SCIENTIFIC SUMMARY. 
105 
Action of Ice in forming Lake-basins. — On this interesting subject we have 
received an important reprinted essay, by Mr. Thomas Belt. The author believes 
firmly in the action of glaciers in forming lake-basins. Supposing, he says, the 
existence of a depression in the pathway of a glacier which has reached such 
a depth that the ice simply fills it, what would happen ? At the bottom and 
sides of the hollow, the ice would be slowly melted by the earth’s heat, increasing 
with the depth of the basin. As the ice at the lower end of the basin melted, 
the whole mass would be pushed along by the thrust of the moving glacier 
above it. Into the crevice at the upper end would pour the water coming down 
the bottom of the glacier from above the basin, which would pass underneath 
and be forced out at the lower end, carrying with it the mud produced by the 
crushing down of the ice as it melted at the bottom, and by the grinding 
along its floor as it melted at the lower end of the basin. The water coming 
from above would assist in melting the ice, especially in summer ; but its 
most important effect would be the scouring out of the bottom of the basin, 
so that an ever clean face of rock would be presented to the huge natural 
tool operating upon it. Such an action would, in some measure, resemble 
that of a hollow drill which has been prepared for boring holes in rock through 
which a current of water is forced to carry off the ground stone. Mr. Belt 
accounts for the difference in depth of the lake-basins of Switzerland and 
Nova Scotia by stating that in one case the ice-chisel operated on hard 
granites and in the other on soft, easily-worn materials. — Vide Transactions 
of the Nova Scotia Institute of Natural Science , vol. II., No. 3. 
New Relation of the Calcaire Grossier. — MM. Briart and Cornet have dis- 
covered that this deposit is to be found at Mons, below the “ Lower Lan- 
denian,” which is the lowest of the Belgian tertiaries and the one immediately 
overlying the chalk. It is equivalent, according to Mr. Prestwich, to the 
Thanet sands of the London basin. The characters of this new bed are very 
similar to those of the Calcaire Grossier proper of the Oise, and to its Belgian 
equivalent, the “ Systeme Bruxellien ” of Dumont. The fossils which it 
contains are those of the Calcaire Grossier, which, moreover, do not occur in 
the intervening Landenian series or in their French representatives. It would 
appear then, that a fauna had existed for a time, disappeared in the inter- 
mediate beds, and then reappeared. A similar occurrence has been pointed 
out by M. Barrande in Bohemia. His observations go to prove that there 
were during the Silurian epoch different contemporaneous faunas, and that 
one of these obtained a temporary existence in a locality where the ancient 
fauna afterwards prevailed. This is what M. Barrande calls a colony. — Vide 
Bull, de V Acad. Roy ale de Belgique , Nov. 4. 
Fossil Forest in Arran. — Mr. E. A. Wiinsch has recorded a very curious 
discovery made by him while studying the carboniferous strata of North- 
eastern Arran. The beds of coal close to the coast are interstratified with 
layers of volcanic ash, and passing up through both may be seen the trunks 
of trees : — “ Trunks of trees 18 to 24 inches in diameter and 2 to 3 feet in 
height, standing erect upon the thin seams of shale and coal on which they 
grew, and covered by layers of ash two or three feet in thickness, are found 
regularly dispersed over the area.” The ash overlying them, in which they 
are embedded, contains numerous branches from 4 inches in diameter down 
to the minutest dimensions, some of the impressions displaying an almost 
