OF THE LEVEL OF THE SEA. 53 



sea- worn cliffs and caves, stratified beds of sand, gravel, and 

 clay, and, above all, by the marine exuviae which they con- 

 tain. 



The deposits thus formed must, in Scotland at least, be 

 intercalated between the two first groups in Mr De la Beche's 

 classification of rocks, viz., the modern group and the erra- 

 tic block group. We infer that they are posterior to the 

 latter, from their superposition, and that they do not belong 

 to the former, from the absence of the remains of man or 

 of works of art. The erratic block bed, which has also been 

 termed diluvium, has in Scotland received the provincial 

 name of Till It is very accurately described by Air Bald,* 

 under the name of the old alluvial cover, in his paper on 

 the coal formation of Clackmannanshire. It generally con- 

 sists of stiff unstratified clay and gravel, confusedly mixed 

 with water-worn masses, and also with angular fragments 

 of sandstone, shale, and coal, which have not suffered from 

 attrition, although comparatively soft in their structure. 

 Organic remains are excessively rare in it. Mr Bald, who 

 remarked this, afterwards found the tusk of an elephant 

 embedded in it in the excavation of the Union Canal ; but, 

 unwilling to draw an important inference from a solitary 

 fact, he supposed it might have been placed in the situation 

 in which it was found, from some accidental cause. Since 

 that time, however, elephants 1 bones and tusks have been 

 found near Kilmarnock, and at Kilmaurs, in Ayrshire. I 

 am assured by Dr Scouler of the Royal Society of Dublin, 

 and Dr Cowper of the University of Glasgow, who visited 

 these localities, that, in both instances, they were embedded 

 in the till. At Kilmaurs they were associated with sea- 

 shells ; and, on one occasion, I also found shells embedded 



* Wern. Mem. vol. i. p. 481 ; vol. iii. p. 126. 



