Ch. XI.] LOESS OF THE VALLEY OF THE RHINE. , 151 
during some one or other of the tertiary periods ; and it is 
probable, that even those districts which were land before the 
commencement of the tertiary epoch, may have shared in 
the subterranean convulsions by which the levels of adjoining 
countries have since been altered. During such subterranean 
movements new alluviums would be formed in great abun- 
dance, and those of more ancient date so modified as to retain 
scarcely any of their original distinguishing characters. 
LOCALITIES OF NEWER PLIOCENE ALLUVIUMS. 
Sicily. — Assuming, then, that almost all the European allu- 
viums are tertiary, we have next to inquire which of them 
belong to the newer Pliocene period. It is clear that when a 
district, like the Val di Noto, is composed of rocks of this age, 
all the alluvium upon the surface must necessarily belong 
either to the newer Pliocene or to the Recent epoch. If, there- 
fore, the elevation of the mountains of the Val di Noto was 
chiefly accomplished antecedently to the recent epoch, we must 
at once pronounce alluviums, in the position indicated at a, 
diagram No. 26 (p. 139), to belong to the newer Pliocene 
era. I am informed, that gravel so situated occurs at Gram- 
michele in Sicily, containing the bones of the mammoth. 
Loess of the Valley of the Rhine. — There is a remarkable 
alluvium filled with land-shells of recent species, which over- 
spreads a great part of the valley of the Rhine, between Basle 
and Cologne, which, as it contains no remains of man or his 
works, we may refer to the newer Pliocene era. This deposit 
is provincially termed ' Loess/ or, in Alsace, f Lehm,' and has 
been described by many geologists, whose observations we 
have lately had opportunities of verifying *. 
According to M. Leonhard the loess consists chiefly of argil- 
laceous matter combined with a sixth part of carbonate of lime 
and a sixth of quartzose and micaceous sand. It may be de- 
scribed as a pulverulent loam, of a dirty yellowish-grey colour, 
* Among these we may mention MM. Leonhai'd, Bronn, Boue, Voltz, Steinin- 
ger, Merian, Rozet, and Hibbert. 
