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WADORE 
[APRIL 15, 1897 
THE GLACIERS OF NORTH AMERICA. 
Glaciers of North America: a Reading Lesson for 
Students of Geography and Geology. By Israel C. 
Russell, Professor of Geology, University of Michigan, 
Pp. x + 210. (Boston, U.S.A., and London: Ginn 
and Co., 1897.) 
GOOD summary, in a convenient form, of what 
has been ascertained about North American 
glaciers, has been for some time a desideratum. Prof. 
I. C. Russell has supplied it in a volume of moderate 
size, well illustrated, and written in a cautious and 
critical spirit. As he points out in his opening words, 
North America, in reality, affords more favourable con- 
ditions for the study of existing glaciers and the records 
of ancient ice-sheets than any other continent. It affords 
excellent examples of the three types into which glaciers 
may be distinguished—namely, Alpine, Piedmont, and 
Continental. Of the first, specimens are abundant in the 
mountain system of the West, from “ pocket editions ” in 
the peaks of the High Sierra to the huge Seward glacier in 
Alaska. The latter region also supplies good instances 
of the Piedmont type, in which, as the name implies, the 
ice-streams of mountain valleys become confluent on a 
lowland ; while Greenland is a grand case of the “ Con- 
tinental” ice-sheet. Of each of these types Prof. Russell 
gives careful and lucid descriptions, in the course of 
which he notices or discusses the more important 
phenomena of ice action. We must confine ourselves to 
mentioning only two or three, which bear more especially 
on general questions. We observe that he draws a dis- 
tinction between osars and kames, applying the former 
term to continuous ridges, often many miles long ; the 
latter to irregular hills with basins between. Both are 
mainly composed of water-worn materials, and are con- 
nected with ice-sheets ; both exhibit stratification, more 
or less oblique and cross-bedded ; on the surface of both 
large angular blocks have often been dropped, but the 
osar, he thinks, has been formed by streams flowing in 
sub-glacial channels ; the kames, by deposition in cavi- 
ties beneath the ice or in open channels on its margin. 
Prof. Russell also gives an excellent account of drumlins, 
those curious elongated mounds, mainly composed of 
“till,” which are among the ice-age puzzles. Of these he 
suggests as a “working hypothesis” the following ex- 
planation. Débris embedded in an ice-sheet tends to im- 
pede its movement. If, then, any portion of the latter, 
owing tolocal causes, contains an exceptional amount of 
adventitious material, it may behave in some respects asa 
large boulder (which, however, is gradually stretched 
out), the purer ice flowing past and around it. Then at 
last it may be stranded near the end of the sheet. The 
contained ice slowly melts, and leaves behind an 
elongated mound of “till.” The hypothesis explains several 
facts, but is not without its own difficulties, on which, 
however, we must not enlarge. It is certainly ingenious, 
and it deserves careful consideration. He gives an ex- 
cellent description of the Malaspina Glacier, one of the 
Piedmont type, in Alaska. In its neighbourhood marine 
shells are found embedded in a boulder deposit, high 
above sea-level. Prof. Russell does not think it necessary 
to employ an ice-sheet to bring these shells inland from 
the bed of the Pacific, and remarks that they indicate 
NO. 1433, VOL. 55] 
very considerable upheaval in quite late geological times. 
We commend this part of the volume to those glacialists 
of Britain who repudiate almost with scorn the possibility 
of an important submergence at a date so recent as the 
glacial epoch. Perhaps in future we shall hear less of 
rampant ice-sheets at Gloppa and Moel Tryfan ! 
As regards Greenland, a good summary is given of the 
observations of Peary, Nansen, Chamberlin, and others, 
as well as some excellent and extremely suggestive 
remarks about buried masses of ice in Kotzebue Sund. 
We should not, however, be quite so ready to admit the 
possibility of the central ice in the former country being 
almost as thick as its surface is high above the sea. 
Surely it more probably conceals a country similar to, 
but on a larger scale than, Scandinavia, in which case 
the watershed would be towards the middle. There is a 
very clear summary of the diverse views on glacial 
physics. Prof. Russell concludes these by an “ eclectic 
hypothesis,” in which a tinge of sarcasm, perhaps un- 
conscious, seems perceptible. May not the difficulties of 
the subject be augmented by defective knowledge and 
an imperfect terminology? Fluid and solid are necessary 
distinctions in practice and in mathematics, but we can- 
not be so sure where the border-line lies, how far it 
depends on circumstances, or even if it has a real exist- 
ence. But we must conclude. We may hesitate in 
accepting Prof. Russell’s conclusions on one or two 
points, but not in heartily thanking him for this clearly- 
written volume, which ought to find a place on the book- 
shelves of every student of ice and its work. 
T. G. BONNEY. 
OUR BOOK SHELF. 
Hydraulic Machinery. By ®.G. Blaine. Pp. vili + 383. 
(London: E. and F. N. Spon, Ltd., 1897.) 
THE term hydraulic machinery is generally confined to 
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brakes. The book is illustrated by 272 clear figures and 
diagrams in the text, and is provided with a suitable 
