Date of the Glacial and the Upper Miocene Period. 375 



mud we kuow, from the accounts given by arctic voyagers, are 

 sometimes washed down upon the coast-ice; but certainly very 

 little of either can possibly get upon an iceberg. Arctic voyagers 

 sometimes speak of seeing clay and mud upon bergs ; but it is pro- 

 bable that it' they had been near enough they would have found 

 that what they took for clay and mud was merely dust and rubbish. 

 Undoubtedly the boulder-clay of many places bears unmis- 

 takeable evidence of having been formed under water ; but it does 

 not on that account follow that it was formed from the drop- 

 pings of icebergs. The fact that the boulder-clay in every case 

 is chiefly composed of materials derived from the country on which 

 the clay lies, proves that it was not formed from matter transported 

 by icebergs. The clay no doubt contains stones and boulders 

 belonging to other countries, which evidently have been trans- 

 ported by icebergs ; but the clay itself has not come from another 

 country. But if the clay itself has been derived from the coun- 

 try on which it lies, then it is absurd to suppose that it was 

 deposited from icebergs. The clay and materials which are 

 found on icebergs are derived from the land on which the ice- 

 berg is formed ; but to suppose that icebergs, after floating about 

 upon the ocean, should always return to the country which gave 

 them birth and deposit their loads is rather an extravagant sup- 

 position. And if they did not do that, then how could the 

 boulder-clay always be derived from the country in which it is 

 found ? 



Boulder-clay, whether formed on dry laud or under water, is evi- 

 dently the product of land-ice. Boulder-clay will be formed under 

 land-ice whether the ice be moving on dry land or alons; the sea- 

 bottom. In many parts of Englaud, as at Norwich for example, 

 the boulder-clay contains huge blocks which have evidently come 

 from Scandinavia and other distant parts on the back of icebergs. 

 These have been dropped among the clay then being brought 

 clown under the land-ice. In fact during the glacial epoch, 

 unless the seas around a country were completely blocked up by 

 land-ice, it would be impossible to prevent icebergs from coming 

 and discharging their loads occasionally amongst the clay forced 

 from under the land-ice. Few Scandinavian or other far trans- 

 ported blocks are found in the lower boulder-clay of Scotland ; 

 and this is owing, no doubt, to the fact that the seas surrounding 

 that country during the glacial epoch were so completely blocked 

 up by land-ice that no berg could possibly approach near to the 

 coast. 



If we simply admit (what follows from theory) that as the ice 

 began to accumulate on the land the sea beajan to rise, and that 

 the time of the greatest extension of the ice was also the time of 

 the greatest submergence, many a difficulty will disappear. 



