36 Charles Maclaren, Esq., on (he Existence of 



in the Alps, p. 53, first ed.) May not this fact authorise us 

 to conclude, that the same agent which dressed and grooved 

 the bottom of Gareloch valley dressed and grooved the tops 

 of the hills on both sides of it ; and that glaciers, or moving 

 masses of ice, not only filled the hollows, but enveloped all 

 the ridges here to the height of 1500 or 2000 feet ^ There 

 are five or six ridges between the south end of Loch Eck, 

 and Luss on Loch Lomond, all nearly parallel, and running 

 transverse to the laminar structure of the mica-slate. The 

 ridge o, the southern part of fi o (Fig. 5), the whole of d7n, 

 and of ^, are examples. The straight or gently undulating 

 outline of their crests, and the evenness of their sides, con- 

 trast, in a remarkable manner, with the rugged and serrated 

 forms of the mountains to the northward, and seem to me 

 clearly to indicate that they had been subjected to abrasion, 

 by agents which either had not operated on the others, or 

 had operated very feebly. One of these smoothed hills near 

 Loch Lomond is at least 2000 feet in height. 



Cause of the Cold of the Glacial Epoch, 

 Poisson, an eminent French mathematician, proposed an 

 ingenious theory to account for the more intense cold which 

 anciently prevailed in several parts of Europe, as evinced by 

 the phenomena I have described, and many others. It has 

 been deduced from observations made by the late eminent 

 Prussian astronomer Bessel, that our sun, with the planetary 

 system attached to him, is moving through the celestial 

 spaces, in a determinate direction, at the rate of 3,800,000 

 miles per day. — [Humboldfs Cosmos, p. 152, Eng. ed.) Now, 

 as the stars, which are the sources of heat, are very unequally 

 distributed in the heavens, Poisson thought that the solar sys- 

 tem, in its journey towards the constellation Hercules, might 

 pass through spaces of very different temperatures, and that 

 at some ancient and remote period it might have passed 

 through a region of the heavens much colder than that in 

 which it is now moving. 



A much simpler explanation of the change has been pro- 

 posed by Mr Lyell. Founding on principles developed by 

 Humboldt, he observes, that the climate of any part of the 



