former existence of Glaciers in Forfarshire. 579 



masses could have come in contact with the roof of a low vault. On 

 the contrary, it is easy, he says, to explain the phaenomena of the 

 polish by the long-- continued action of fragments of ice forced into 

 the cave laterally from the bottom of a glacier descending the valley, 

 on the margin of which the vault is placed ; and the irregular group- 

 ing of the parallel striae to the unequal motion of different fragments 

 of ice, charged with particles of stone firmly fixed in them, like the 

 teeth of a file. The cave is not three hundred feet above the level 

 of the sea, and the proving of glacial action at this point justifies, 

 the author states, the belief that glaciers may also at that period 

 have covered Calton Hill and the Castle Hills of Edinburgh and 

 Stirling. 



A paper " On the Geological Evidence of the former existence of 

 Glaciers in Forfarshire," by Charles Lyell, jun., Esq., F.R.S., 

 F.G.S., was commenced. 



Dec. 2. — Mr. Lyell's memoir " On the Geological Evidence of 

 the former existence of Glaciers in Forfarshire," commenced on the 

 18th of November, was concluded. 



Three classes of phaenomena connected with the transported 

 superficial detritus of Forfarshire, Mr. Lyell had referred, for several 

 years, to the action of drifting ice ; namely, 1st, the occurrence of 

 erratics or vast boulders on tbe tops and sides of hills at various 

 heights, as well as in the bottoms of the valleys, and far from the 

 parent rocks ; 2ndly, the want of stratification in the larger portion 

 of the boulder formation or till ; and 3rdly, the curvatures and con- 

 tortions of many of the incoherent .strata of gravel or of clay restmg 

 upon the unstratified till*. When, however, he attempted to apply 

 the theory of drifting ice over a submerged country to facts with 

 which he had been long acquainted in Forfarshire, he found great 

 difliculty in accounting for the constant subterposition of the till 

 with boulders to the stratified deposits of loam and gravel ; for the 

 till ascending to higher levels than the gravel, and often forming 

 mounds which nearly block up the drainage of certain glens and 

 straths ; for its constituting, with a capping of stratified matter, 

 nbirrow ridges, M'hich frequently surround lake-swamps and peat- 

 mosses ; and for the total absence of organic remains in the till. 



Since, however, Professor Agassiz's extension to Scotland of the 

 glacial theory, and its attendant phaenomena, Mr. Lyell has re-ex- 

 amined a considerable portion of Forfarshire, and having become 

 convinced that glaciers existed for a long time in the Grampians, 

 and extended into the low country, many of his previous difficulties 

 have been removed. There are, nevertheless, facts connected with 

 the ridges of stratified materials resting upon till, which he is unable 

 to exjjlain. He also states, that though he had for years inferred 

 from the evidence of fossil shells sent to him from Canada by Capt. 

 Bayfield, that the climate of North America, in the latitude of Que- 



• See Mr. Lyell's paper on tlie Norfolk Drift, Phil. Mag., May 1840, 

 [Third Series, vol. xvi. p. .'545,] and the .\bstract of the paper in the Pro- 

 ceedings of the Society, vol. ill. p. 171. 

 2 P2 



