392 Geoloyical Society. 
which the trees were discovered. He afterwards applies the phe- 
nomena which he believes these processes produced to the condition 
and position of the trees and the arrangement of the surrounding 
sedimentary matter. ‘The author then enters into the inquiries, Ist, 
the time which the trees may have required to attain their dimen- 
sions ; and consequently the minimum of years requisite for the accu- 
mulation of the vegetable matter; and, 2ndly, what thickness of 
vegetable matter was necessary to form the stratum of coal nine 
inches thick, over which the trees stand. Mr. Schomburgk is of 
opinion that a dicotyledonous tree which would require in temperate 
climates one hundred years to attain a certain diameter, would arrive 
at the same dimensions within the tropics in sixty or eighty years. 
The largest of the fossil trees forming the immediate subject of the 
paper is equal in circumference to an oak of 130 years growth in 
this climate, or about 100 for a climate equal in temperature to that 
of the tropics. Allowing therefore that some time elapsed after the 
commencement of vegetation on the surface of the then dry land 
before the trees began to grow, Mr. Bowman infers, that 100 years 
must be the minimum of time which would be required for the 
production of the vegetable matter out of which the nine inches of 
coal were produced. With respect to the depth of the stratum of 
vegetable matter from which it was formed, Mr. Bowman takes for 
his data, the thickness of the bed of coal, nine inches; the distance 
between the top of the seam and the bottom of the trunk under the 
arch formed by the roots, fifteen inches; and for the distance to the 
surface of the ground, four inches, or in all twenty-eight inches ; 
whereby he infers that the thickness of the solid coal is equal to about 
one-third that of the vegetable matter out of which it was produced. 
June 10.—A paper was read on the polished and striated surfaces 
of the rocks which form the beds of Glaciers in the Alps, by Pro- 
fessor Agassiz. 
This paper was accompanied by a series of plates intended to re- 
present the effect of glaciers upon the rocks over which they move. 
These effects, consisting of surfaces highly polished, and covered 
with fine scratches, either in straight lines or curvilinear, according 
to the direction of the movement of the glacier, are constantly found, 
not only at the lower extremity, where they are exposed by the 
melting of the glaciers, but also, wherever the subjacent rock is 
examined, by descending through deep crevices in the ice. Grains 
of quartz and other fragments of fallen rocks, which compose the 
moraines that accompany the glaciers, have afforded the material 
which, moved by the action of the ice, has produced the polish and 
scratches on the sides and bottom of the Alpine valleys through which 
the glaciers are continually, but slowly descending. It is impossible 
to attribute these effects to causes anterior to the formation of the 
glacier, as they are constantly present and parallel to the direction of 
the movement of the ice. ‘They cannot be considered as the effects 
of an avalanche, for they are often at right angles to the direction in 
which an avalanche would descend; they are constantly sharp and 
fresh beneath existing glaciers, but less distinct ou surfaces which 
