James Croll — On the Glacial Epoch. 311 



But there is another circumstance which must be taken into ac- 

 count, viz. that the currents carrying moisture move in from all 

 directions towards the Pole, consequently the area on which they 

 deposit their snow becomes less and less as the Pole is reached, and 

 this must, to a corresponding extent, increase the quantity of snow 

 falling on a given area. Let us assume, for example, that the clouds 

 in passing from lat. 60° to lat. 80° deposit moisture sufficient to 

 produce, say, thirty feet of snow per annum, and that by the time 

 they reach lat. 80° they are in possession of only one-tenth part of 

 their original store of moisture. As the area between lat. 80° and 

 the Pole is but one-eighth of that between lat. 60° and 80°, this 

 would, notwithstanding, give twenty-four feet as the annual amount 

 of snowfall between lat. 80° and the Pole. 



Fifth. The enormous size and thickness of the icebergs which 

 have been met with in the Southern Ocean testify to the thickness 

 of the Antarctic ice-cap. 



We know from the size of some of the icebergs which have been 

 met with in the southern hemisphere that the ice at the edge of the 

 cap where the bergs break off must in some cases be considerably 

 over a mile in thickness, for icebergs of more than a mile in thick- 

 ness have been found in the southern hemisphere. The following 

 are the dimensions of a few of these enormous bergs taken from the 

 Twelfth Number of the Meteorological Papers published by the 

 Board of Trade, and from the excellent paper of Mr. Towson on the 

 Icebergs of the Southern Ocean, published also by the Board of 

 Trade.= With one or two exceptions, the heights of the bergs were 

 accurately determined by angular measurement : — 



Sept. lOfch, 1856.— -The " Lightning," when in lat. 55° 33' S., long. 140° "W., met 



with an iceberg 420 feet high. 

 Nov. 1839.— In lat. 41° S., long. 87° 30' E., numerous icebergs 400 feet high were 



met with. 

 Sept. 1840.— In lat. 37° S., long. 15° E., an iceberg 1000 feet long and 400 feet high 



was met with. 

 Feb. I860.— Captain Clark of the "Lightning," when in lat. 65° 20' S., long. 122° 



45' W., found an iceberg 500 feet high and three miles long. 

 Dec. 1st, 1859. — An iceberg 580 feet high and from two and a half to three miles 



long was seen by Captain Smithers of the "Edmond" in lat. 50° 52' S., long. 



43° 58' W. So strongly did this iceberg resemble land that Captain Smithers 



believed it to be an island, and reported it as such, but there is little or no 



doubt that it was in reality an iceberg. There were pieces of drift ice under 



its lee. 

 Nov. 1856.— Three large icebergs 500 feet high were found in lat. 41° 0' S., long. 



42° 0' E. 

 Jan. 1861. — Five icebergs, one 500 feet high, were met with in lat. 55° 46' S., long. 



156° 56' W. 

 Jan. 1861.— In lat. 56° 10' S., long. 160° 0' W., an iceberg 500 feet high and half a 



mile long was found. 

 Jan. 1867. — The barque "Scout" from the "West Coast of America, on her way to 



Liverpool, passed some icebergs 600 feet in height and of great length. 

 April, 1864. — The "Eoyal Standard" came in collision with an iceberg 600 feet in 



height. 



1 It is a pity that at present no record is kept, either by the Board of Trade or by 

 the Admiralty, of remarkable icebergs which may from time to time be met with. 

 Such a record might be of little importance to navigation, but it would certainly be 

 of great service to Science. 



