Date of the Glacial and the Upper Miocene Period. 3G5 



upon it. This sort of evidence, when found in low latitudes, 

 ought to be received as conclusive of the existence of former gla- 

 cial epochs, and, no doubt, would have been so received had it 

 not been for the idea that, if these blocks had been transported 

 by ice, there ought in addition to have been found striated 

 stones, boulder-clay, and other indications of the agency of 

 land-ice. 



The reason why we now have, comparatively speaking, so little 

 direct evidence of the existence of former glacial periods will be 

 more forcibly impressed upon the mind, if we reflect on how 

 difficult it would be in a million or so of years hence to find any 

 trace of what we now call the glacial epoch. The striated stones 

 would by that time be all, or nearly all disintegrated, and the 

 till washed away and deposited in the bottom of the sea as stra- 

 tified sands and clays. And when these became consolidated 

 into rock and were raised into dry land, the only evidence that 

 we should probably then have that there ever had been a glacial 

 epoch would be the presence of large blocks of the older rocks, 

 which would be found imbedded in the upraised formation. We 

 could only infer that there had been ice at work from the fact 

 that by no other known agency could we conceive such blocks 

 to have been transported and dropped in a still sea. 



Probably few geologists believe that during the Middle Eocene 

 and the Upper Miocene periods our country passed through a 

 condition of glaciation as severe as it has done during the Post- 

 pliocene period ; yet when we examine the subject carefully, we 

 find that there is actually no just ground to conclude that it has 

 not. For in all probability, in the strata formed out of the de- 

 struction of the now existing land-surfaces, evidence of ice-action 

 will be as scarce as in the Eocene or Miocene strata. 



If the stratified rocks forming the earth's crust consisted of a 

 series of old land-surfaces instead (as they actually do) of a series 

 of old sea-bottoms, then probably dozens of glacial periods might 

 be detected. 



Nearly all the evidence which we have regarding the glacial 

 epoch has been derived from what we find on the now ex- 

 isting land-surfaces of the globe. But probably not a trace of 

 this will be found in the stratified beds of future ages, formed 

 out of the destruction of the present land-surfaces. Even the 

 very arctic shell-beds themselves, which have afforded to the geo- 

 logist such clear proofs of a frozen sea during the glacial epoch, 

 will not be found in those stratified rocks; for they must suffer 

 destruction along with everything else which now exists above 

 the sea-level. There is probably not a single relic of the glacial 

 epoch which has ever been seen by the eye of man that will be 

 found in the stratified rocks of future ages. Nothing but what 



