^^^ Geological Society. 



other hard trap rocks near Edinburgh, many of which have been de- 

 scribed and attributed to diluvial action by Sir James Hall. 



In Northumberland Dr. Buckland describes an immense accu- 

 mulation of morains, or detritus of morains, at the east base of the 

 Cheviots, near Wooler; and in the lake districts of Cumberland 

 and Westmoreland he found the sides of many mountain valleys 

 and gorges, by which the waters of these lakes have their exit to the 

 adjacent plains, to bear marks similar to those produced by glaciers, 

 viz. rounded, striated and polished surfaces, accompanied by the 

 accumulation of mounds of gravel and erratic blocks in the low 

 countries subjacent to them. 



Mr. Lyell has read a paper on the evidences of the action of ice 

 in Forfarshire, and has re-examined that county in order to satisfy 

 himself whether the boulder formation of the district, which he had 

 previously regarded as the effect of drift-ice on submerged land, might 

 be explained by the agency of ice acting on land already elevated 

 above the sea. This latter conclusion he is now inclined to adopt, 

 believing that it is favoured by the mounds of transported materials 

 bearing the form of morains, and for the most part unstratified, 

 which occur on the sides of almost every valley in the Grampians, and 

 sometimes across the glens ?it right di.ng\e&, and almost blocking them 

 up. He finds this opinion further confirmed by the local distribution 

 of rocky fragments, and the evidence of their descent from higher 

 to lower levels ; and, lastly, he thinks that the rarity of organic re- 

 mains in the till or boulder clay lends support to the same view. 

 He mentions several deep lakes in the Grampians in Forfarshire, on 

 the lower sides of which enormous accumulations of mud, gravel 

 and angular blocks are strewed, which are derived from precipices 

 on their higher side ; these materials would have filled up the lakes, 

 unless we suppose them to have been formerly occupied by ice. 



The effects of drift-ice in producing alternations of stratified and 

 unstratified deposits, and in causing curvatures in strata of sand and 

 gravel, while underlying beds remain horizontal and undisturbed, 

 were treated of last year by Mr. Lyell in a paper on the mud-cliffs of 

 Norfolk. But in Forfarshire the till, or unstratified matter containing 

 boulders and angular blocks, is found everywhere underlying the 

 stratified sand and clay ; had the whole deposit been accumulated 

 under water, we might have expected alternations ; Mr. Lyell there- 

 fore conjectures that the older till may have been formed in great 

 part when the glaciers were gradually advancing over the country, 

 at the period of the first coming on of a colder climate, and that 

 portions of the morains may have become subsequently stratified 

 in temporary lakes, or during floods in those valleys where sti'atifi- 

 cation is observable. 



Another feature in the distribution of the transported materials of 

 Forfarshire and Perthshire is a contiimous stream, from three to three 

 and a half miles wide, of boulders and pebbles, traceable from near 

 Dunkeld by Coupar and the south of Blairgowrie into Strathuiore,and 

 thence in a straight line through the lowest depression of the Sid- 

 law hills from Forfar to Lunan Bay, a distance of thirty-four miles. 



