380 Reports and Proceedings — 



In this paper the author arranged the Glacial phenomena of Scot- 

 land under the following three heads : — 



1. The great early glaciation by land-ice (maximum effects of 

 glaciation) . 



2. The period of glacial marine beds containing remains of 

 Arctic Mollusca, when most of the country was covered by 

 the sea. 



3. The time of the late glaciers, the special subject of the 

 paper. 



After expressing himself in opposition to the hypothesis of a great 

 polar ice-cap, the author described this last period as one not of 

 mere local glaciers, but as characterized by a return of a great ice- 

 sheet over nearly the whole of Scotland and Ireland ; but he stated 

 that this ice-sheet was probably neither so thick, so extensive, nor 

 so enduring as that of the first period of glaciation, which cleared 

 away every thing in the shape of superficial deposits down to the 

 hard rock. He believed, however, that in the last period the moun- 

 tains of Scotland and Wales, as well as the Pennine range and the 

 rest of the north of England as far as Derby, were covered with 

 thick ice, which in most parts reached down to the sea, and that 

 extensive snow-beds prevailed over the rest of England. In the 

 summer months the melting of these would give rise to streams of 

 muddy water, and produce the superficial deposits of Brick-earth, 

 Warp, and Loess ; whilst, when the currents were stronger, perhaps 

 from the thaw being unusually rapid, deposits of gravel would be 

 formed. This second ice-sheet would gradually become less and 

 break up into valley-glaciers, which in their retreat would leave 

 kaims and eskers at low levels, and moraines in the mountain- 

 glens. During this time no new great submergence of the country 

 took place ; and the last great modifications of the surface were 

 subaerial, and not submarine, the work having been done by frost, 

 rain, and glaciers. 



Discussion. — Mr. Jeffreys considered that the author's remarks relating to the 

 beds containing arctic species of Mollusca were not quite correct. Pecten islandicus 

 has been found in the drift of Scotland, but not in the seas at present surrounding 

 that country. At depths of 30 or 40 fathoms many arctic shells in a semifossil 

 state have been dredged, although they do not now live in those v^^aters. Mya 

 truncaia, a species which lives in very shallow water, has been found in much 

 deeper water in a semifossil state. At Fort William there is a bed containing 

 arctic species of shells seven or eight feet above the level of the sea. Arctic shells 

 of deep-water species have occurred 200 feet above the sea. Different conditions 

 have existed at different parts of the same seas, altering the character of the 

 Mollusca. The raising of the sea-beds above the level proper to enable certain 

 Mollusca to flourish would cause them to become extinct. 



Dr. Carpenter mentioned that cold water may be thrown up into very small 

 depths under certain circumstances. Near Halifax, N. S., the surface-water is 

 tolerably warm, but at no great depth the temperature falls to 35° F. In this case 

 the rotation of the earth causes the cold water from the north to surge up on its 

 western coast. The North Sea is a shallow sea, with a shoal in the middle, and 

 having off the coast of Norway a deep channel, which conveys the cold arctic under- 

 current, hence the east side is 10° F. colder than the west side. Local peculiari- 

 ties of disturbance of temperature may thus occur within short distances. 



Prof. Ramsay remarked that the author was not dealing with wide ocean- 

 deposits, but with ice coming down to the sea from the land. He had described 



