270 Reviews—Howse on Glaciation in N. Britain. 
Further on (p. 182) we find the following passage :-— 
‘For it is necessary, in order to account for the deposition of the Boulder- 
clay, and the beds of clay, sand, and gravel which occur all over these 
counties, to assume that the whole, or nearly so, of the entire island was 
submerged beneath the sea. It was during this period of submergence that 
the Boulder-clay was deposited . . . . Can we doubt, when we look at the 
surface of the country, that the numerous isolated hills formed at this period 
numerous small islands, which were in their turn submerged, and covered 
with deposits still brought down from the west on floating masses of ice 
detached from the glacier-face of the upper valley ?’ 
Again, at p. 184 :— 
‘The theory of stranded icebergs, and masses of floating ice drifting 
along the coast-line, is quite insufficient, and entirely inadequate to produce 
the appearances above enumerated; for it is pretty clear that these rocks 
were glaciated and covered with a thick deposit of Boulder-clay before the 
land was submerged deep enough for icebergs to pass over them,’ 
The subject itself is undoubtedly one of great difficulty ; and only 
continued steady examination of ice-worn and drift-laden districts, 
with a clear comprehension of the meaning of the phenomena, 
elucidated by our slowly advancing knowledge of ice-action under 
manifold conditions, can be expected to make us masters in this 
branch of geology. 
On THE CONFORMATION OF THE ALps. By Joun Tynpatt, F.R.S., 
&c. (Phil. Mag., October, 1864, pp. 255-271.) 
On THE EROSION OF VALLEYS AND LAKES; A REPLY TO SiR 
Roperick Murcuison’s ANNIVERSARY ADDRESS TO THE GEO- 
GRAPHICAL Society. By A. C. Ramsay, F.R.S. (Phil. Mag., 
October, 1864, pp. 293-311.) 
(pee is no question at present under discussion among geo- . 
logists so important as that relating to the value of existing 
causes of change; and one branch of this subject is treated in the 
two able and interesting articles now before us. They both treat, 
though in a different way, of the action of water—liquid and solid, 
as an agent in the production of the surface-phenomena of the globe. 
They both support the view that to the slow, but long enduring, 
mechanical power of water, rather than to any convulsive throes or 
violent disruptions, are due those grand, striking, and exceptional 
phenomena seen in perfection in the Western Alps. ‘They refer to 
erosion as the one great cause of the most picturesque features of 
that noble mountain-chain,—its deep and narrow gorges, its moun- 
tain-valleys, and even its large and beautiful lakes. They communi- 
cate the experience of men, one an accomplished student of the 
physical sciences, who is exceedingly familiar with ice and its 
results,—the other an experienced practical geologist, who has 
observed much in his own country, and who is not without a personal 
knowledge of Switzerland. The questions they discuss are rendered 
yet more interesting at the present moment, because the veteran 
champion of the opposite school of geology,—that which assumes 
