184i PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 6, 



his paper on the Pleistocene deposits of the Isle of Man, read in 

 February 1846. 



The author is aware of a difficulty in supposing so large a mass 

 of sand, gravel and boulders to have been deposited within so li- 

 mited an area by the deliquescence of a single iceberg, and he there- 

 fore submits the question with diffidence to those who have observed 

 the carrying power and contents of icebergs in the present time, 

 and the character of the deposits resulting from them. 



Yet of the agency of ice*, in some shape or other, in the formation 

 of this mass, he thinks the grooved boulders afford a fair evidence; 

 and it only becomes a question of the greater or less depth of sea 

 above this particular locality at the period of its deposit. 



Supposing this very point to have been only just within the action 

 of the tides, and to have been left dry at low water, we still have this 

 fact before us, that the sea during the pleistocene or boulder deposit 

 was at a higher relative level with the land than it is at present, by 

 at least sixty fathoms. 



It ought also to be borne in mind, as supporting this hypothesis, 

 that the fossils occurring in the boulder deposit of this island, both 

 in the north and south, belong (as Professor E. Forbes has shown f) 

 to the second and third regions of depth J. We must bear in mind 

 also that the occurrence of boulders of the South Barrule granite, 

 in the boulder formation of the south of the island, is an indication 

 of the existence at the surface of that granitic boss at this period ; 

 and there can be no doubt that the general contour of the island 

 was then the same as at present. We have also taken the supposi- 

 tion that this mass of gravel on the Calf of Man might be only just 

 within the action of the tide, but in reality it might be many fathoms 

 below the sea-level, and yet be sufficiently elevated to detain an ice- 

 berg in its course. The author's opinion, as before stated, formed 

 from the study of this along with other phaenomena connected with 

 the boulder clay deposit in different parts of the Isle of Man, is, that 

 the sea-bottom of the glacial period has in this neighbourhood been 

 elevated certainly not less than 400 feet. 



We are thus in a condition to interpret more readily the occur- 

 rence of the granite boulders of South Barrule in various parts of 

 the southern basin of the island, at points even east of south from 

 the boss where the granite is " in situ.'' With a sea-level 400 feet 

 higher than at the present time, reaching therefore to the base of 

 the granitic boss, and with an arctic or subarctic climate, blocks of 



* Some particular condition oi packed ice may perhaps better assist in explain- 

 ing the phsenomenon. 



t Memoirs of the Geological Survey of Great Britain, vol. i. p. 385. 



X In addition to the fossils from the pleistocene marine formation of the island 

 which were noted in the author's former paper, published in the ' Proceedings' in 

 August 1846, as named by Professor E. Forbes, from the author's cabinet, the fol- 

 lowing have since been added : — Nassa macula ; N. monensis, described by Mr. 

 Strickland in the 'Proceedings'; N. reticulata', Fusus Sabini; Mactra solida; 

 Pleurotoma turricula, a smooth species. No. 127 of Forbes's Memoir in the Geo- 

 logical Survey ; Astarte compressa, several varieties ; Natica clausa ; Tellina hal- 

 tica : Corbula nucleus. 



