92 Sir Charles Lyell [April 27, 



blocks of mica-schist, from 30 to 50 feet in their longest diameter, 

 on the south-east side of the Lenox range C ; whereas no similar 

 fragments of mica-schist, whether large or small, are found in any 

 part of the Richmond valley, or on the ridge B, or indeed anywhere 

 between A and the Hudson river. 



Some boulders of white quartz rock, two or three feet in diameter, 

 make a part of almost every train, as well as of the subjacent drift, 

 and these may be traced to hills, between the Canaan ridge and the 

 Hudson river, where the Potsdam sandstone has been altered into 

 quartzite. 



Sir Charles then proceeded to explain his theory. He believes 

 that all the large erratics have been transported to the places they 

 now occupy by floating ice, — not by icebergs, nor by terrestrial 

 glaciers, but by coast-ice. The hypothesis of glaciers is out of the 

 question ; because, even if we could imagine that in lat. 42° 30' N., 

 the ridges ABC, now only from 1000 to 2000 feet above the sea, 

 once rose, and that at a period, geologically speaking, very modern, 

 to such an elevation as to enable them to generate glaciers, still 

 such glaciers could not have descended from the higher regions in 

 one direction only. They would have radiated from a centre, 

 carrying as many blocks westward as eastward. Their course, 

 moreover, would have been principally S.S.W., or down the valleys 

 now separating the ridges, instead of being south-east, or almost at 

 right angles to the valleys. If, on the other hand, we assume that 

 the country was lower instead of higher, so as to have been sub- 

 merged beneath the waters of a sea, in which icebergs floated 

 annually from arctic regions, these bergs might bring with them 

 gravel and stones of northern origin, but could not without the aid 

 of coast-ice become freighted with blocks derived from the very 

 region referred to in this discourse, (lat. 42" N.) The northern ice 

 might aid, by chilling the waters of the ocean, and increasing the 

 quantity of coast-ice in a low latitude, but it could do little more. 



N.W. 

 Canaan. 

 A 



Sea 



d, e Masses of floating ice carrying fragments of rock. 



Suppose the highest peaks of the ridges ABC, in the annexed dia- 

 gram, to be alone above water, forming islands, and d e to he masses 

 of floating ice which drifted across the Canaan and Richmond 

 valleys, at a time when they were marine channels, separating islands, 

 or rather chains of islands, having a N.N.E. and S.S.W. direction. 

 A fragment of ice, such as d, freighted with a block from A, might 

 run aground, and add to the heap of erratics at the N.W. base of 

 the island B, or passing through a sound between B and the next 



