192 The American. Geologist. September, 1893 
sure of the ice weight, supplemented in some degree by its friction and 
by the slowly escaping internal heat of the earth, caused the base of 
the ice-sheet under its thick central part to be melted, so that the ice 
there rested on a cushion of water, in which no erosion of the under- 
lying rock or drift was possible. Upon the area near the ice border, 
where it was too thin to be basally melted by its own pressure, glacial 
wearing and mingling of the drift took place; and in the critical area 
dividing this tract from the water-cushioned ice the drumlins, "mo6t 
puzzling of all glacial deposits," are supposed to have been accumu- 
lated. During the growth of the ice-sheet and again during its decline, 
all portions of its area would be for some time subjected to its erosion, 
mixing, transportation and deposition of drift. Though few glacialists 
and physicists will probably agree with the hypothesis of pressure 
melting, all will find much of profitable suggestion in this elaborate 
and interesting investigation. 
The Wanderings of the North Pole. By Robert S. Ball. Fort- 
nightly Review, new series, vol. liv, pp. 171-183; Aug., 1893. The invest- 
igations of Dr. S. C. Chandler are accepted as an adequate explanation 
of the small observed variations of latitude, referring them to a revolution 
of the earth's pole during a period of 127 days, the maximum circle which 
it describes in its "wanderings"' having a radius of about 30 feet. No 
appreciable secular variation is discovered, and the place of the pole 
since the Glacial period and from even earlier geologic times is believed 
to have been without greater changes than would lie inside the area of 
a block or square enclosed by the intersecting streets of a city. 
The Improvement of Geographical Teaching. By William Morris 
Davis. National Geographic Magazine, vol. v, pp. 68-75; July 10, 1893. 
The purpose of the teacher and text-book of geography, as professor 
Davis urges, should be not simply to describe the forms of the land but 
to recognize their dependence on geologic structure and erosion. An 
illustrative example is the gently inclined plateau of southern New Eng- 
land, which is shown to have been formerly a peneplain, worn down by 
subaerial denudation to a surface of moderate relief and subsequently 
tilted so that its southeastern part now sinks below the sea level, while 
northward and westward it rises to a hight about 1,500 feet above the 
sea. This plateau, much eroded and incised by streams, forms the Berk- 
shire hills in western Massachusetts and the prominently hilly south- 
western part of New Hampshire. Above its expanse, which is seen to 
have nearly uniform and apparently continuous crest lines when exam- 
ined in a broad distant view, isolated mountains, as Wachusett and 
Monadnock, rise here and there 1,000 to 1,500 feet higher, being rem- 
nants of the ancient land whose base-levelling produced the peneplain. 
For this class of mountain forms Davis suggests that the term "monad- 
nock" may be advantageously used as a generic name. Many other ex- 
amples of the geologic development of geographic forms are cited, and 
state geologists are requested to aid the school teacher by devoting por- 
tions of their field work, study and reports to this subject. 
Illustrations of the Fauna of the St. John Group. No. vn. By G. 
