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



in the present course of the river, the Boulder-clay has been scoured 

 out in places down to the bed-rock. That the Mersey Yalley was 

 filled with Boulder-clay, at least to the level of that in the pre- 

 glacial channel at Widnes, will not, I think, be disputed by any- 

 one who knows the locality. There can be little doubt that the 

 Bonlder-clay originally filled up the channel of the estuary between 

 Liverpool and Birkenhead. A remnant of it lying in a Pre-glacial 

 channel, the existence of which I ventured in 1872 to predict, was 

 bored through in 1884 by the Mersey Tunnel Works. 



That Wallasey Pool, now occupied by the Birkenhead Docks, was 

 formerly levelled up with Boulder-clay is equally evident. The 

 Boulder-clay also exists, or formerly existed, in a thickness sufficient 

 for brickmaking, at Edgehill, on the Lancashire side of the Mersey, 

 at a level of 200 feet above Ordnance datum. 



When we consider the proximity of this locality to the Mersey, and 

 the tendency of deposits to work down to and accumulate at lower 

 levels, together with the proved instance of levelling up at Widnes, 

 we can hardly refuse to believe that the Mersey Valley was formerly 

 filled with Boulder-clay. To be assured that such a levelling up 

 takes place in a sea-bottom, we have only to examine a chart of the 

 Irish Sea, which represents a slightly undulating floor or vast plain 

 having no irregularities of level even approximating to those of the 

 valley of the Mersey. That there exist in this sea-area, could we 

 bare it down to the bottom rock, river-valleys or considerable 

 irregularities of contour, is shown by the " ditch " opposite Wigton- 

 shire, where the tide, which here flows very fast, has scooped out a 

 channel from 400 feet to 600 feet deep. The evidences that the 

 Mersey Valley was once levelled up with Boulder-clay is further 

 confirmed by the boring at Halewood, about three quarters of a mile 

 from Hunts-Cross Railway Station, which penetrated 137 feet of 

 drift presumably lying in a former tributary of the Mersey, of which 

 there was no evidence on the surface. 



The same may be said of that at Hooton, Cheshire, which went 

 through 169 feet of drift, lying in a vaUey. A bore-hole at Ilches- 

 ter wharf, Birkenhead float, penetrated 166 feet of alluvium and 

 drift, and I have little doubt that these are only a few out of 

 many examples of the general levelling up that took place during the 

 submergence of the Glacial period. 



It is thus quite clear that an enormous mass of glacial deposits 

 has been swept out of the Mersey Valley. That this was mainly 

 done by subaerial agents, when the land was at a higher level than 

 at present, is proved by the numerous tributary streams which 

 branched into it and are now partially filled with Post-glacial 

 deposits. Everywhere below the Post-glacial deposits, to be pre- 

 sently described, the Glacial beds are deeply eroded and show 

 evidences of long subaerial waste. 



How much time can be reasonably put down for these changes 

 will be presently discussed. 



Post-glacial Beds. — In a few places on the Boulder-clay surface 

 are found remains of vegetation, and above them a series of estuarine 



