114 REPORT—1840. 
ice is continually expanded. The effects of the movement, produced by 
this expansion, upon the rocks beneath the ice, are very remarkable. 
The bases of the glaciers, and the sides of the valleys which contain 
them, are found to be polished and scratched by stones fixed in the lowest 
region of the moving ice. The fragments of the rocks that fall upon 
the glaciers are accumulated in longitudinal ridges on the sides of the 
ice, forming deposits of stony detritus, which are called lateral mo- 
raines. As these descend into lower valleys, they assume a central 
place on the moving ice, and are called medial moraines. As the 
glaciers are continually pressed forwards, and often in hot summers 
melted back at their lower extremity, it results that the polished sur- 
faces, occasioned by friction on the bottom and sides, are left un- 
covered, and that terminal moraines, or curvilinear ridges of gravel 
and boulders, remain upon the rocks formerly covered by the ice. 
Thus we can discover, by the polished surfaces and the moraines, the 
extent to which the glaciers have heretofore existed, which is much 
beyond the limits they now occupy in the Alpine valleys. It is stated 
to result from similar facts observed by Professor Agassiz, that enor- 
mous masses of ice have, at a former period, covered the great valley 
of Switzerland, together with the whole chain of the Jura, the sides of 
which, facing the Alps, are also polished, and interspersed with angular 
erratic rocks, disposed like boulders in the moraines ; but since the 
masses of ice were not confined between two sides of a valley, their 
movements were in some respects different, and the boulders were not 
deposited in continuous ridges, but dispersed singly over the Jura at 
different levels. Professor Agassiz proposes the hypothesis that at a 
certain epoch all the north of Europe, and also the north of Asia and 
America, were covered with a mass of ice, in which the elephants and 
other mammalia found in the frozen mud and gravel of the arctic re- 
gions, were imbedded at the time of their destruction. The author 
thinks that when this immense mass of ice began quickly to melt, the 
currents of water that resulted have transported and deposited the 
masses of irregularly rounded boulders and gravel that fill the bottoms 
of the valleys; innumerable boulders having at the same time been 
transported, together with mud and gravel, upon the masses of the 
glaciers then set afloat. Professor Agassiz announced that these facts 
are explained at length in the work which he has just published, 
Etudes sur les Glaciers de la Suisse, illustrated by many large and 
accurate plates, which were laid before the Geological Section. 
On the Geology and Mineralogy of Canada. 
By Capt. Bavperey, R.A. 
The object of the communication was to draw attention to the pro- 
priety of undertaking a geological and mineralogical survey of Canada. 
For this end the author pointed out the advantage of such surveys in 
general, and the especial use of undertaking the survey of Canada, 
whose mineral resources had received little development. Iron, lead 
and copper exist in different combinations, and probably or certainly, in 
