80 M. Stirrup — True Horizon of the Mammoth. 



to strengthen this conclusion : the negative one, viz. the absence 

 of any evidence of Paleolithic Man over the areas covered by the 

 Glacial Drift ; and the positive evidence of the amelioration of 

 the climate of Western Europe at the close of the Glacial epoch, 

 corresponding to the amelioration of climate which characterized 

 the end of the Palaeolithic age and the advent of Neolithic Man. 

 The retreat of the Boreal Mollusca northwards at the close of the 

 deposition of the Drift is a very significant fact if it be considered in 

 conjunction with the dispersion of the Mammalia northwards and 

 Alpwards at the termination of the Palaeolithic age. 



In considering the relations of Britain to the events of the Glacial 

 epoch, it should be borne in mind that our Island was situated on 

 the confines of that portion of the Northern Hemisphere which 

 suffered glaciation. It was one of the last places the ice-sheet 

 reached, and one of the first from which it retreated. The supposed 

 great time required for the formation of the Glacial Drift and the 

 post-Glacial deposits has blocked the way to any successful attempt 

 to synchronize the Drift with the older river and cave deposits, 

 containing the relics of Palgeolithic Man and his Mammalian con- 

 temporaries. There are, however, no internal evidences in the Drift 

 deposits indicative of any great antiquity. We frequently find them 

 resting upon glaciated surfaces so perfectly polished, and with 

 delicate strise so exquisitely preserved, that it might have been 

 but yesterday that the glacier which caused them had retreated, 

 and not, as some affirm it to have been, thousands of years ago. 

 Then, if we examine the Boulder-clay we meet with Foraminifera 

 embedded in it, yet despite their long emtombment their shells 

 show no signs of decay. 



The Drift rarely exceeds 300 feet in thickness. If it were formed 

 at the rate of a quarter of an inch per annum, a little over 15,000 

 years would suffice for its accumulation. 



We possess, of course, no geological data for the foregoing or any 

 other geological calculation of the measure of the duration of the 

 time represented by the Glacial Drift. Therefore, no reasonable 

 objection on the ground of the great lapse of time required for the 

 formation of Glacial and post-Glacial strata can be taken against 

 synchronizing the Palaeolithic age with the Glacial Drift, and 

 Neolithic Man with post-Glacial times. 



*" Query : " felstone," for which see Prof. Hughes' most interesting 

 paper upon the "Drifts of the Vale of Clwyd" (Q.J.G.S. vol. xliii. 

 p. 107). It is quite immaterial, however, to the argument, whether 

 the implements found in the " Pont Newydd " cave were composed 

 of "quartzite" or "felstone," as both rocks would have been equally 

 accessible. 



VII. — The True Horizon of the Mammoth 

 By Mark Stirrup, F.G.S. 



IN the abstract of the proceedings of the meeting, on November 

 8th, of the Geological Society of London, I notice that on 

 the reading of Dr. G. M. Dawson's " Notes on the occurrence of 



