1850.] SMITH ON THE TILL. 387 



sea, as well as the species of the shells, and the nature of the deposit 

 in which they were found. Mr. Craig kindly accompanied me to 

 the locality, which is near the Monkland Iron Works, and about 

 fourteen miles to the south-east of Glasgow. 



The shelly deposit in question proved to be a bed of the Tellina 

 proxima. Brown (T. calcarea ?, Linn.), an arctic species, extremely 

 abundant in the Clyde pleistocene beds overlying the Till, and which 

 I had formerly procured from a Brickwork in the same neighbour- 

 hood. The shells in the present instance were discovered by Mr. 

 James Russell, an operative miner, in digging a well. 



I ascertained the elevation of the place above the summit-level of 

 the Monkland Canal, by barometrical measurement, to be 248 feet, 

 which, added to the height of the canal 276 feet, made the elevation 

 of the surface of the ground 524 feet above the high-water level of 

 the sea. 



This is at least 150 feet higher than the highest level at which 

 any shelly deposits have been hitherto discovered in Scotland, and 

 they have only been discovered so high as that level in the two fol- 

 lowing instances : Mr. Craig found shells near Airdrie*, at the esti- 

 mated height of 350 feet, and Mr. Prestwich found them at the same 

 height at Gamrie in Banfff. 



At the time when Mr. Prestwich made that discovery, it was not 

 suspected that the shells in these very modern deposits differed in 

 any respect from the shells now inhabiting the adjoining seas, and he 

 accordingly named those which he discovered after the recent species 

 which most nearly resembled them. Suspecting that a difference 

 existed, I requested leave to examine them ; having done so, I find 

 that they possess the same arctic character that the Clyde shells do, 

 and in particular, that the species which Mr. Prestwich named Tellina 

 tenuis is in fact the Tellina proxima, the same species as that found 

 on the present occasion. This is a fact of some importance, because 

 it has been supposed by many geologists that none of the shells found 

 in the raised beds in the east coast of Scotland differ from those now 

 inhabiting the adjoining sea. 



The most remarkable circumstance attending the present discovery 

 is, that the shells were imbedded in the stratified clay below the Till. 



Mr. Russell states, that at the depth of fourteen feet from the surface, 

 after passing through the Till, he came to a bed of brick clay con- 

 taining the shells, which were therefore 510 feet above the level of 

 the sea. I could entertain no doubts as to the nature of the super- 

 incumbent matter, as that part of it which had been thrown out was 

 left lying at the mouth of the well. It was unquestionably the true 

 Till. Indeed, if I had entertained any doubt as to this point, it would 

 have been removed by the discovery of a small granite boulder, which 

 was found about two feet above the bottom of the Till. I may here 

 observe, that granite boulders to the east and south of Glasgow are 

 excessively rare, and very small ; I have not seen any larger than a 



* See my paper on the Last Changes of Level in the British Islands, Mem. 

 of Wernerian Society, vol. viii. p. 59. 



t Proceedings of Geol. Soc. vol. ii. p. 545. 



