CHAP. VII.] 
THE GLACIAL EPOCH. 
115 
pachyderms, and of such a littoral Lusitanian fauna as that of 
the Selsea bed where it is mixed up with the remains of some 
of those pachyderms, as well as of some other features, it has 
seemed to me that the climate of the earlier part of the post- 
glacial period in England was possibly even warmer than our 
present climate ; and that it was succeeded by a refrigeration 
sufficiently severe to cause ice to form all round our coasts, and 
glaciers to accumulate in the valleys of the mountain districts ; 
and that this increased severity of climate was preceded, and 
partially accompanied, by a limited submergence, which no- 
where apparently exceeded 300 feet, and reached that amount 
only in the northern counties of England.” 1 This decided 
admission of an alternation of warm and cold climates since the 
height of the glacial epoch by so cautious a geologist as Mr. 
Wood is very important, as is his statement of an accompanying 
depression of the land, accompanying the increased cold, because 
many geologists maintain that a greater elevation of the land is 
the true and sufficient explanation of glacial periods. 
Further evidence of this alternation is found both in the 
Isle of Man and in Ireland, where two distinct boulder clays 
have been described with intervening beds of gravels and sands. 
Palceontological evidence of alternate Cold and Warm periods . — 
Especially suggestive of a period warmer than the present, im- 
mediately following glacial conditions, is the occurrence of the 
hippopotamus in caves, brick-earths, and gravels of palaeolithic 
age. Entire skeletons of this animal have been found at Leeds 
in a bed of dark blue clay overlaid by gravel. Further north, at 
Kirkdale cave, in N. Lat. 54°. 15', remains of the hippopotamus 
occur abundantly along with those of the ox, elephant, horse, 
and other quadrupeds, and with countless remains of the 
hyaenas which devoured them ; while it has also been found 
in cave deposits in Glamorganshire, at Durdham Down, near 
Bristol, and in the post-Pliocene drifts of Dorsetshire. It is im- 
portant to note that where it is associated with other mammals 
in caves — which are hyaena-dens, and not mere receptacles of 
water-carried remains — these always imply a mild climate, the 
elephant and rhinoceros found with it being species character- 
1 Geological Magazine , 1876, p. 396. 
I 2 
