693 
of Edinburgh, Session 1877 - 78 . 
the previous Reports will yet allow the problem to be solved. 
But at all events it may be conceded that some new facts have been 
ascertained, which throw considerable light on the question. 
I venture to indicate what appear to me to be several con- 
clusions warranted, though in doing so I offer only my own 
opinion. Perhaps the Committee, after more information has 
been obtained, may be induced to consider whether they will pro- 
nounce on the various questions of interest which the subject 
presents. 
I confine myself this evening to only a few points, and chiefly 
to illustrate what occurs in our last Report. 
3. The boulders referred to in the Report may be divided into two 
classes. 
First, There are boulders which, from the nature of the rock com- 
posing them, are so soft and friable, that they could have been trans- 
ported only short distances — such as sandstone, coal, and shale. 
In the Report, examples are given of such boulders, from Berwick- 
shire and Mid- Lothian. 
The second class of boulders, namely, such as are ascertained 
to have come from remote quarters, are composed of rocks, hard, 
compact, and homogeneous in composition; such as basalt, green- 
stone, granite, felspar, quartz, greywacke, and old conglomerate. 
Boulders of these rocks have been found even as far as 80 or 100 
miles from the parent rocks; and, generally speaking, they are well 
rounded, presenting evidence of enormous friction undergone whilst in 
transitu; and even in some cases acquiring almost a spherical shape. 
Specimens of small sjiherical boulders are now on the Society’s 
table. 
There are, however, exceptions to the rule that boulders of hard 
compact rocks are generally well rounded. Cases of boulders of 
these hard rocks occur extremely angular in shape. Examples are 
shown in this Report, by the lithographs appended to it, and in 
previous Reports. These angular boulders are almost invariably at 
high levels, on the sides of mountains or near their tops. The well 
rounded boulders are generally at loiv levels, and most frequently 
imbedded in boulder clay. 
4. It will be asked, whether the Committee has in any case ascer- 
tained the parent rock from which a boulder has come. 
VOL. IX. 4 y 
