36 Mammoth's Tooth. 



type. No. 1 is the lower boulder clay or till of the period of 

 intense glacial conditions. Nos. 2, 3, 4, and 5 have, I believe, 

 resulted from the denudation caused by vast floods flowing 

 from the end of the glacier that filled the valley of the Larne or 

 Inver River towards the close of the last glacial period. As the 

 climate became gradually more temperate, the glacier retreated 

 upwards towards the higher grounds, and the summer sun and the 

 great rains of that period brought down, first the sand which had 

 accumulated in the estuary of the ancient interglacial river, and 

 next, the coarse gravel and stones which form the No. 3 bed. 

 When the end of the glacier had melted on higher ground, the 

 fall of the torrent would tend to bring down coarser material 

 as in beds Nos. 3 and 5. How does this account for the inter- 

 vening layer (No. 4) of laminated clay ? I traced the formation 

 upwards, and I found the very beds of newer boulder clay (a 

 little above the town of Larne) from whose denudation this 

 layer must have been derived. The boulder clay at this place 

 had been protected from the erosive action of the large ice 

 sheet in the narrow gorge where its remains lie at the present 

 day. It was denuded when the glacier had retreated to higher 

 ground and had exposed it to the action of the summer floods. 

 I beg to call particular attention to this layer of laminated 

 clay, as it is in it 1 found the mammoth's tooth. The bed of 

 newer boulder clay, from which it has been derived, forms high 

 banks where the course of the present insignificant stream is 

 most rapid. In this upper boulder clay the mammoth's tooth 

 must have been protected from the grinding action of the last 

 ice sheet and subsequent glacier. Both were swept down 

 together as the glacier had retreated thus far up the valley. 

 After this boulder clay had been partially denuded, and dropped 

 as laminated clay on the lower grounds (with its mammalian 

 relics), the glacier still further retreated to higher grounds, and, 

 with milder climactic conditions, the floods, becoming more 

 intense, brought down another layer (18 inches) of very coarse 

 gravel with large rolled stones. To account for the larger 

 stones in the sand and gravel — some as much as io inches in 



