of Edinburgh, Session 1881-82. 
789 
On a minute inspection of erratic blocks, certain features were 
noticed which seemed to indicate the forces to which they had been 
subjected. Thus on many of them, deep scratches, ruts, and groov- 
ings were found, as if sharp pebbles or stones harder than themselves, 
had been squeezed against them under great pressure. It was also 
observed that, when a block had a long and a short axis, the longer 
axis was generally parallel with any well marked scratches or striae 
on its surface; and, moreover, that the direction of these striae 
frequently coincided with the direction of the parent rock. 
These circumstances soon led geologists to speculate on the nature 
of the agencies which could have effected a transport. 
After alluding to the different theories which had been suggested, 
to account for boulder transport, the paper proceeds as follows : — 
It is not my intention to discuss these theories, or say which appears 
the most probable. I allude to them merely to indicate the 
tremendous character of the agencies, which it is found necessary to 
invoke for the solution of the problem, — agencies all implying a very 
different condition of things in Scotland, as regards configuration of 
surface and climate, from what now prevails. These phenomena are 
the more interesting, because, as most of the erratic blocks lie above 
all the rocks, and very frequently even above the beds of clay, gravel, 
and sand, which constitute the surface of the land we inhabit, they 
indicate probably the very last geological changes which occurred in 
this part of the earth’s surface, and which there are some grounds for 
supposing, may even have occurred since this country was inhabited 
by man. 
The basis on which geologists have been obliged to build their 
theories, it must be admitted, is sufficiently narrow. It consists 
merely of observations made casually by individuals, who have 
noticed certain appearances in districts which they happen to have 
visited ; and, therefore, it is little to be wondered at, that more than 
half a century has been required for procuring the information, scanty 
as it is, which has been obtained. 
What appears desirable for expediting the solution of the problem, 
is to discover and organise a staff of observers, for the purpose of 
discovering facts likely to throw light on the subject, and of making 
these facts known from time to time, both with a view to verification, 
and as a basis for further speculation. 
