no 
ISLAND LIFE. 
[part I. 
found underneath moraines, drift, and other late glacial deposits, 
but never overlies them (except in special cases to be hereafter 
referred to), so that it is certainly an earlier deposit. 
Throughout Scotland, where “till ” is found, the glacial striae, 
perched blocks, roches moutonnees, and other marks of glacial 
action, occur very high up the mountains to at least 3,000 and 
often even to 3,500 feet above the sea, while all lower hills and 
mountains are rounded and grooved on their very summits ; 
and these grooves always radiate outwards from the highest 
peaks and ridges towards the valleys or the sea. 
Inferences from the Glacial Phenomena of Scotland. — ISTow all 
these phenomena taken together render it certain that the 
whole of Scotland was once buried in a vast sea of ice, out of 
which only the highest mountains raised their summits. There 
is absolutely no escape from this conclusion ; for the facts which 
lead to it are not local — found only in one spot or one valley — but 
general throughout the entire length and breadth of Scotland ; 
and are besides supported by such a mass of detailed corrobo- 
rative evidence as to amount to absolute demonstration. The 
weight of this vast ice-sheet, at least three thousand feet in 
maximum thickness, and continually moving seaward with a 
slow grinding motion like that of all existing glaciers, must have 
ground down the whole surface of the country, especially all the 
prominences, leaving the rounded rocks as well as the grooves 
and striae we still see marking the direction of its motion. All 
the loose stones and rock-masses which lay on the surface would be 
pressed into the ice ; the harder blocks would serve as scratching 
and grinding tools, and would thus themselves become rounded, 
scratched, and striated as we see them, while all the softer masses 
would be ground up into impalpable mud along with the 
material planed off the rocky projections of the country, leaving 
them in the condition of roches moutonnees. 
The peculiar characters of the “till,” its fineness and tena- 
city, correspond closely with the fine matter which now issues 
from under all glaciers, making the streams milky white, 
yellow, or brown, according to the nature of the rock. The 
sediment from such water is a fine unctuous sticky deposit, 
only needing pressure to form it into a tenacious clay ; and 
