MR. T. M. READE AN ESTIMATE OF POST-GLACIAL TIME. 203 



deposits containing marine shells, such as Tellina, Myiilus, Turritella, 

 &c., and in certain laminated clays Scrohicularia 2^'ip^^ciici in the 

 vertical position in which it lived. These Post-glacial deposits, where 

 they occur, have levelled up the inequalities produced by the pre- 

 vious subaerial erosion of the Boulder-clay, and they cover an exten- 

 sive area amounting to some 75 square miles between the Kibble 

 and the Mersey. It is difficult to say what their maximum thick- 

 ness is, but they are known to be, in places, 50 feet deep. The 

 deposits thin out landwards towards the ancient shore-line, so that 

 the borings in the centre of the Moss-lands show less than this 

 thickness *. 



None of these deposits, which are very general and are found 

 even as high up the river as Warrington, reach above the level of 

 the 25 feet Ordnance contour. It is manifest that they represent a 

 period of subsidence probably long continued. Mammalian remains 

 are found in these beds, but no extinct animal is represented. 



Lying upon these silts and blue laminated clays is a very exten- 

 sive peat-bed containing the stools of trees with the roots ramifying 

 into the clays or silts below. They are mostly oak, birch, and pine. 



That these trees have grown in the position in which they are 

 now found we have ample evidence. It therefore follows that the 

 Post-glacial estuarine beds in which they are rooted, after being 

 laid down, were elevated sufficiently for the efficient drainage of the 

 land, and there is strong reason to believe that at this time Great 

 Britain was united to the continent of Europe. Similar submarine 

 forests can be traced all round Great Britain and Ireland, the Isle 

 of Man, and the north coast of France, and I believe that most of 

 them are synchronous with our Lancashire and Cheshire submarine 

 forests. These forests represent, then, a period of general elevation 

 extensive in area, but of unknown vertical range. 



Since the growth of these extensive forests, there has again been 

 a subsidence, so that many of them became submerged beneath the 

 sea, and it is to this cause that we owe their partial preservation. 

 Along the littoral margin they are frequently found beneath blown 

 sand, and have, in places, recent estuarine silts deposited upon them. 



That all these changes occurred, there is evidence amply sufficient 

 to satisfy any unprejudiced mind. I know of few events in geology 

 more clearly recorded than those just detailed f. 



The channel of the Mersey, as proved by borings made during 

 the opposition to the Manchester Canal, is largely filled with Post- 

 glacial gravels. The precise age of these it is difficult to determine, 

 but probably they are the remnants of the Boulder-clay washed out 

 during the subaerial excavation of the present channel. Some of 



* See " Borings on the Southport and Cheshire Lines Extension Hallway," 

 Proe. of Liverpool Geol. Soc. 1884-5, p. 93. 



t See " Post-glacial Geology of Lancashire and Cheshire," Proc. of Liverpool 

 Geol. Soc. 1871-2; "The buried valley of the Mersey," ibid, 1872-3; "On a 

 section at Hightown," ibid. 1881-2 ; " The Mersey Tunnel, its Geological 

 Aspects and Eesults," ibid. 1884-5 ; " Some further Notes on the submarine forest 

 at the Alt Mouth," ibid. 1877-8 ; " A pi'oblem for Irish geologists in Post-glacial 

 Geology," Scientific Proceedings of the Eoyal Dublin Society, 1879. 



