Superficial Detritus of the Alps. 261 
enormous masses of broken materials into the adjacent low 
countries of France. 
In conclusion, it is suggested, that the dispersion of the 
far-travelled alpine blocks is a very ancient phenomenon, in 
reference to the historic era, and must have been coeval with 
the spread of the northern or Scandinavian erratics, which 
it has been demonstrated was accompanied chiefly by floating 
ice, at a time when large portions of the Continent and of 
the British Isles were under the sea. Viewing it, therefore, 
as a subaqueous phenomenon, Sir Roderick is of opinion that 
the transport of the alpine blocks to the Jura falls strictly 
within the dominion of the geologist who treats of far bygone 
events, and cannot be exclusively reasoned upon by the me- 
teorologist, who invokes a long series of years of sunless and 
moist summers, to account for the production of gigantic gla- 
ciers upon land under present terrestrial conditions. This last 
hypothesis is, it is shewn, at variance even with the physical 
phenomena in and around the Alps, while it is in entire anta- 
gonism to the much grander and clearly-established distribu- 
tion of the erraties of thenorth during the glacial period. The 
effect in each case is commensurate with the cause. The Scan- 
dinavian chain, from whence the blocks of northern Europe 
radiated, is of many times larger area than the Alps; and 
hence its blocks have spread over a much greater space. 
All the chief difficulties of the problem vanish, when it is ad- 
mitted that enormous changes of the level of the land, in re- 
lation to the waters, have taken place since the distribution 
of large erratics—the great northern glacial continent havin g 
subsided, and the bottom of the sea further south having 
been elevated into dry land, whilst the Alps and Jura, for- 
merly at lower levels, have been considerably and irregu- 
larly raised.—(Quarterly Journal of the Geological Society, 
No. xxi., p. 65.) 
