Changes in the Area of the Irish Sea. 61 



on the coasts of the Isle of Man, England, Ireland, and Scot- 

 land, we have, extending down to the present high water-mark, 

 and of various breadths, a low beach containing organic re- 

 mains of the fauna now inhabiting our seas ; at any rate, I 

 am not aware of any extinct species being found in it as in the 

 pleistocene beds. 



The slope is generally gradual from the base of the pleisto- 

 cene inland cliff to the present sea-level, and on it are situated 

 the older parts of many of our sea-port towns. 



Instances will probably occur to many here. The question 

 is, does the present high water-mark really determine the ex- 

 tent of the elevation of the land since the formation of the 

 cliffs in the pleistocene beds % I believe not. The elevation 

 must at one time have been greater than it is at present ; and 

 it may have been to such an extent as a second time to lay dry 

 a large portion of the area of the Irish sea. Why so % 



We find on various parts of the coasts submerged forests. 

 The growth of these forests we have good reason for attribut- 

 ing to a period posterior to the boulder-clay and drift-gravel, 

 posterior to the formation of the inland cliffs in the pleisto- 

 cene series. That they must have been so in some instances 

 is certain ; for, in the south of the Isle of Man, at Strandhall 

 in Pooloash Bay, we find a submerged forest with the roots of 

 the trees running down into the boulder-clay ; the boulder- 

 clay itself resting upon limestone-beds, grooved and scratched 

 in direction N.E. and S.W. very nearly, and containing 

 scratched boulders. As the drift-gravel was formed from the 

 destruction of the boulder-clay, during the period of the re- 

 elevation of the island, this at present submerged forest must 

 also have grown after the formation of the drift-gravel ter- 

 races, and after the formation of the cliffs in it, and in the 

 boulder-clay. In other words, it must have grown upon an 

 area left dry by an elevation of the Irish Sea bottom, at an 

 epoch subsequent to that long stationary period during which 

 the sea eat back its way into that vast plain connecting the 

 present British Isles, on which the Megaceros and other ani- 

 mals, which are now here extinct, lived and roamed. 



The submergence of these forests points again to another 

 subsidence of this area to the extent indicated by the present 



