1867.] CROSSKEY — ON GLACIAL DEPOSITS. 209 



during the glacial epoch, so little different from that now prevailing, 

 while in Scotland the contrast has been so extreme. 



II. Another most important point connected with the Canadian 

 glacial beds, as compared with those of Scotland, is that they 

 occur in a distinct order, whereas in the Clyde district, their order 

 is only a matter of inference. 



Dr. Dawson gives some instructive sections. In the lower beds 

 are the deep water fossils, while littoral species occur in ascending 

 order, manifesting the gradual alteration of the old sea bottom. 



In collections of Clyde fossil shells we have a mixture of deep- 

 sea coralline, laminarian, and littoral species ; but while we have 

 superimposed beaches, we have no orderly succession in any 

 exposed section, equivalent e.g. to that of Logan's farm, Montreal. 

 - By carefully collecting the fossils from each separate pit in 

 Scotland, and comparing them together, it may be proved, I think, 

 that we have beds equivalent to those of Montreal, although our 

 local sections are physically more obscure. Taking our glacial 

 beds as a whole, it cannot be said that they co-existed at one 

 depth, or were even synchronous. The Canadian beds justify the 

 conviction I have long entertained and endeavoured to work out 

 in the field, that our clay beds can be classified, and that there 

 exists a definite order to reward patient research. They also 

 support the proofs we have accumulated in this district of the 

 theory that the rise of land was gradual, and that the passage 

 from the ice epoch to the present was accomplished by forces 

 extending over that vast period of time, necessarily demanded for 

 those very delicate changes, involved in the distribution and 

 redistribution of a specific fauna. It is not simply that a few 

 mollusca disappear from their accustomed haunts— a great deal 

 more is involved in a change of climate as it affects a fauna. 

 Zoophytes, Foraminifera, Entomdstraca, must gradually alter 

 their proportions and their specific representatives, as well as 

 mollusca, so that between any two marked points of contrast, must 

 stretch vast periods of geologic time. 



III. All our Clyde shells occur in beds, resting upon the oldest 

 boulder clay. The absolute absence of fossils, and the superposition 

 of the shell-bearing clays, are facts which prove that the old 

 boulder clays of the west of Scotland are the produce of land ice. 

 The boulder clay appears the base of the section quoted from 

 Logan's farm, just as it is of our Clyde series 



Y0L - IIL * Xo.3 



