Antarctic ice-cap. 

 It does not necessarily follow that the centre of 

 dispersion is the centre of the sheet. In the case of 

 the Antarctic sheet the centre of dispersion cannot, 

 however, be far from the Pole, and the Pole in all 

 probability is not far from the centre of the sheet. 

 We may therefore, in our inquiry, safely assume the 

 Pole to be the centre of dispersion. It is obvious that, 

 if the Antarctic ice be radiating in all directions from 

 the Pole as a centre, a portion of a layer which in, say, 

 latitude 85°, as was shown in Chapter V., covers 1 

 square foot of surface will, on reaching latitude 80°, 

 cover 2 square feet. At latitude 70° it will occupy 4 

 square feet, and at latitude 60° the space covered will 

 be 6 square feet. Then if the layer was 1 foot thick 

 at latitude 85°, it would be only 6 inches thick at 

 latitude 80°, 3 inches thick at latitude 70°, and 2 

 inches at latitude 60°. Had the square foot of ice 

 come from latitude 89°, it would occupy 30 square feet 

 by the time it reached latitude 60°, and its thickness 

 would be reduced to l-30th of a foot, or 2-5ths of an 

 inch. 



Now, the lower the layer the older it is, and the 

 greater the distance which it has travelled. A layer 

 near the bottom may have been travelling from the 

 Pole for the past 10,000 or 15,000 years, whereas a 

 layer near the top may perhaps not be twenty years 

 old, and may not have travelled the distance of a mile. 

 The ice at the bottom of a berg may have come from 

 near the Pole, whereas the ice at the top may not 

 have travelled 100 yards. It follows therefore that, 

 other things being equal, the lower a layer is the 



