830 The American Naturalist. ` [September, 
time favor us with a volume on the advances made during this period 
also. ; 
“The Glacial Nightmare and the Flood. ”™—To American 
geologists, the title of this work is almost a challenge, and might cause 
it to be ignored, but to every student of superficial geology it is an in- 
valuable book. It is a well-arranged history of the observations and 
growth of the science of superficial geology. To many of the fathers of 
this department of science, it is a tardy justice, and impresses a fair 
reader with the vast array of facts which were collected at an early 
date, not in Europe alone, but also in America, leaving for the later 
observers far less new work than our modern writers usually recognize. 
Another lesson taught demonstrates that the generalized conclusions of 
the greatest idols of science are by no means established, and often retard 
progress. The teachings of each succeeding generation replace, to some 
extent, those of the preceding, until at last reaction sets in and separ- 
ates the chaff and shows us how much the early scientific geniuses did 
for their science, though, perhaps, drawn off into erroneous by-ways. 
The work fairly sets forth the rise of the doctrine of tloods and its 
abandonment; of the growth and limitation of the iceberg theory; of 
the origin and culmination of the glacial theory, with Schimper at the 
head, and originating the term Ice Age. Thus far the author’s hand is 
hardly seen in the book. The treatise is of special value in systematic- 
ally bringing together the facts and views and doing justice to the 
authors of works, many of which have been overlooked or are not 
accessible to American geologists. 
On the subject of the unity of the glacial period the evidence is fairly 
stated, but the author marshalls an array of data favoring the unity of 
the Age in its general aspect, a point upon which American glacialists 
differ. The difficulties in accepting the astronomical causes of the Ice 
Age are fairly set forth, and these adverse conclusions will be received 
by most American geologists. The cause of glacier motions, and the 
mechanical effects of glaciers are discussed from their physical aspects, 
and appear very satisfactory to most observers. The facts showing the 
former extension of glaciers are arranged, and show how the ice-cap 
theory has given place to continental glaciers. But here the work is 
directed against the extreme views, giving rise to the title of the 
book, on the ground of lack of evidence, and challenges the right of 
1 By Sir Henry H. Howarth, K. C. I. E., M. P., F. G. S., ete. 2 vol. pp. l- 
920. Sampson, Low, Marston & Company, London. 
