GEOLOGY OF THE DISTRICT. 23 



of this would be that the drainage would be obstructed, and 

 thus, that the ancient forest would gradually disappear. 

 There seems to be no evidence of the subsidence extending 

 beyond the boundary of the alluvial deposits. The peat- 

 beds, as already said, dip towards the sea, and in some places 

 are actually below the line of the rise of the spring tides, so 

 that a sinking or contraction of the underlying sands seems 

 to be the only cause to which the phenomenon can be 

 attributed. At a little distance inland, the peat-beds are 

 exposed upon the surface of the ground, and here the peat 

 is collected and dried for use as cottage fuel. 



Some light was thrown upon the character of the deeper 

 strata by an unsuccessful attempt made a few years ago to 

 obtain water in Birkdale by boring. At sixty-five yards 

 depth, beds of red and light coloured marls, with crystals of 

 sulphate of lime and white granular gypsum, were met with ; 

 at sixty-seven yards, similar beds, with greater quantities of 

 sulphate of lime and gypsum ; at sixty-nine yards, beds, 

 again similar, but without sulphate of lime and gypsum. All 

 the deposits contained common salt, which was very evident 

 on the application of the tongue. Similar red and variegated 

 marls, containing gypsum, have been met with in the upper 

 Permian beds of Lancashire, and in the keuper marls of the 

 trias in Cheshire, but in the latter alone has salt yet been 

 found. It is probable, therefore, that the Birkdale deposits 

 are triassic, and that the strata is not very likely to yield an 

 abundant supply of fresh water. 



There can be no doubt that the British Islands were subject, 

 in the primeval times, to the rigours of a Polar climate. 

 Great Britain was once only a scattered archipelago of 



