208 



SIGNS OF ICE-ACTION IN TEETIAEY TIMES. 



[Ch. X. 



had one of their sides polished, in a manner much resembling 

 that produced by glacial action. The whole thickness of the 

 beds through which these blocks are dispersed varies from 100 

 to 150 feet. As yet they have yielded no organic remains, but 

 they are covered by strata containing shells of the Upper 

 Miocene formation, and they rest on Lower Miocene strata 

 for the most part of freshwater origin. The fauna and flora, 

 both of the overlying and underlying rocks, have the same sub- 

 tropical character as that of Miocene date in Switzerland and 

 in Central Europe generally. Hence the hypothesis of the 

 transport of such huge blocks by ice-action has naturally 

 been resorted to most unwillingly, but in the present state of 

 our knowledge it is the only one which appears tenable. The 

 beds of sandstone alternating with those in which the blocks 

 are enveloped exhibit no signs of having been tumultuously 

 accumulated as by a flood. The erratics seem rather to have 

 fallen quietly into their places. The nearest spots where any 

 similar serpentine and greenstone occur are about twenty miles 

 to the westward, but there has been so much subsidence of the 

 country during the Miocene period, so much subsequent depo- 

 sition of overlying miocene, pliocene, and alluvial deposits, and 

 such changes in physical geography, that we cannot form any 

 probable conjecture as to the proximity or distance of the spots 

 from which the blocks may have come. The absence of organic 

 remains may possibly imply a sea chilled by floating ice, or 

 by a cold current from the north ; but such an hypothesis is 

 not very satisfactory, because the thickness attained by the 

 conglomerate in some parts of Piedmont is very great, far ex- 



We must con- 

 clude, therefore, that its accumulation occupied a great lapse 



ceeding that seen in the vicinity of Turin. 



of time, and if so, it is difficult to understand why there are 

 no organic remains in it : for although the temporary influx 

 of a cold current might well be supposed to annihilate a 

 fauna fitted for a warmer sea, yet the long continuance of 

 such a current would naturally fit the region for species such 

 as thrive in the seas of colder latitudes. Perhaps a lofty 

 mountain, with a glacier reaching the sea, would be the 

 least objectionable hypothesis, since in Patagonia there is a 

 glacier descending from the Andes in Eyre Sound, in the 











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