230 Eerieirs — Prof. Bonne// — Ice-Work, Present and Past. 



greater than those of Greenland, and every slope becomes an ice-field 

 moving outwards and downwards to the bed of the sea (p. G8). 



The Alaska glaciers furnish many interesting facts. At the end of 

 the great Malaspina glacier portions of the old submarine morainio 

 material (at least 4000 feet thick) have been faulted up along eight 

 to ten miles into hills at least 3000 feet high, within the recent 

 period. Part of the glacier is covered by moraine with forests. 

 The glacier itself is seen, in natural sections, to lie on unconsolidated 

 gravel and clay ; and the surface-waters, forming tunnels in the ice, 

 carry much coarse debris into the subglacial drainage, and help to 

 form ridges of gravel and sand not unlike " kames " and "eskers" 

 (p. 74). 



The relation of glaciers to "lake-basins" is then taken in hand 

 (pp. 79-94). An abrading, but not any appreciable excavating, 

 power is allowed to glaciers. Although the occurrence of lake-basins 

 frequently coincides with glaciated regions, yet many such lakes 

 occur where no glaciers have been, and none occur at some places 

 which glaciers have traversed; and "the direct, evidence generally 

 is adverse to the excavatory action of ice, except under very special 

 circumstances." Differential earth-movements are real causes for 

 such sunken basins. 



The origin of the "Parallel Roads of Glen Roy " coming within 

 the range of glacial possibilities, is here discussed (pp. 94-107), after 

 a brief description, with a careful exposition of views hitherto held 

 — chiefly those advanced by Jamieson and Prestwich. The 

 objections to a marine origin for these " roads " are regarded as 

 insuperable. It is difficult to account for a local glacier huge and 

 solid enough to dam up so large a sheet of fresh water as would be 

 required to form these marginal terraces, at the time when Glen Roy 

 itself and parts of neighbouring valleys were free from ice ; so the ■ 

 subject is left open for further elucidation. 



The origin of the isolated mounds of gravel and sand known as 

 "kames" and "eskers" is also found to be too difficult for 

 definite explanation, even by one so experienced in ice as the author. 

 He gives the views of several writers ; and, indicating the weak 

 points, he cautiously concludes that, possibby, if these ridges be the 

 leavings of ice-sheets, the hypothesis of subglacial rivers offers 

 fewest difficulties ; but more probably they may be relics of beds of 

 rivers of melting ice and snow in the later part of the Glacial Epoch. 

 " Drumlins " are also treated of; described by others as large longi- 

 tudinal mounds of clay and stones. They are probably of sub- 

 glacial origin (that is, under glaciers). 



Both the merely local and the more continuous evidences of ice- 

 action in Britain are succinctly noticed (pp. 120-192), including the 

 Boulder-clay, lower and upper, and the intermediate Glacial Sands 

 and Gravels, especially of Norfolk, Yorkshire, the Midlands, 

 Cheshire, and Moel Tryfaen — also of Suffolk, Essex, and Middlesex. 

 The distribution of boulders from four main centres of dispersion is 

 carefully detailed. The proofs of glaciation in Scotland and Ireland 

 are considered (pp. 192-205), like those in England and Wales, with 



