TS, - 
mains have been found in the surrounding ridges, but they resemble 
greatly in form the mounds of detritus which may once have con- 
stituted the lateral, transverse, or medial morains of a great glacier. 
-Mr. Lyell compares the chain of this part of the Grampians to 
the Alps, the parallel chain of the Sidlaw hills to the Jura, and 
Strathmore to the great valley of Switzerland ; and the resemblance, 
he says, is increased by the occurrence in Strathmore and on the 
Sidlaw hills of blocks derived from the Grampians. He is of opinion 
that the agency of ice moving upon dry land may account for many 
appearances which are inexplicable on any other hypothesis, and that 
this theory must not be rejected because it fails to remove at once 
every obscurity ; especially as various other geological causes, such 
as oscillations of level in the land, the temporary submergence of 
portions of it during the supposed glacial period, and the action of 
drift-ice, may all have co-operated with glaciers to produce the boul- 
der formation. He also hints, that the glaciers of Switzerland, being 
situated eleven degrees further to the south, can present but an im- 
perfect analogy to the state of things which may once have prevailed 
in Northern Europe; it is to Sandwich or Kerguelen’s Land, or to 
South Georgia, and other regions of the southern hemisphere cor- 
responding in latitude to Scotland and England, that we must look 
for instruction; for these southern and antarctic lands are buried 
summer and winter beneath perpetual snow, which reaches even to 
the sea-coast, and yet in the case of South Georgia this perpetual 
snow is distant only nine hundred miles from Terra del Fuego, a 
country placed in the same latitude and yet clothed with luxuriant 
forests. Assuming therefore that the Grampians, Alps, and Jura, and 
all Seandinavia, were once permanently overspread with snow, he 
thinks we cannot therefore conclude that the whole globe between 
the fortieth parallel and the poles was invested simultaneously with 
a sheet of ice, nor even that the general climate of the whole earth 
differed materially from that prevailing in our own time. 
Mr. Murchison, in an admirable chapter (c.39.) of his Silurian Sy- 
stem, on the Position and Mode of Transport of Boulders which oceur 
in the Northern Drift, has stated good reasons for believing that such 
a change of climate may have taken place at the epoch of the trans- 
port of erratic blocks as permitted the formation of icebergs on the 
shores and rivers of Cumberland, Scotland, and Ireland; which be- 
ing drifted southwards, strewed their load of large stones and gravel 
over the bottoms of then adjacent seas. He also quotes with appro- 
bation the ingenious imagination by Mr. C. Darwin, of a proportional 
distribution of the land and water in central and northern Europe, 
very different from the present, and under which the southern part 
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 
