345 
from alternate liquefaction and freezing, he conceives rust be wholly 
suspended in these regions. 
As the tertiary strata prove that a warm climate certainly pre- 
ceded the assumed glacial epoch in the northern hemisphere, and as 
a mild chmate has since prevailed, Mr. Lyell says, there are three 
distinct phases of action to be considered in studying the supposed 
glaciers of Scotland: Ist, the coming on of the epoch ; 2nd, its con- 
tinuance in full intensity; and 3rd, its gradual retreat. At the 
commencement of the first condition, only the higher mountains 
would send down glaciers to be melted in the plains below, as at pre- 
sent in Switzerland, and in Chili between the 40th and 50th degrees 
of latitude. The ice would therefore thus be constantly advancing and 
retreating, but progressively, century by century, gaining ground, 
in consequence of diminishing summer heat; and pushing its terminal 
meraines forward, it would fill up lakes and other inequalities, till 
it finally reached the sea. During the second condition, when the 
motion of the ice would be very small, there would be, Mr. Lyell 
states, vast accumulations of snow filling the plains and valleys to a 
great height, and leaving bare only the higher peaks and precipices 
of the mountains. From these points, he conceives the erratic 
blocks were detached and conveyed almost imperceptibly along the 
surface of the frozen snow to great distances. Lastly, at the break- 
ing up and gradual retreat of the glaciers during the third period, he 
is of opinion, the boulders were deposited in the various situations 
in which they are now found, and that moraines, or lateral and trans- 
verse mounds, were successively deposited, and lakes formed, by which 
stratified materials were accumulated in certain positions. 
The second part of Dr. Buckland’s Memoir on the Evidence of 
Glaciers in Scotland and the North of England, was then read. 
The first part of the Memoir concluded with an account of glacial 
phenomena in the neighbourhood of Edinburgh (see ani, p. 337) ; 
and the line of country more particularly described in this portion 
extends southward from Edinburgh by Berwick, Newcastle, the Che- 
viots, the lake districts of Cumberland and Westmoreland, Kendal 
and Laneaster, to Shap Fell. A large portion of the low lands be- 
tween Edinburgh and Haddington is composed of till or unstratified 
glacier-mud containing pebbles. In the valley of the North Tyne, 
about one mile east of Haddington, is a longitudinal moraine mid- 
way between, and parallel to, the river and the high road; and 
Dr. Buckland directs attention to the trap-rocks which commence a 
little further eastward, and are intersected by the Tyne for feur or 
five miles above Linton, as likely to present scored and striated sur- 
faces, where the valley is most contracted. Four miles west of 
Dunbar another long and lofty ridge of gravel stretches along the 
right bank of the river ; and for three miles to the south-east of Dun- 
bar extends a series of terracés or modified lateral moraines. In the 
high valleys at the east extremity of the Lammermuir hills, between 
Cockburn’s Path and Ayton, moraines dispersed in terraces are also 
visible at various heights on both sides of the river; and on the left 
' gaargin of the estuary of the Tweed, three miles north of Berwick, 
242 
