CHAPTER XIV. 



PHYSICAL CONDITIONS OF THE ANTARCTIC ICE-SHEET. 



— Continued. 



Limit to Thickness of the Ice resulting from Melting produced by 

 Pressure. — Supposed Diminution in Thickness of Ice-strata from 

 Compression and Melting. — Centre of Dispersion. — Ice thickest 

 at Centre of Dispersion. — Thickness at Pole independent of 

 Amount of Snowfall. — Rate of Motion of the Antarctic Ice. — 

 Probable Thickness at the Pole. — Ice of the Glacial Epoch. 



Examination of the Reasons for Supposing that the 

 Antarctic Ice-cap is not of Enormous Thickness. 



1. Limit to the Thickness of the Ice resulting from 

 Melting produced by Pressure. — Pressure will produce 

 a melting of the ice in two totally different ways, viz., 

 either by lowering the melting-point or by the work 

 of compression. I shall consider both cases, and see if 

 any ground is afforded by either in support of the 

 conclusion that the Antarctic ice can be only one or 

 two thousand feet in thickness. 



(a.) Melting produced by the Lowering of the 

 Melting -"point. — The pressure exerted by a column 

 of ice of half a mile in height would, as we have 

 seen, lower the melting-point 1°; consequently, if the 

 column were at the temperature of 32°, its base, being 

 1° above the melting-point, would not remain in the 

 solid condition. To prevent the ice melting, the tem- 

 perature of the base would require to be as low as 31°. 

 Therefore, if 32° were the temperature of the Antarctic 



