520 Geological Society. 



of Scotland might present an island " almost wholly covered with 

 everlasting snow," having each bay terminated by ice-cliffs, from 

 which great masses yearly detached would transport fragments of 

 rocks to distant regions ; and infers, that as in other parts of the 

 world there are conditions in which ice becomes a motive power, 

 such conditions may also have existed in our latitudes. 



Mr. Murchison has also proposed to explain the dispersion of 

 erratic blocks now resting on beds of clay and sand containing recent 

 species of arctic shells over large districts in the interior of Russia, 

 by supposing " that they had been floated in icebergs, which break- 

 ing loose from ancient glaciers in Lapland and the adjacent tracts, 

 were drifted southwards into seas which have been since laid dry." 

 He further suggests, that icebergs loaded with detritus may, by grating 

 upon the bottom of these seas, have produced the parallel striae and 

 polished surfaces on the rocks over which they were drifted ; and con- 

 cludes with admitting so much of the glacial theory as to allow that 

 in former days glaciers probably advanced further to the south, and 

 occupied many insulated tracts, and to a much greater extent than 

 at the present day. 



We learn from Professor Hitchcock's excellent work on Element- 

 ary Geology (August 1st, 1840), that parallel striae and furrows, 

 accompanied by rounded and polished surfaces of all the harder 

 rocks, and that vast longitudinal mounds and tumuli of detritus, and 

 erratic blocks sometimes at the distance of many hundred miles from 

 their native place, have been lately observed in so many provinces of 

 the United States, that these phaenomena may be placed in the category 

 of geological constants in North America. They have been noticed 

 in Maine, New York, New England, Rhode Island, Massachusetts, 

 Connecticut, Ohio, Michigan, and Illinois, at various elevations, 

 sometimes from 3000 to 4000 feet above the level of the sea ; the 

 prevailing direction of these striae and furrows is from N.W.to S.E. 



We have also long been familiar with the streams of erratic blocks 

 that have been traced south and south-eastwards from the moun- 

 tains of Scandinavia to the shores of Germany ; and more recently 

 Sefstrom and Botlingk have informed us that polished striated and 

 furrowed surfaces are also of constant occurrence in Norway, Sweden, 

 Finland, and Lapland, their mean direction being, like the course of 

 the erratic blocks, from N.W. to S.E. Botlingk, however, has ob- 

 served that some of these furrows have centres of dispersion (as in 

 the case of those produced by modern glaciers that radiate from the 

 Alps), and follow the direction of the major axis of each valley, 

 whilst the general direction of the striae on the summits in Scandina- 

 via is from N.W. to S.E. He, moreover, states, that in the south of 

 Sweden the striae incline southwards, but on the east of Lapland 

 northwards to the icy ocean ; the same conformity in the direction of 

 the striae with that of the major axis of each valley, occurs also in 

 Scotland, Cumberland and North Wales. 



Thus we find, that not only the highest and northern mountain 

 groups in the British Islands, but vast regions also of the continents 

 of Northern Europe and of North America have been subjected 



