Voyages of Discovery and Survey. 319 



transported ; for the beaches upon which the surf breaks in summer 

 would be frozen in winter, and worn masses might occasionally be 

 caught up in the ice, removing away from the shore, and be car- 

 ried within the power of some iceberg to pick them up, and, by cap- 

 sizino-, bring them to the surface and transport them. Occasionally 

 also we may anticipate that a part of the barrier itself, previously 

 attached to, and partly covering a beach, formed before the ice ad- 

 hered to that part of the land, may from local causes break away 

 and be carried northwards. In all cases the mineral matter borne 

 away by the icebergs would cover all inequalities in the bottom of 

 the ocean which it may fall upon, and thus the resulting accumula- 

 tion may be a mixture of large and small fragments, angular and 

 rounded (some perhaps scratched), mingled with mud and sand, the 

 whole arrano-ed in the most irregular manner, large masses of rock 

 strewed over and scattered througli clay. 



With respect to the turning-up of blocks of large size by the cap- 

 sizing of the icebero-s off these southei-n lands. Captain Wilkes, of the 

 United States Exploring Expedition, which descended into the Ant- 

 arctic regions in 1840, considers that he landed upon an upturned 

 icebercr, part of the icy barrier weathered by storms, about eight 

 miles distant from the main land, in latitude 65" 59' 40" S. On 

 this he found boulders, gravel, sand, and mud or clay, the larger spe- 

 cimens beinor described as of red sandstone and basalt. There was 

 also a kind of icy conglomerate, the matter cementing the stones 

 being formed of hard compact ice. One piece of rock imbedded in 

 it was estimated at about five or six feet in diameter. The same 

 navigator also mentions many icebergs discoloured by earth. Indeed 

 the evidence of the frequent overturn in these regions of icebergs 

 which had been aground, bearing the mud, gravel, and fragments of 

 rock on the bottom upwai*ds, appears complete, and is very important 

 as regards the distribution of detritus by means of icebergs. 



As not without its geological bearing, we may here glance at the 

 formation of the barrier itself. All the drawings made and informa- 

 tion received point to its accumulation in layers, in at least that part 

 of it projecting beyond the land into the ocean. The portion above 

 water is generally described as from 150 or 180, to 200 or 210 feet. 

 Captain Wilkes refers the formation of the ice in the first place to 

 ordinary field ice, upon which layers accumulate, varying from 6 inches 

 to 4 feet in thickness, from rain, snow, and even fog, so that the 

 mass descending by the increasing weight, part takes the ground, and 

 the other portions run out to sea over deeper water. 



The layers are proofs of successive accumulations, and as they vary 

 in their texture, they would point to modifications in the conditions 

 of the deposit at different times. We may assume that similar ac- 

 cumulations are effected on the land, disturbed only by volcanic out- 

 bursts and the showering of ashes and lapilli from volcanic vents for 

 the time in a sufficient state of activity, such showers extending as 



