438 Climate of the Glacial Period. (October, 
this paper, in future years, they will think many of 
my arguments unnecessary and superfluous; but my con- 
temporaries know what a large amount of acceptance this 
theory has met with amongst our leading scientific men, 
many of whom have adopted it as the true cause of the 
Glacial period. What is required, therefore, at the 
present time, is a thoroughly exhaustive examination of 
it, and to the best of my ability I shall make it. 
The most complete geological evidence is that of the 
marine shells. They have been more certainly and abun- 
dantly preserved than other organisms, and from the 
earliest Tertiary epoch up to the present time we have an 
almost continuous series illustrating the successive faunas, 
and in the interglacial beds they have been much studied. I 
shall now take the evidence that these last afford us into 
consideration, and that nothing may be overlooked I shall 
take my examples from the ‘‘ Great Ice Age” of Mr. James 
Geikie, who is one of Mr. Croll’s most ardent supporters. 
First of all, we may dismiss all the Scotch interglacial beds 
as negatively hostile to the theory, as they either contain no 
organisms at all, or—in a few cases—some shells of arétic 
types; nowhere have more southern forms been found than 
those existing off the present coasts. Coming to England, 
we have the marine shells of the west coast interglacial 
beds,—those found on Moel ‘Twyfaen, at Macclesfield, and 
generally over South Lancashire. I have, in another 
place, argued that these shells are of older date than the 
Glacial period, and that they were pushed up out of the bed 
of the Irish Sea by the great glacier that filled it;* but I 
need not go into this argument here, as, whatever the evi- 
dence may be worth, it is again hostile, and Mr. Geikie 
admits that ‘‘ upon the whole the fossils indicate colder con- 
ditions than now obtain in the [rish Sea.”t On the eastern 
coast most of the shells that have been found indicate a 
colder climate, but at Holderness a few fragments of more 
southern species have been discovered. Messrs. Wood and 
Harmer, who have described these deposits, admit that they 
have been transported from some other area; and Mr. Croll 
has himself, with great acumen, shown how they might have 
been pushed up out of the German Ocean by the ice that 
brought over blocks of stone from Scandinavia and thrust 
them up on the same coast. However, whether brought by 
currents of water, as suggested by Messrs. Wood and 
* Nature, vol. x., pp. 25 and 62. 
+t Great Ice Age, p. 362. 
