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adjacent plains, to bear marks similar to those produced by glaciers, 
viz. rounded, striated and polished surfaces, accompanied by the 
accumulation of mounds of gravel and erratic blocks in the low 
countries subjacent to them. 
Mr. Lyell has read a paper on the evidences of the action of ice 
in Forfarshire, and has re-examined that county in order to satisfy 
himself whether the boulder formation of the district, which he had 
previously regarded as the effect of drift-ice on submerged land, might 
be explained by the agency of ice acting on land already elevated 
above the sea. This latter conclusion he is now inclined to adopt, | 
believing that it is favoured by the mounds of transported materials 
bearing the form of morains, and for the most part unstratified, 
which occur on the sides of almost every valley in the Grampians, and 
sometimes across the glens at right angles, and almost blocking them 
up. He finds this opinion further confirmed by the local distribution 
of rocky fragments, and the evidence of their descent from higher 
to lower levels; and, lastly, he thinks that the rarity of organic re- 
mains in the till or boulder clay lends support to the same view. 
He mentions several deep lakes in the Grampians in Forfarshire, on 
the lower sides of which enormous accumulations of mud, gravel 
and angular blocks are strewed, which are derived from precipices 
on their higher side ; these materials would have filled up the lakes, 
unless we suppose them to have been formerly occupied by ice. 
The effects of drift-ice in producing alternations of stratified and 
unstratified deposits, and in causing curvatures in strata of sand and 
gravel, while underlying beds remain horizontal and undisturbed, 
were treated of last year by Mr. Lyell in a paper on the mud-cliffs of 
Norfolk. But in Forfarshivre the till, or unstratified matter containing 
boulders and angular blocks, is found everywhere underlying the 
stratified sand and clay; had the whole deposit been accumulated 
-under water, we might have expected alternations ; Mr. Lyell there- 
fore conjectures that the older till may have been formed in great 
part when the glaciers were gradually advancing over the country, 
at the period of the first coming on of a colder climate, and that 
portions of the morains may have become subsequently stratified 
in temporary lakes, or during floods in those valleys where stratifi- 
cation is observable. 
Another feature in the distribution of the transported materials of 
Forfarshire and Perthshire is a continuous stream, from three to three 
and a half miles wide, of boulders and pebbles, traceable from near 
Dunkeld by Coupar and the south of Blairgowrie into Strathmore, and 
thence in a straight line through the lowest depression of the Sid- 
Jaw hills from Forfar to Lunan Bay, a distance of thirty-four miles. 
No great river follows this course, but it is marked everywhere 
by lakes or ponds, which afford shell-marl, swamps, and peat-mosses, 
commonly surrounded by ridges of detritus from fifty to seventy 
feet high, consisting in the lower part of till and boulders, and in the 
upper part of stratified beds of gravel, sand, loam, and clay, which 
in some instances are curved or contorted ; the form of the included 
spaces is sometimes oval, sometimes quadrangular. No organic re- 
