18 
ORIGIN OP THE EUROPEAN TERTIARY 
[Ch. II. 
set of strata overlap another, in such a manner that the 
geologist might be enabled to determine the difference of age 
by direct superposition. 
ORIGIN OF THE EUROPEAN TERTIARY STRATA AT 
SUCCESSIVE PERIODS. 
We shall now very briefly enumerate some of the principal 
steps which eventually led to a conviction of the necessity of 
referring the European tertiary formations to distinct periods, 
and the leading data by which such a chronological series may 
be established. 
London and Hampshire Basins. — Very soon after the inves- 
tigation, before alluded to, of the Parisian strata, those of 
Hampshire and of the basin of the Thames were examined in 
our own country. Mr. Webster found these English tertiary 
deposits to repose, like those in France, upon the chalk or 
newest rock of the secondary series. He identified a great 
variety of the shells occurring in the British and Parisian 
strata, and ascertained that, in the Isle of Wight, an alter- 
nation of marine and freshwater beds occurred, very analogous 
to that observed in the basin of the Seine*. But no two sets 
of strata could well be more dissimilar in mineral composition, 
and they were only recognized to belong to the same era, by 
aid of the specific identity of their organic remains. The dis- 
cordance, in other respects, was as complete as could well be 
imagined, for the principal marine formation in the one country 
consisted of blue clay, in the other of white limestone, and a 
variety of curious rocks in the neighbourhood of Paris, had 
no representatives whatever in the south of England. 
Stibapennine Beds. — The next important, discovery of ter- 
tiary strata was in Italy, where Brocchi traced them along the 
flanks of the Apennines, from one extremity of the peninsula 
to the other, usually forming a lower range of hills, called by 
him the Subapenninesf . These formations, it is true, had 
* Webster in Englefield's Isle of Wight and Geol. Trans., vol. ii. p. 161. 
f Conch. Foss. Subap., 1814. 
