* 
438 J. Croll—Examination of Wallace’s Modification of the 
perihelion, is as much a necessary result as a cold and glacial 
condition when they occur in aphelion. 
The facts of Geology thus to me appear so far to be as much 
cpp to Mr. Wallace’s modifications as are the principles of 
hysies. 
ifficulty in detecting the Climatic Character of the earlier 
Interglacial Periods.—I\t follows according to theory that, other 
things being equal, the greater the amount of eccentricity the 
more equable and mild will the interglacial periods be. It is 
probable therefore that some of the earlier interglactal periods 
were milder and more equable than the last. It may be difficult 
in the present state of our knowledge to prove this conclusion 
glacial periods have been preserved is a conclusion which we 
eo We: ese beyond the limits reached by the ice-sheets 
of the Glacial Epoch we may expect, of course, to find the 
remains of many of the plants and animals which lived during 
the probability is that they would be classified as preglacial. “ 
I fully agree with Prof. J. Geikie, that many. of those plan's 
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