378 Mr. J. Croll on Geological Time, and the probable 



true glacial period. But in regard to the period of the true 

 boulder-clay or till, when the country was enveloped in ice, all 

 is almost, comparatively speaking, a perfect blank so far as 

 palaeontology is concerned. " Whatever may be the cause," says 

 Sir Charles Lyell, ii the fact is certain that over large areas in 

 Scotland, Ireland, and Wales, I might add throughout the north- 

 ern hemisphere on both sides of the Atlantic, the stratified drift 

 of the glacial period is very commonly devoid of fossils"*. 



In the " flysch " of the Eocenes of the Alps, in which the huge 

 blocks are found which prove the existence of ice-action during 

 that period, few or no fossils have been found. So devoid 

 of organic remains is that formation, that it is only from its 

 position, says Sir Charles, that it is known to belong to the 

 middle or " nummulitic " portion of the great Eocene series. 

 Again, in the conglomerates at Turin, belonging to the Upper- 

 Miocene period, in which the angular blocks of limestone are 

 found which prove that during that period Alpine glaciers 

 reached the sea-level in the latitude of Italy, not a single orga- 

 nic remain has been found. It would seem that an extreme 

 paucity of organic life is a characteristic of a glacial period, which 

 warrants us to conclude that the absence of organic remains in 

 any formation otherwise indicative of a cold climate cannot be 

 regarded as sufficient evidence that that formation does not 

 belong to a cold period. 



But if there is a deficiency -of direct positive evidence of a 

 general glaciation of the northern hemisphere during the Middle- 

 Eocene, Upper-Miocene, and other periods similar to what we 

 know took place during the Postpliocene period, there is, how- 

 ever, abundance of indirect evidence in favour of it. 



Those facts to which I allude that appear to lead indirectly to 

 the conclusion that a general condition of glaciation must have pre- 

 vailed during the Upper-Miocene and other periods, are, strange 

 to say, the very facts which have all along been adduced as a 

 reason against the possibility of a cold condition of climate at 

 those periods — notwithstanding the positive evidence w T hich we 

 have that the Alps and the Pyrenees t must have possessed 

 enormous glaciers during that period, those of the former reach- 

 ing the sea-level in the latitude of Italy. 



If a cold and glacial condition of climate prevailed at those 

 periods, we may be perfectly certain that a very warm and equable 

 condition of climate must have also prevailed immediately before 



* Antiquity of Man, p. 268 (third edition). 



t For an account of the evidence of a glaciation of the Pyrenees during 

 the Miocene period, see a paper " On the Glacial Phenomena of the Pyre- 

 nees," by Mr. P. W. Stuart Menteath, read before the Edinburgh Geolo- 

 gical Society, 1867. See also Bulletin de la Societe Ramond, 1866. 



