608 
could the exact age of a number of trees be 
determined. This has been planned for 
future work and will be executed at the 
earliest possible date. The fact, however, 
that these trees have acted as silent guards 
for centuries over these slopes and have re- 
corded with unerring accuracy the rate of 
erosion is apparent, and as soon as the data 
can be secured, there will be a valuable 
factor for converting geological time into 
years. 
By approximating the various estimates 
in connection with the date the following 
may be of interest: The Hole where the 
observations were made was about six 
miles wide. The trees were 300 years old 
and there had been on an average of three 
feet of rock removed from their roots. This 
would require one hundred years to remove 
a foot of the formation. Considering that 
the erosion started in the center of the Hole, 
there has been three miles removed from 
either side, which at the rate of one foot 
per century would require 1,584,000 years. 
Without question this erosion commenced 
at the close of the Miocene and hence 
represents the entire Pliocene and Pleis- 
tocene Epochs. The exact time relation of 
the Pliocene, and Pleistocene in relation to 
Eocene and Miocene has not been estab- 
lished ; but if the Pliocene and Pleistocene 
Epochs represent 1,584,000 years it would 
not be out of the way to estimate Ceno- 
zoic time at 4,000,000 years. If this 
value be substituted in the ratios of geolog- 
ical time suggested by Dana :—Paleozoic: 
Mesozoic: Cenozoic as 12: 3:1 then all 
geological’ time since the beginning of the 
Cambrian would be represented by 64,000,- 
000 years. This estimate is not inconsistent 
with some already made ; but when founded 
on absolute data may vary much from this. 
Nevertheless, whatever the results may be 
when found upon a complete investigation 
of this subject, they will furnish valuable 
scientific data that will aid materially in 
SCIENCE. 
[N. 8S. Von. X. No. 252. 
giving us a better understanding of geolog- 
ical time in terms of years. 
WILBuR C. Kyieur. 
GEOLOGICAL LABORATORY 
UNIVERSITY OF WYOMING, 
October 2, 1899. 
SCIENTIFIC BOOKS. 
La géologie expérimentale. Par StANISLAS MEu- 
NIER, Professeur de Géologie au Museum 
d’histoire naturelle de Paris. With 56 fig- 
ures in the text. Paris, Ancienne librairie, 
Germer Bailliére et cie. 1899. Pp. 311. (Bib- 
liothéque Scientifique Internationale, XCII.). 
Price, 6 frs. 
Just twenty years have elapsed since Dau- 
brée brought out his famous work Etudes syn- 
thétiques de géologie expérimentale, and laid 
thereby the foundations of the school of French 
experimentalists. This book was translated 
into German in the following year, 1880, but 
never found an English interpreter. That such 
an edition was needed is shown by the refer- 
ence in Dana’s Manual of Geology to an alleged 
experiment of Daubrée with plates of ice, which 
should have been rendered plates of glass. 
The mantle of Daubrée seems to have been 
taken up by M. Stanislas Meunier, who enjoys 
the distinction of having reduced the odds and 
ends of experiments, performed in the imitation 
and illustration of geologic processes, to a sys- 
tem of lectures for the entertainment and in- 
struction of a large class of students. The 
present book is a résumé of these lectures as given 
in the year 1898 at the Museum of Natural 
History in Paris. 
The scope of the work is general, in that the 
experiments described relate to a wide range 
of phenomena, e. g., the formation of rain- 
prints, stream channels, deltas, solution furrows, 
weathering, disintegration and decomposition 
of rocks, the striation of rocks, sedimentation 
under varied conditions, the production of 
faults, folds, and systems of fracture and dis- 
placement. The treatment of the subject, how- 
ever, is somewhat narrowed by the fact that. 
the author deals almost altogether with his own 
experiments, with only incidental reference to 
the work of others. The book cannot be said, 
therefore, to represent fairly or comprehen- 
