344 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



drained by a deep cutting towards the close of the seventeenth 

 century. I cannot help thinking, however, that these lakes, and their 

 resulting deposits of shell marl, were of recent date compared with 

 another alluvium which originally occupied the entire basin of the 

 Curragh from sea to sea, and was widely spread over the low grounds 

 of the southern basin of the island. 



The marl, which is used largely in the northern districts for agri- 

 cultural purposes, is of three kinds, a reddish-brown marl being 

 obtained in the parishes of Kirk Bride and Andreas, a bluish-brown 

 marl generally raised in Jurby parish, while a light-coloured shell 

 marl chiefly prevails in Ballaugh. The first evidently belongs to the 

 boulder clay formation, the second is perhaps the older alluvium, and 

 the third is the deposit of the lakes drained in the seventeenth century. 



It has been stated that the remains of the Irish Elk {Megaceros 

 hibernicus) have only been found in this last deposit, the shell marl ; 

 but I have myself discovered them in the blue marl of the south of 

 the island, which I believe to be identical with the blue marl of the 

 north or Jurby marl. The bog timber is generally procured from 

 the turf, which is in many places from ten to twelve feet thick. It 

 is stated in Sacheverell's ' History of the Isle of Man,' published 

 in 1702, that trees of very large dimensions had been found in the 

 Curragh, twenty feet below the surface, with their roots firm in the 

 ground and their trunks laid over in a north-easterly direction*. 

 Dr.Macculloch also mentions, and living witnesses have confirmed the 

 statement, that twenty years ago, after a violent storm, lasting three 

 days, the sands in Poolvash Bay being denuded in front of Mount 

 Gawne, trunks of trees were discovered lying prostrate towards the 

 north, as if overthrown by the force of waves coming in upon them 

 from the south. In the autumn of 1845 I discovered, about a mile 

 to the east of Mount Gawne, at the mouth of Strandhall brook, be- 

 twixt high and low water, a bed of turf one foot thick, and the 

 trunks of trees (oak, ash and fir), of which I counted eight in an 

 erect position, and traced the roots of one (an oak) several feet in 

 the stiif alluvial blue loam, which was evidently the subsoil upon 

 which the trees grewf. The alluvium (which is here not more than 

 three feet thick) rests in part upon the nearly horizontal limestone 

 and in part on a denuded bed of the boulder clay, and is situated 

 at the opening towards the sea of one of the valleys of denudation. 

 A few yards to the east and west of this submerged forest we have 

 a raised beach of a recent period. It is possible at this particular 

 spot to explain the phaenomenon by supposing the bank driven back 

 upon the land, and that formerly it intervened between this forest 

 and the sea, and by a partial damming up of the water of the stream 

 formed a swamp, and the alluvial deposit in which the turf and trees 

 grew. However this may be, it is certain that this same alluvial 



* Bishop Wilson, in his * History of the Isle of Man,' notices the remarkable 

 occurrence of a layer of peat for some miles together, under a layer of gravel, clay, 

 or earth, two or three, or even four feet thick. 



t It is singular that the trunk of an oak-tree which has been removed from the 

 submerged forest at Strandhall exhibits upon its surface the marks of a hatchet. 



