212 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan, 4, 



I classed under the heads of, — 1st. Boulder-clay, and erratic blocks ; 

 2nd. Diluvium ; 3rd. Drift-gravel ; and 4th. Alluvium. 



In a subsequent paper, read before this Society on January 6th, 



1847, on the Geology of the Calf of Man*, I stated that' I felt 

 inclined to remove to the division of Boulder-clay a large portion of 

 the accumulations which I had classed under the head of " dilu- 

 vium," confining this term to those masses of insular granite 

 and detritus which had been carried from their original position 

 to higher localities, and, as I then presumed, by violent diluvial or 

 cataclysmal action. I thought it impossible that any ordinary action 

 of icebergs could elevate to a height of upwards of 600 feet (and 

 that within a distance of a mile and a half from their parent source) 

 such immense quantities of granite and other rocks which I traced 

 to the very summits, and abundantly on the other side of our highest 

 southern mountains. In the same paper I stated my conviction that 

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

 depressed and raised again to an extent of not less than 4U0 feet, 



Mr. Darwin in his paper " On the Transportal of Erratic Boulders 

 from a lower to a higher level, read before this Societyf on April 1 9th, 



1848, in commenting on these facts, (which I had also more fully 

 detailed in my ' History of the Isle of Man,' published that same 

 year,) has shown how, by presuming a slow subsidence of the land, 

 through a lengthened period, the agency of ice could be effectual to 

 the producing these singular phsenomena without necessarily calling 

 in aid any violent cataclysm. 



A further and closer examination of the locality convinces me 

 of the soundness of Mr. Darwin's views, and that a gradual submer- 

 gence took place of the Isle of Man to an extent of not only 400, 

 but at least 1600 feet. 



I shall very briefly draw attention in this paper to some of the 

 evidences of the great probabilities of this hypothesis as presented to 

 us in the Isle of Man. 



I should premise, that I consider all the appearances of the true 

 boulder-clay {i.e. clay or loam imbedding scratched rocks and 

 boulders principally,^ as pointing to a sinking condition of the land ; 

 for, as proposed in my paper "On the Tertiaries of the Moray Firth J," 

 read April I8th, 1849, " the very circumstance, of the rocks in as 

 well as under the boulder-clay being grooved and polished, is in 

 itself a strong evidence of subsidence ; the grooving must have taken 

 place prior to the covering up of the fundamental rock ; and the 

 same must be true of each successive fragment in the superior mass." 



I consider, at any rate, this hypothesis as presenting as simple 

 a solution of the facts as the supposition of a mud-glacier sliding 

 forward over itself through several miles of country and over every 

 irregularity of ground. 



I would observe that there was a period, prior to the subsidence 

 and emergence of which I am about to speak, when the Isle of Man 



* Quart. Journ, Geol, Soc. vol. iii. p. 1 79 ; with sections, 

 t Quart. Journ. Geol. Soc. vol. iv. p. 315. 

 X Quart. Journ. Geol. Soc. vol. vi. p. 10. 



