188 REVIEWS 
closing chapter, xxv, is devoted to a study of the relation of surface features 
to geologic structures. 
Throughout the volume Mr. Geikie has limited himself to the more 
settled doctrines and principles of working geology, and has not attempted 
to present alternative views or possible objections. He has avoided the 
presentation of many of the problems now engaging the attention of struc- 
tural geologists. 
The photographic illustrations deserve special mention for their excel- 
lence, and among them the photographs of rock specimens are the most 
remarkable. 
W. W. ATwoopD 
The Viscous vs. the Granular Theory of Glacial Motion. By Oswin 
W. Wittcox. Long Branch, N. J.: Published by the author, 
1900. Eps 22% 
This is less a treatment of the theme implied by the title than a review 
ofa particular statement of one phase of the granular theory.! Even as 
a special criticism it goes wide of the mark, as the author, inadvertently it 
is to be assumed, substitutes easily demolished propositions of his own for 
those of the sponsors of the granular theory. As the leading feature of his 
discussion, Dr. Willcox attributes to the special sponsor he selects the 
unlimited proposition that ‘‘strictly crystalline minerals are incapable of 
manifesting viscous fluidity,”’ whereas the real proposition is the very 
special one that ‘‘the retention of its crystalline structure,” by the ice 
granule, during glacial motion, is incompatible with a viscous flowage of 
the granule. The ‘“‘universal principle” thus substituted for the special 
proposition is attacked by the citation of the peculiar phenomena mani- 
fested by certain organic compounds, called, with more or less questionable 
propriety, “crystalline liquids” and ‘‘liquid crystals.” These interesting 
phenomena have been all along known to some of the sponsors of the 
granular theory, presumably to all, and have awakened the question 
whether these “‘liquid crystals” are not short of being typical liquids to 
the extent that they are “crystalline,” and short of being typically ‘“‘crys- 
talline” to the extent that they are liquids. The more vital question, 
however, is whether or not they retain their ‘‘crystalline” character while 
undergoing continuous and protracted motion under stress. Had these ques- 
tions been sharply discussed, with full and critical data, the contribution 
would have been at least suggestive as to theoretical possibilities of beha- 
‘Chamberlin, A Contribution to the Theory of Glacial Motion, University of 
Chicago Press, 1904. 
