Beriew of Recoif GeolofficaJ Literature. 45 
Champlain depression of the land and incursion of the sea. from which 
the country has been since uplifted to a maximum hight exceeding 500 
feet, make it difficult to accept the theory which attributes all the drift 
to land ice. The arguments on both sides are well stated by Prof. Bon- 
ney, who evidently inclines toward a compound explanation, nearly like 
that of Sir William Dawson. The depositsof stratified or modified drift, 
enclosing marine shells, mostly fragmentary, on Moel Tryfaen, and at 
Macclesfield, Gloppa, and other localities, extending in northern Wales 
and northwestern England up 1,100 to 1,400 feet above the sea level, 
and about 500 feet at Clava in Scotland (Am. Geologist, vol. xvii, pp. 
45-47, Jan., 1896), are regarded as strong evidence of a Late Glacial or 
Champlain marine submergence to these amounts. Similarly, the 
Parallel Roads of Glen Roy are thought to be best explained as marine 
shore lines, although Jamieson, in the latest important paper on that 
subject, shows how they may be referred to successive stages of a glacial 
lake held by the waning Scottish ice-sheet, — a much better explanation 
than was formerly found in fluctuations of local valley glaciers. 
The title of this book well indicates its chief purpose, which is a com- 
jjarison of present and now observable ice action in eroding, transport- 
ing, and depositing drift, with the past agencies of striation of the 
bed-rocks, and accumulation of drumlins, other deposits of till or 
boulder-clay, marginal moraines, kames, eskers, and all the forms of the 
glacial and modified drift, together with discussion of its previous sub- 
glacial and englacial transportation. A large share of attention is 
given to the drift formations of North America, and these are illustrated 
by maps and views. The causes of the Ice age are discussed, but with- 
out expressing confidence in any of the current theories ; nor is a de- 
cision rendered on the vexed question whether there were successive 
and independent epochs of glaciation during the Pleistocene period. 
From all the earlier geologic record Prof. Bonney finds evidence of only 
one other time of widely extended glaciation, this being late in the 
Carboniferous or early in the Permian period. The I'leistocene glaci- 
ation he would refer to a moderate refrigeration of the drift-bearing 
areas, not necessarily exceeding 12° to 20°, and pei-haps even no more 
than 8'^ or 6° in New Zealand. 
In general, for North America and Europe, the best explanation of 
the glacial conditions is apparently thought by Prof. Bonney to be the 
accunmlation of large ice-sheets on much elevated central areas whence 
they are supposed to have flowed outward to terminate on lowlands. 
The present reviewer, however, would suggest that the preglacial eleva- 
tion inducing the snowfall and ice accumulation probably included, in 
variable but everywhere large amount of epeirogenic uplift, all the 
drift-bearing regions of both continents, the elevation of their peripheral 
portions being measured approximately by the depth of fjords and the 
continuation of river valleys, as of the Hudson river southeast of New 
York city, which descends 2,800 feet beneath the sea level. 
Another volume, to cover similar ground as this, is earnestly hoped 
for by working glacialists, in which I'rof. Chaml)er!iii may bring to- 
