DECEMBER 24, 1897.] 
nized by his predecessors, and who en- 
deavored to establish a system of succes- 
sion among them. This led him to a study 
of the denudation which the several lava 
streams had suffered, and thus to the most 
comprehensive statement of the effects of 
erosive action based upon concrete ex- 
amples which had up to that time ap- 
peared. One of the most important con- 
clusions of Desmarest’s investigations in 
the Auvergne was the recognition that 
basalt was of eruptive origin, although he 
found few supporters for his views and did 
not enter later into the prolonged discus- 
sion which arose upon the subject. His 
map of the Auvergne elaborated in great 
detail, although unpublished at the time of 
his death, may still be regarded as his 
greatest contribution to geology, and was 
certainly far in advance of any other at- 
tempt at the cartographic representation of 
geological phenomena of its day. 
Desmarest also contributed four massive 
volumes upon Géographie Physique in the 
famous Encyclopédie Méthodique, and had 
not completed the last at the time of his 
death in his ninetieth year. Cuvier, in his 
biographical sketch of him, says: ‘The 
Academy of Sciences saw in him, as it 
were, the monument of a bygone age, one 
of those old philosophers, now too few, who, 
occupied only with science, did not waste 
themselves in the ambitions of the world, 
nor in rambling through too wide a range 
of study, men more envied than imitated.” 
A factor which added much to the ad- 
vance in scientific thought of last century 
was the rise of the spirit of scientific travel. 
To Pallas (1741-1811), who spent six years, 
from 1768 on, at the head of a scientific 
expedition commissioned by Empress Cath- 
erine II., we owe much important geolog- 
ical information regarding a portion of the 
world then but little known. His study of 
the Ural chain led to his attempt to classify 
the rocks of mountain areas, the chief value 
SCIENCE. 
927 
of his observations lying “in his clear 
recognition of a geological sequence in 
passing from the center to the outside of a 
mountain chain. He saw that the oldest 
portions were to be found along the axis of 
the chain, and the youngest on the lower 
ground on either side.’”’ One of the geo- 
logical questions which especially occupied 
his attention was the occurrence of the re- 
mains of the fossil elephant, rhinoceros and 
buffalo throughout the whole vast basin of 
Siberia, between the Ural and Altai moun- 
tains. 
Few men have better claim to be regarded 
among the founders of geology than de 
Saussure (1740-1799), who was the first to 
arouse the modern spirit of mountaineering, 
and whose indefatigable travels throughout 
the high Alps contributed so largely to the 
stock of ascertained fact which was so use- 
ful as a basis for theoretical speculation. 
To de Saussure we owe the first use of 
the terms geology and geologist, while his 
experiments upon the fusion of rocks, al- 
though only negative results were obtained, 
are especially interesting, as they mark the 
earliest beginnings of experimental geology. 
The third lecture deals with the history 
of the doctrine of geological succession, and 
the influence of Wernerianism upon the 
geological thought of the day. Lehmann, 
Fuchsel and Werner more than any others 
during the latter half of the last century 
advanced the ideas of geological succession. 
Lehmann (died 1767) published, in 1756, 
the first treatise in which a definite attempt 
is made ata chronological classification of 
the rocks of the earth’s crust. He recog- 
nized, from a study of the rocks of the Harz 
and Erzgebirge, three major orders which 
became the Primitive, Secondary and Allu- 
vial divisions of the proposed classification. 
His profiles of the succession of strata 
showed, according to the author, ‘a re- 
markable grasp of some of the essential fea- 
tures of te:tonic geology.’ Contemporary 
