256 Sir R. I. Murchison on the Distribution of the 
On the Distribution of the Superficial Detritus of the Alps, as 
compared with that of Northern Europe. By Sir RoDERICK 
IMPEY Murcuison, F.R.S., &e. &e. 
Referring to his previous memoir upon the structure of 
the Alps, and the changes which those mountains underwent, 
the author calls attention to the fact, that as during the for- 
mation of the molasse and nagelflue a warmer climate pre- 
vailed, so after the upheaval of those rocks, an entire change 
took place, as proved by the uplifted edges of such tertiary 
accumulations being surmounted by vast masses of horizon- 
tally-stratified alluvia, the forms of whose materials testify 
that they were deposited under water. The warm period, 
in short, had passed away, and the pine had replaced the 
palm upon the adjacent lands, before a glacier was formed in 
the Alps, or a single erratic block was translated. 
Though awarding great praise to the labours of Venetz, 
Charpentier, and Agassiz, which have shed much light on 
glaciers, and particularly to the work of Professor J. D. 
Forbes, in clearly expounding the laws which regulate their 
movement, Sir Roderick conceives, that the physical pheno- 
mena of the Alps and Jura compel the geologist to restrict 
the former extension of the Alpine glaciers within infinitely 
less bounds than have been assigned to them by those authors. 
True old glacier moraines may, he thinks, be always dis- 
tinguished, on the one hand, from the ancient alluvia, and, 
on the other, from tumultuous accumulations of gravel, boul- 
ders, and far-transported erratic blocks, as well as from all 
other subsequent detritus resulting from various causes 
which have affected the surface. He first shews, from the 
remnants of the old water-worn alluvia which rise to con- 
siderable heights on the sides of the valley, that in the 
earliest period of the formation of the Alpine glaciers, wa- 
ter, whether salt, brackish, or fresh, entered far into the re- 
cesses of these mountains, which were then at a considerably 
lower level, z.e., not less, perhaps, than 2500 or 3000 font 
below their present altitude. 
He next appeals to the existing evidences in the range of 
