112 T. M. Beade— Post- Glacial Geohgtj of 



vaUey deposits, described by Binney, Trimmer, and others, the great 

 mass of Post-Glacial deposits of Lancashire and Cheshire lie on the 

 margin of the sea-coasts, and of the rivers Mersey, Dee, and Eibble, 

 and follow with remarkable regularity the 25-ft. contour line below 

 which the bulk of them lie. 



The Lancashire deposits between Waterloo and the river Douglas 

 have a coast-line of about 24 miles long, are 4 miles wide at Formby, 

 measuring from high- water mark, and run inland in the valleys of 

 the rivers Alt and Douglas about 8 miles respectively. They also 

 extend into the valley, in which was formerly Martin Mere, about 7 

 miles, joining the Douglas valley deposits at Kufford, through a 

 narrow neck. Between Martin Mere and the river Douglas the 

 Boulder-clay rises through the Post-Glacial deposits to a maximum 

 height of 58 feet above Ordnance datum, and occupies an area of 

 about 8|^ square miles. The total area of the Post-Grlacial deposits 

 lying inland, from high-water mark at the coast-line, forming what 

 I call the Formby plain, is about 75 square miles. Nearly the whole 

 of this plain, though much of it lies below high water, is, through 

 the drainage works of the Alt and those at Crossens, now under 

 cultivation. In Cheshire the equivalents of these deposits form 

 another plain drained by the Birket, a brook falling into Wallasey 

 Pool, the lowest and major part of which pool is now occupied by 

 the Birkenhead Docks. This plain is about 6 miles long at the coast, 

 and has an area, inland of high- water mark, of about 1\ square 

 miles. 



In addition to the Formby and Birket plains, there are numerous 

 equivalent formations, such as the Ince. and Helsby Marshes in 

 Cheshire, and alluvial or tidal flats fringing the Mersey, and reach- 

 ing above Warrington ; with similar formations on the Dee and 

 Eibble, occupying together many square miles. 



Base of the Deposits. — The base upon which the deposits rest is 

 nearly everywhere Boulder-clay, under which occur the sandstones 

 and marls of the Trias. A careful comparison of borings and sink- 

 ings at various points has convinced me that at the base of the 

 deposits, and forming the surface upon which they rest, is a Post- 

 Glacial beach cut in the Boulder-clay, and that the valleys of the 

 Alt, the Douglas, and the Eimrose brook pass under the deposits 

 seaward, to a considerable depth below low-water mark ; the whole 

 being filled and levelled up with the marine formations and old land- 

 surfaces now under consideration. Borings taken on the Waterloo 

 shore show the clay from 6 to 9 feet below the surface, and other 

 borings show a gradual deepening of the Post-Glacial strata north- 

 wards, until at Birkdale it reaches 80 feet ; the depth of the strata 

 bearing a pretty constant proportion to the recession inland of the 

 25-feet contour line. A well-sinking at Seaforth Station showed 40 

 feet of peat and 10 feet of silicious silt, without reaching the Boulder- 

 clay or the rock, showing that the Eimrose brook formerly, when the 

 land was elevated, flowed down a deep and narrow galley, now 

 levelled up. Again, at Eufiford, piles were driven 70 feet into the 

 silts without bottoming them, proving that the Douglas, at the same 



