151 
of Edinburgh, Session 1878-79. 
question is, What was this agent? Was it a sheet of ice from Ross- 
shire, crossing the deep channels of the Great and Little Minch and 
flowing from the S.E. with a breadth of 120 miles? Or was it an 
ice-loaded oceanic current from the N.W. when the sea was, say, 
2000 feet above its present level ? 
As reference has been made to the low-lying level plains occurring 
in the Lewis, and to the beds of sea-shells in the till, it may not he 
deemed irrelevant to mention that there are on many parts horizontal 
terraces, hounded by cliffs which seem to indicate old sea-margins. 
Along the east coast, from Loch Seaforth to Stornoway, there are 
cliffs at heights of 11, 40, 81, 180, and 220 feet above the sea. The 
road from Stornoway to Garry-na-hine, for some miles, passes through 
a valley exhibiting a sea cliff at a height of from 210 to 220 feet. 
The valley through which the River Barvas flows to the sea, exhibits 
distinctly two terraces with cliffs, one 40 feet and the other 170 feet, 
above the sea. 
The theory of an ice-sheet from Ross-shire overspreading all the 
Outer Hebrides is too large a question to he discussed in this Report. 
But as having an important hearing on the question, the Convener 
may advert to the way in which the boulders are distributed in 
these islands. It has been already remarked that boulders are 
scanty on the east coasts of those islands, and in particular on the 
low-lying districts in the north of Lewis. It may he supposed that 
it is only natural that the boulders should he most abundant on the 
west coasts, as the highest hills are there. But it does not follow 
that the boulders, because they rest on these hills, were generated 
there. For example, the large boulder on the west flank of Dun-Ii 
in Iona, the numberless boulders on the sea cliffs on the west coasts 
of Tiree, Coll, Barra, Uist, Harris, and the Lewis, must have come 
from the westward, and been stranded on the first islands,- or 
submarine rocks or shoals, which impeded the farther progress of 
the ice which brought them. On that theory, it would not be 
difficult to explain why the boulders, whilst abundant on the 
mountains which fringe the west coast of the Hebrides, should he 
generally absent from the eastern and northern portions of the 
Lewis, where there are no hills, or any other obstruction to the ice 
in a sea, if one prevailed, about 1000 feet above the present level. 
If glaciers ever existed among the hills of Harris, their effects 
