926 
predecessors have encountered, and to real- 
ize what have been the influences that have 
more especially tended to retard or quicken 
the progress of research.” For that pur- 
pose the epoch which extends from the mid- 
dle of the last century to the earlier decades 
of this is especially selected as the period 
when the real foundations of geology were 
laid, although it is freely recognized that 
many honored names in the domain of the 
science antedated this time. 
After referring to the curious coincidence 
of the appearance of the writings of the two 
last anc most eminent of the cosmogonists, 
Leibnitz and Buffon, in the same year dur- 
ing the middle of the last century, the au- 
thor proceeds in most interesting manner to 
describe the life and work of the hitherto 
little recognized Guettard (1715-1786 ), who, 
by his brilliant researches in many lines, 
may be truly called one of the founders of 
modern geology. To Guettard we owe the 
first practical attempt to construct geolog- 
ical maps by depicting the superficial dis- 
tribution of mineral substances. It is doubt- 
ful, however, if he had very definite ideas 
regarding the sequence of formations or of 
geological structure. His map of western 
Europe, so far as it relates to the areas of 
his own observations in France, coincides 
in a broad way with the modern conception 
of the distribution of the stratigraphical 
series, although often erroneously grouping 
younger with older deposits in his‘ bands.’ 
Guettard’s contributions in the field of 
paleontology are also of much significance. 
He recognized the importance of fossils in 
geological research, and published many 
large and elaborate memoirs in which nu- 
merous forms are figured and described. 
He was the first to recognize trilobites. The 
excellence of his descriptions and drawings 
entitle him to rank according to the author 
as ‘the first great leader of the paleontolog- 
ical school of France.’ His memoir ‘On the 
Accidents that have befallen Fossil Shells 
SCIENCE. 
[N.S. Vou. VI. No. 156. 
compared with those which are found to 
happen to Shells now living in the Sea,’ 
which appeared in 1765, is regarded as un- 
questionably one of the most illustrious in 
the literature of geology, as it introduces a 
natural explanation for the phenomena of 
organic remains entombed in the rocks. 
To the field of physiographic geology his 
memoir ‘On the Degradation of Mountains 
effected in Our Time by Heavy Rains, 
Rivers and the Sea’ contributed much and 
must be regarded as one of the classics of 
that department of the science. No one 
had elaborated the subject so fully as he at 
that period. 
The recognition by Guettard of the vol- 
canic origin of the mountains of the Au- 
vergne affords one of the most interesting 
chapters in the whole book. It is one of 
the curious facts connected with his 
remarkable career that these views ‘ prac- 
tically started the Vulcanist camp, and his 
promulgated tenets regarding basalt became 
the watchword of the Neptunists.” It 
seems that he was ‘“‘an indefatigable and 
accurate observer who, gifted with a keen 
eye, well-trained powers of observation, 
and much originality of mind, opened up 
new paths in a number of fields which have 
since been fruitfully cultivated, but who 
rigidly abstained from theory or specula- 
tion.” 
In the second lecture the author discusses 
the rise of voleanic geology as shown by 
the work of Desmarest, and also the begin- 
ning of geological travel by Pallas and de 
Saussure. To Desmarest (1725-1815), a 
public official and astute scientific observer, 
we owe a further elucidation of the geology 
of the classic volcanic district of the Au- 
vergne, which had been the scene of so 
much of Guettard’s labors. Although Guet- 
tard had observed the general volcanic char- 
acter of the district, it was Desmarest who, 
in great detail, traced out the disposition of 
these various rocks and others, unrecog- 
