Revieiv of Recent Geological Literature. 57 
polar axis, and in the orbital eccentricity of the earth. Some 
of these are beyond the range of analysis and investigation, 
and others are of local and minor influence, and may be left 
out of consideration in a discussion of the fundamental prin- 
ciples. 
If the eras of climatic evolution which our planet has un- 
dergone have herein been referred to their proper laws and 
sequence, the questions involved may not be the fearful 
"glacial nightmare" that some would make them; but rather 
the means whereby we recognize the Ice age as one of these 
eras, during which the land areas were made smoother and 
more stable, and the soils more uniform in composition and 
fertility. 
If new light has been thrown on the grand problems of 
terrestrial physics, much remains to be done. The worship- 
ers who bow at the altars of science will have a stronger 
faith to cheer them on; and if some of their early structures 
have been rudely struck, it is hoped that in their stead grander 
and more stately temples will be reared whose foundations 
rest upon everlasting truth. 
REVIEW OF RECENT GEOLOGICAL 
LITERATURE. 
Fossil Medusa. By C. D. Walcott. (U. S. Geol. Surv. Mono- 
graphs. Vol. XXX, Washington, 1898.) 
This magnificent volume, so thorough in its treatment of the sub- 
ject, and so profusely illustrated, is a most valuable gift of the U. S. 
Geological Survey to the scientific world. 
Fortunately as the known fossils of the Medusae are comparatively 
few, Mr. Walcott has been able to present in this volume a complete 
review of the organic remains of this order hitherto found in the 
Paleozoic and Mesozoic rocks. 
The fossil Medusae so far discovered belong chiefly to the Cam- 
brian and the Jurassic systems, and to these the memoir is almost 
entirely devoted. They have been found mostly at two points in the 
Appalachian range in America and in Sweden and Bavaria in Europe. 
About one-half of the text of this memoir is devoted to a description 
of the former, and the second half to a reproduction of the accounts, 
scattered in several periodicals, etc., which describe the European 
Medusae. 
