CONDITIONS OF CONTINENTAL ICE. 241 



the amount of ice being formed on the Antarctic con- 

 tinent were to become less than at present, both the 

 thickness of the sheet and the velocity of its motion 

 would become less. 



The following conclusions have now been estab- 

 lished : — 



1. The Antarctic ice-sheet must be thickest at the 



centre of dispersion and thinnest at the edge. 



2. The rate of motion of the ice must be least at the 



centre of dispersion and greatest at the edge. 



3. The mean thickness of the edge of the sheet, other 



things being equal, must be proportional to the 

 area of the sheet, and inversely as the rate at 

 which the edge is moving outwards. 



4. The area of the sheet, the thickness of its edge, 



the velocity of its motion outwards, the amount 

 of snowfall, and the temperature of the regions 

 are so related to one another that the value of 

 any one of them can be determined approxi- 

 mately in terms of the others. 

 The Probable Thickness of the Ice at the Pole. — The 

 point which now remains to be determined is, What is 

 the thickness of the ice at the Pole, or centre of dis- 

 persion ? The thickness of the sheet at the edge is 

 admitted to be about 1400 feet, and this, as has been 

 demonstrated, must be the thinnest part of the sheet. 

 It must gradually thicken inwards towards the Pole as 

 centre of dispersion, where the thickness reaches a 

 maximum. How much thicker, then, must the sheet 

 be at the centre than it is at the circumference ? The 

 question to be determined, stated in another form, is, 

 What is the thickness of ice at the Pole required in 

 order to impel the cap outwards in all directions at 

 the rate of a quarter of a mile per annum, or even 

 half that rate per annum ? The upper surface of the 



