294 Prof. Necker on the History and Progress of Geology. 
thodical collection that exists in geognosy, and should be pro- 
foundly studied by those who engage in the pursuit of that 
science. In it, we find the types of Werner rather extended 
than altered. He demonstrates how the simplicity of these types 
is often disguised by the periodical alternation of two neighbour- 
ing formations, toward their mutual limits ; how a system of 
strata is "often rendered scarcely recognisable by the develop- 
ment of one of its strata, in particular, at the expence of the 
others ; and, lastly, how certain products reappear, as by oscilla- 
tion, at certain different epochs of the series. 
Considering the science in this manner under a very elevated 
and very general point of view, he succeeded in explaining many 
discrepancies, and in dissipating many doubts. Lastly, he ad- 
mits with M. D’Aubuisson, the complements and rectifications 
which experience has shown to be necessary in the geognostical 
system of Werner. It is with a rapid view of these more re- 
cent observations that I shall conclude this sketch. For this 
purpose, it becomes necessary to fall a little behind in the chro- 
nological order. 
This impulse given by the School of Werner gave rise to 
some remarkable discoveries. Without speaking of the labours 
of the distinguished geologist whom Switzerland has lately 
lost, M. Escher de la Luith, or of those of Von Buch in 
Norway, which shewed, to the great astonishment of the scien- 
tific world, a granite covering rocks containing shells, we ar- 
rive all at once at the discovery of a new class of formations, 
rich in animal remains in rocks and minerals, and still more in im- 
portant truths; I mean the last solid strata deposited at the surface 
of the earth, — the Tertiary Formations ; which were unknown to 
Werner, or which he had confounded with the alluvial deposits «. 
It is to the united labours of Messrs Cuvier and Brongniart, that 
we owe the examination, and, at the same time, the admirable 
description, of these formations, such as they present themselves 
in the greatest development around the capital of France. 
It is not merely as having enriched Zoology with a multi- 
tude of extinct species of almost every class of animals, and Ge- 
ology with several new strata, and especially with general results 
* The statement in the text is not correct, for Werner knew the Tertiary 
rocks, and mentions them under the general title ‘ Partial Formations.’— Edit. 
