300 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 1, 



westward by an equally, if not much more, extensive tract of Silurian 

 rocks, the limits of which as yet we have been unable to ascertain. 

 The chief, indeed, it may be said, the only navigable channel through 

 which this Silurian district has yet been reached is Lancaster Sound ; 

 it is probable, however, we may find it continuous to the westward 

 with the American series of the same rocks. Through the labours 

 of Prof, Jameson and M. Konig, thirty years ago*, and of Mr. Salter 

 only very recently f, some of the numerous Silurian fossils peculiar 

 to North Somerset, North Devon, and the North Georgian Islands, 

 have been described from the fragmentary specimens brought home 

 by the ships engaged in the discovery of these places during the last 

 thirty years %. 



Drift Deposits. — On Cornwallis and Beechey Islands in Barrow 

 Straits, west of Lancaster Sound, deposits containing existing arctic 

 sea-shells, occur at every elevation up to nearly 1000 feet, — the 

 greatest height attained by any part of that district. On the undula- 

 ting slopes and along the raised beaches of this Silurian district of the 

 North Georgian Islands, &c., occur travelled materials, such as frag- 

 ments of anthracite, greenstone, quartz, serpentine, gneiss, and 

 granite, but all of such small size, that their mode of conveyance to 

 their present position is clearly referable to the action of coast-ice 

 (previous to the elevation of the land), such as at the present day 

 occupies the comparatively shallow seas in the inlets and channels of 

 that district. 



On the Greenland side of Davis' Strait, on the contrary, we find 

 immense travelled boulders of gneiss and granite resting on the 

 islands and the coast, which have been brought there at former 

 periods by floating icebergs, previous to the elevation of the coast 

 above the sea-line. The probable causes of these difi'erences of ice- 

 action on these two opposite coasts are explained in the subsequent 

 observations. 



It may be noticed also, that, from the observations of Dr. Pingol 

 and Capt. Graah, the west coast of Greenland presents evidence of 

 its now undergoing the process of gradual submersion. 



Glacial contentions. — At Cape Farewell the fiords run so far into 

 the interior, that none of the icebergs escaping into them from the 

 great inland glacier ever reach Davis' Straits, and if the navigator 

 meets with icebergs in the neighbourhood of this promontory, they 

 must have drifted to it from other sources. As we advance north- 

 ward along the coast of West Greenland, and thus diminish the 

 annual mean temperature both of the sea and of the atmosphere, we 

 find the glacier approaches nearer and nearer the coast-line, until in 

 Melville Bay, lat, 75°, it presents to the sea one continuous wall of 

 ice, unbroken by land, for a space of probably seventy or eighty miles. 



* Appendix to Capt. Penny's Voyages. 



t Appendix to Sutherland's Journal of Capt. Penny's Voyage, 1852, 2 vols. 8vo. 

 See also Mr. Salter's Paper, infra, p. 312. 



J The Rev. Mr. Longmuir, of Aberdeen, found numerous specimens of the 

 genus Rhynconella in the ballast of the " Prince Albert," a ship recently returned 

 from Batty Bay, Prince Regent's Inlet, on the eastern shore of North Somerset. 



