930 
and divided the limestones into five epochs 
or ages, the strata in each of which are 
marked by a distinct assemblage of fossil 
shells. He thought, however, ‘that the 
most ancient deposits had been accumula- 
ted at the highest levels, when the sea cov- 
ered the whole region, and that, as the 
waters sank, successively younger forma- 
tions were laid down at lower and lower 
levels,’”’ and ‘“‘he felt confident that if the 
facts observed by him in the Vivarais were 
confirmed in other regions a historical 
chronology of fossil and living organisms 
would be established on a basis of incontest- 
able truth.” 
Cuvier (1769-1832) and Brongniart 
(1770-1847) together studied in much de- 
tail the Tertiary formations of the Paris 
basin. They demonstrated in this area 
‘the use of fossils for the determination of 
geological chronology and they paved the 
way for the enormous advances which have 
since been made in that department of our 
science.’ They brought forward clearly the 
evidence for ‘a definite succession among 
the strata and the distinction of the organic 
remains contained in them.’ Cuvier had 
already shown that the fossil elephant found 
near Paris belonged toa different species 
from either of the living forms, and by fur- 
ther research reconstructed the skeletons of 
other types, which enabled him to announce 
‘the important conclusion that the globe 
was once peopled by invertebrate animals 
which, in the course of the revolutions of 
its surface, have entirely disappeared.’ 
The work of Cuvier and Brongniart upon 
the Tertiary formations has been but little 
altered, although greatly elaborated. The 
broad outlines sketched by them remain as 
true now as they were when first traced by 
them early in the century. 
D’Omalius d’Halloy extended the work of 
his predecessors among the Tertiary forma- 
tions, but, what is of more interest, ‘recog- 
nized the leading subdivisions of the Cre- 
SCIENCE. 
(N.S. Vou. VI. No. 156. 
taceous series and actually showed the ex- 
tent of the system upon a map. This map 
is regarded as the first attempt to construct 
a true geological map of a large tract of 
France,’ which was something more than 
‘a mere chart of the surface rocks.’ It 
was provided with a horizontal section 
showing the structural relations of the for- 
mations. ° 
In England, Michell is regarded as the 
first to present anything like a clear idea of 
stratigraphical sequence, a table giving the 
broad features of the succession of strata 
from the Coal Measures of Yorkshire up to 
the Chalk, having been drawn up by him 
about1788 or 1789. Geikie very clearly points 
out, however, that ‘the establishment of 
stratigraphy in England, and of the strati- 
graphical sequence of the Secondary, or at 
least of the Jurassic, rocks for all the rest 
of Europe, was the work of William Smith,” 
a land surveyor, usually known as the 
‘Father of English Geology.’ ‘No more 
interesting chapter in scientific annals can 
be found,” according to the author, “ than 
that which traces the progress of this re- 
markable man, who, amidst endless obstacles 
and hindrances, clung to the idea which 
had early taken shape in his mind, and 
who lived to see that idea universally 
accepted as the guiding principle in the in- 
vestigation of the geological structure, not 
of England only, but of Europe and of the 
globe.” Smith made no attempt to publish 
his results, although he accumulated a vast 
store of notes upon his observations during 
his journeys in the pursuit of his profession. 
His ideas gradually became widely known, 
and a card of English strata from the Coal 
to the Chalk, drawn up in 1799, though not 
actually published, obtained wide publicity. 
His geological map of England and Wales 
with part of Scotland, in fifteen sheets, re- 
garded as one of the great classics of geo- 
logical cartography, and upon which he 
had been at work for many years, was not 
