188 Reports and Proceedings. 
formed on the surface of the glaciers; and gave his reasons for 
thinking that no mass of detritus intervened between the glacier-ice 
and its rocky bed, but that all the stones which found their way 
there were quickly ground into mud, grinding the bed at the same 
time, and that this mud was instantly carried off by the water which 
is found abundantly beneath the glaciers. Mr. Campbell admitted 
that there were very considerable difficulties in fully explaining the 
phenomena of the Boulder-clay; but suggested that, from the great 
coldness of the climate of Scotland in the Glacial Period, there 
would be but a small supply of water from the melting of the ice, and 
that in the flattish country, where the Boulder-clay is principally 
found, the ice-sheet would not be much crevassed, so that surface- 
water would not easily find its way beneath, and the detritus over 
considerable spaces might thus escape removal. The mass of mud, 
stones, &c., would then be powerfully compressed and very gradually 
moved forward by the friction of the ice above; while the stones, 
being rubbed together while embedded in a slightly yielding matrix, 
might acquire their characteristic half-worn and scratched appear- 
ance. ‘This view of the case would also account for the so-called 
‘striated pavements,’ which would naturally be formed at any level 
which was for a time the bed of the ice, but which might afterwards 
be covered up by a fresh mass of clay and stones. Mr. Campbell 
thought that one of the strongest objections to the Land-ice Theory 
was derived from the local nature of a large portion of the boulders ; 
though this was generally used as an argument on the other side. 
He said he could easily understand how stones in a mountainous 
country might fall on the surface of the ice, and after being carried 
to a great distance might become involved in the Boulder-clay ; but 
he did not see how ice, creeping over a flat country, which it com- 
pletely covered, could break up the rocks beneath in large masses, 
instead of wearing them away by gradual and constant attrition. In 
conclusion, Mr. Campbell stated that in his opinion the evidence in 
favour of the formation of the Boulder-clay by a sheet of land-ice 
predominated ; but he did not wish to express himself too confidently 
on this point, and hoped that observations might be made on the 
effects produced by close-packed heavy ice drifting in somewhat 
confined waters, which might possibly throw some light on this 
obscure and difficult question. : 
II. March 2nd.—E. A. Winch, Esq., in the chair. The Monthly 
Lecture was given by W. Kneppir, Esq.—On the Unity and Perma- 
nence of Species. ‘The Lecturer described the views both of those 
who consider species to be permanent, and limited by strong charac- 
ters, being types of vegetable and animal life which have survived 
the lapse of ages unaltered, presenting the same forms and organiza- 
tions as those of their progenitors; and, secondly, of those who do 
not believe in the fixity of species, but are of opinion that, in 
consequence of the modifying influence of external agents upon 
organized beings, and of the hybridizing or crossing of ancient species, 
they have been subjected to incessant variation, even in their most 
important characters, thus giving rise to new types, which are them- 
