ME. T. M. READE AN ESTIMATE OP TOST-GLACIAL TIME. 297 



should be found, it will probably be below the estuarinc beds on 

 the surface of the Boulder-clay. 



There is little doubt that this surface was occupied by a fauna 

 now partially extinct ; but the subaerial conditions, which lasted so 

 great a len<?th of time, were apparently unfavourable to the preser- 

 vation of their remains. Sir Charles Lyell states that the skulls of 

 two Mammoths were taken out of the excavation made for the 

 Holyhead Railway, near the harbour, two feet below the surface of a 

 bed of peat, which was covered with stiff blue clay. This peat was 

 continuous with that exposed at low water in the harbour of Holy- 

 head, in which were seen stumps and roots of trees *. 



The basis on which we have had to construct our estimate is 

 naturally imperfect ; but against any possible overestimate of time 

 which may have crept in from the imperfection of the time-measures 

 applied to the events, is to be set the possibility of other events 

 having happened which are unrecorded or unreadable in the deposits 

 which we have been considering. 



Discussion. 



The Peesident anticipated a considerable amount of discussion 

 on a question which had already engaged the attention of so many 

 writers. 



Prof. Prestwich thought the sections of much interest, but 

 wanted to know the terras of the discussion. What was meant 

 by the so-called post-glacial deposits indicated in the column ? There 

 was no evidence of their being of post-glacial age, either in the 

 presence of extinct Mammalia or of boreal Mollusca. 



The Author explained that all the deposits between the Marine 

 Low-level Boulder-clay and the recent deposits were included in 

 his "post-glacial." 



Prof. Prestwich remarked that these deposits contain only recent 

 shells : they are in fact merely ordinary alluvial deposits with the 

 submerged forests, so common round many of our coasts. The dates 

 the Author proposed to assign to these neolithic deposits were founded 

 on estimates entirely his own. But little reliance was to be placed 

 on the thickness of beds accumulated at th-e mouth of a river. 



Mr. De Hance observed that his first paper before the Society 

 dealt with this area and subject. It was a satisfaction to him to 

 agree with Mr. Reade's descriptions, though their conclusions were 

 at variance. The Mersey was a case of a valley within a valley, a pre- 

 glacial valley filled in with glacial deposits, a post-glacial one fringed 

 with river-terraces. The case was somewhat different as regards 

 the Kibble, west of Preston. He pointed out the great thickness 

 of the drift in the Fylde,its base being below sea-level for many miles. 

 He described the position of the peat-bed and its vertical range, and 

 the amount of excavation effected in the valley since the period of 

 the Upper Boulder-clay, the several stages being marked by terraces, 



* ' Principles,' 10th ed. vol. i. p. 545. 

 Q.J.G.S. No. 174. X 



