THE RENEWAL OF ANTARCTIC EXPLORATION. 363 



No sooDer do these great ice islands — these majestic and sublime sen- 

 tinel outposts — of Antarctica sail forth on their new career, than they 

 collide the one with the other; the fragments of imiiact are scattered 

 over the surface of the ocean, and, with similar fragments derived from 

 the steeper land slopes, with salt-water ice, and accumulations of snow, 

 they form what is known as the paclx. This pack, when heavy and 

 closely set, has been erroneously called by Wilkes and other writers 

 the ice barrier — a name which should only be used to designate the 

 solid continuous ice wall that is pushed into the sea from the central 

 regions of the continent, such as that along which Ross sailed for 300 

 miles. 



Waves dash against the vertical faces of the floating ice-islands as 

 against a rocky shore, so that at the sea level they are first cut into 

 ledges and gullies, and then into caves and caverns of the most heavenly 

 blue,* from out of which comes the resounding roar of the ocean, and 

 into which the snow-white and other petrels may be seen to wing their 

 way through guards of soldier-like penguins stationed at the entrances. 

 As these ice islands are slowly drifted by wind and current to the north, 

 they tilt, turn, and sometimes capsize, and then submerged prongs and 

 s]nts are thrown high into the air, producing irregular pinnacled bergs 

 higher, possibly, than the original table-shaped mass. As decay pro- 

 ceeds, the imprisoned bowlders, stones, and earth are deposited over 

 the ocean's floor as far as sub-tropical regions. 



Tlie late ]Mr. Croll used to speak of an accumulation of ice and snow 

 at the South Pole 10 and even 20 miles in thickness; but from all we 

 know of the properties of ice, and the relation of its melting or freez- 

 ing point to temperature and pressure, it is highly improbable that such 

 a thickness of ice will be found on any part of the Antarctic continent. 

 If the snow cap rests on rock of a temperature half a degree below the 

 freezing point, then the greatest thickness of ice formed on the conti- 

 nent would not likely exceed 1,000 or 1,800 feet, and this appears to be 

 just a little more than the greatest thickness of the great ice barrier 

 when it is floated oft' into tlie ocean as ice islands. This may possibly 

 represent the greatest thickness that can be formed under existing con- 



most probable that the height above water is about oue-seveuth of the total thick- 

 ness of the berg. — See Murray, " The Exploration of the Antarctic Regions," Scot. 

 Geofjr. Mag., 1886, vol. ii, p. 553. 



* The deep bine color is tine to the fact that all the air has been expelled from the 

 deeper parts of the ice cap bj^ the coustaut melting andregelation which tal<es place 

 thronghont the whole mass as it moves over the land. When a cannon ball was 

 fired into this azure-blue ice the ball did not penetrate, but large masses of ice fell 

 away, the fractures having a conchoidal appearance like glass. When a ball was 

 fired into the upper areolar Avhite layers of a table berg it penetrated without pro- 

 ducing any visible effect. Fragments of the white areolar layers were subjected to 

 pressure and impact on board ship, and it was observed that these fragments could 

 be easily deformed, while fragments of th(( transparent a/.ure-blue ice behaved (juite 

 dilferently iinder the same tests, resembling a purely crystalline substance. 



