the relative Age of Tertiary Deposits. 533 
been brought forward to support a similar opinion regarding 
the upper division of the crag. 
A small series of shells which I had collected at Ramsholt 
were placed by Mr. Lyell in the hands of M. Deshayes, for the 
purpose of ascertaining his opinion with regard to the pro- 
portion of extinct species. The conclusion he came to was 
that the per centage of recent shells was the same as in the 
larger collection, which he had examined when preparing his 
tables on tertiary fossils, and which were probably obtained 
from the upper bed. 
It is in allusion to this circumstance that a correspondent 
observes, “If such be the fact, there is an end to the question 
between my opponent and myself.” 
Now, the questions which have been under discussion are the 
presence of corallines in the Ramsholt bed, and the diluvial na- 
ture of the red crag. To decide these disputed points by sim- 
ply ascertaining the per centage of extinct species in the shells 
of the coralline crag, can only have been effected by a course of 
induction as novel in its nature as the results which it evolves 
are important; nor shall I stand alone in anxiously anticipating 
further information upon the application of a principle, which 
in some instances may so materially assist the labours of the 
geologist while prosecuting the investigation of tertiary for- 
mations. 
I turn however from the consideration of this subject, which 
is almost devoid of interest from its not having assumed a 
form that entitles it to serious discussion, to enter upon an in- 
quiry far more comprehensive in its nature and requiring a 
more profound method of investigation ;—an inquiry replete 
with the highest interest, from the practical suggestions which 
it offers, and still more so in the field which it throws open 
for legitimate inductive speculation. 
I have on a previous occasion dwelt upon the features which 
separate the coralline crag from the tertiary strata with which 
itis connected. The novelty of its general aspect, lithological 
character, and organic remains when contrasted with the ad- 
jacent fossiliferous beds cannot be disputed. But the ques- 
tion may fairly be asked, what is the nature of these changes, 
and what are the conclusions to be drawn from them? 
Do they accord with those well-known phenomena which are 
supposed to register the lapse of ages; or may they not rather 
be attributed to certain alterations in physical condition, which. 
over a small area may materially affect the existing organiza- 
tion during a comparatively short ‘period ? 
I am aware that Mr. Lyell in the last edition of his Prin- 
ciples of Geology refers the red and the coralline crag to the 
