CROLDS " CLIMATE AND TIME:' 823 



Besides, such a collocation affords a sufficient period for the develop- 

 ment of the rich and characteristic fauna and flora of the forest-bed — 

 a widespread fossiliferous and carbonaceous deposit that must repre- 

 sent a lapse of time of geological importance. The belief that any 

 glacier would necessarily remove all the debris formed by an ante- 

 cedent one — a belief "which has done much to prevent the acceptance 

 of theories of successive glaciation — is best shown to be fallacious by 

 the unequivocal evidence that the ice of the last glacial epoch did pass 

 over older deposits of unconsolidated materials without removing 

 them. Some such evidence is cited by Dr. Croll in the last-named 

 chapters. 



Among the interesting cognate subjects taken up in the remaining 

 eleven chapters of the work are — methods of measuring the rate of 

 subaerial denudation, and of determining the mean thickness of the 

 rocks of the globe ; the age and origin of the sun (which is an able 

 effort to reconcile the existing disagreement between the geologist 

 and the astronomer and physicist as to the age of the earth) ; the 

 physical cause of continental submergence and emergence during the 

 glacial period ; the influence of the obliquity of the ecliptic on ter- 

 restrial climate ; some glacial phenomena of Scotland and England ; 

 and the physical cause of glacier-motion. Appendices and an index 

 are added. 



It has been the aim in the foregoing pages to convey a general idea 

 of the nature and scope of the work under review, and at the same 

 time to indicate those points which do not seem to be sustained ; and, 

 as is natural in view of this double object, justice has not been done 

 to the work as a whole. " Climate and Time " represents years of 

 study and an almost incredible amount of conscientious labor by per- 

 haps the most competent living man to deal with this obscure subject, 

 which occupies a position intermediate betAveen geology, physics, and 

 astronomy, and requires a thorough knowledge o'f all of these branches 

 of science for its adequate comprehension. As a geologist, Dr. Croll 

 occupies an important and responsible position ; and, as an astronomer 

 and physicist, his reputation in scientific circles is even more enviable. 

 Owing to the confusion in which he found the subject, to the absence 

 of reliable data, and perhaps to a rather radical disposition, he seems 

 to have fallen into a few errors ; but, with some reservations, his in- 

 genious theory has been received with much favor, and has been pretty 

 widely adopted, especially on the other side of the Atlantic. Here, it 

 is comparatively unknown, and, in too many cases, lack of acquaintance 

 Avith the principles on which it is based has led to its being unfavora- 

 bly regarded ; but even those who reject the theory would do well to 

 familiarize themselves with its details before they undertake to inves- 

 tigate the subject anew. 



