THE "GREAT ICE AGE." 175 



so far as they went, afforded evidence in favor of is clayey 

 character. A further investigation of this would be very in- 

 teresting. 



But the most striking I may say astounding evidence of 

 the fertility of these banks, one which appeals most powerfully 

 to the senses, is the marvellous colony of sea-birds at Sverholt- 

 klubben, the headland between the two last-named fiords. I 

 dare not estimate the numbers that rose from the rocks and 

 darkened the sky when we blowed the steam-whistle in passing. 

 I doubt whether there is any other spot in the world where an 

 equal amount of animal life is permanently concentrated. All 

 these feed on fish, and an examination of the map will show 

 why in accordance with the above speculations they should 

 have chosen Sverholtklubben as the best fishing-ground on the 

 Arctic face of Europe. 



I am fully conscious of the main difficulty that stands in the 

 way of my explanation of the formation of the till viz. that 

 of finding sufficient water to float the ice, and should have 

 given it up had I accepted Mr. Geikie's estimate of the thick- 

 ness of the great ice-sheet of the great ice age. 



He says (page 186) that " The ice which covered the low 

 grounds of Scotland during the early cold stages of the glacial 

 epoch was certainly more than 2000 feet in thickness, and it 

 must have been even deeper than this between the mainland 

 and the Outer Hebrides. To cause such a mass to float, the 

 sea around Scotland would require to become deeper than now 

 by 1400 or 1500 feet at least." 



I am unable to understand by what means Mr. Geikic 

 measured this depth of the ice which covered these low 

 grounds, except by assuming that its surface was level with 

 that of the upper ice-marks of the hills beyond. The follow- 

 ing passage on page 03 seems to indicate that he really has 

 measured it thus : 



" Now the scratches may be traced from the islands and the 

 coast-line up to an elevation of at least 3500 feet ; so that ice 

 must have covered the country to that height at least. In the 

 Highlands the tide of ice streamed out from the central eleva- 

 tions down all the main straths and glens ; and by measuring 

 the height attained by the smoothed and rounded rocks we 

 are enabled to estimate roughly the probable thickness of the 

 old ice-sheet. But it can only be a rough estimate, for so 

 long a time has elapsed since the ice disappeared, the rain and 

 frost together have so split up and worn down the rocks of 



