332 Chronicles of Science. | April, 
to exist below the boulder-drift a terrain erratique, a deposit of sand 
and clay horizontally stratified, and possessing all the characters of a 
river deposit—the terrain du transport of Elie de Beaumont, or the 
alluvion ancienne of Necker, the diluvium of recent authors—in the 
gravels of which the constituent rocks of the pebbles are found to be 
derived from the Alps or the sub-Alpine hills, whilst the boulder- 
blocks themselves also present different characters, according to the 
nature of the different valleys through which they have been carried, 
and corresponding to the rocks in situ in such valleys and their tribu- 
taries. It is evident, as M. Studer remarks, that the presence of this 
ancient alluvium throws us again into all those difficulties from which 
we thought ourselves freed by the hypothesis of the former greater 
extent of the glaciers. The difficulty, he thinks, may perhaps be 
diminished by reducing as much as possible the mass of those gravels, 
the transport of which across the lakes, before the great extension 
of the glaciers took place, seems incontestable ; and that, as these hori- 
zontal beds of ancient alluvium repose upen the denuded or sliced-off 
edges of the inclined beds of molasse, the date of their formation is 
necessarily placed between the catastrophe which elevated the Tertiary 
_beds and the epoch of the great extension of the glaciers. After a 
careful analytical survey of the physical and geological aspects of the 
lake-country, M. Studer comes to the conclusion of the insufficiency of 
erosion in accounting for the origin of the valleys and lakes of the 
Alps; and he considers there is no alternative but to recognize with 
M. Escher an intimate connection between a great number of the 
Alpine valleys and the inclined positions of the beds of the mountains 
which separate them. These, then, are true orographic valleys, such 
as M. Desor has noticed in the Jura, and to the two kinds he has 
described, the synclinal and isoclinal, there ought to be added for the 
Alps another—the anticlinal valleys. The cluses, he further considers, 
are evidently fractures enlarged by erosion ; and he adds a fourth class 
of valleys —those of subsidence. If lava-currents, which often traverse 
loose sand, do not burrow into the soil in their progress, is his argument, 
how can glaciers which have less power than even such currents of 
water as our senses will not detect the motion of, and which even at this 
slow rate move over an under-plane of water and ground-adherent ice, 
effect such enormous erosion as is involved in these lake-basins? He 
looks, therefore, to subsidences as their chief cause. In this case the 
ancient alluvium at the bottom of the basins involves the supposition 
of the lapse of a considerable period of time between the disturbance 
and the filling up of the depths of the crevasse; and as a proof of the 
occurrence of such an interval, he refers to the great difference between 
the faunas and floras of the last or newest beds of the molasse, and the 
first or oldest of those of the alluvium, urging how great a length of 
time it would require to produce such differences of climatal conditions 
as to enable a fauna such as that of the Confederate States to supplant 
the present fauna of Europe—a difference which is not greater, how- 
ever, than that between the animals of the Molasse age and the ele- 
phants, oxen, and deer of the Diluvium. 
