388 The American Geolo(/ist. June, 1895 
tr^'s contribution could be summarized in like maniu'r. It is of great 
value to workers outside of Hritain, where the si)ecial literature of Brit- 
ain is less accessible. The editor's introductorj- review is the most 
valuable single part of the volume, especially to geologists not rtjsident in 
llritaiii. It maj' be objected that necessarily such a review is tainted 
by the coloring which it may receive from the reviewer's own ideas. 
But that we do not deem a fault. Every competent geologist is entitled 
to his opinion and to the right to make it etfective, and anj' geologist 
who by great labor contributes to the general fund and to the clearness 
of the geological ideas current in his day, is a benefactor to the science. 
He should not be requii'ed to renounce his individuality nor to smother 
his sentiments. Besides, if any geologist puts himself under the burden 
of annually condensing and publishing the work of Britisli geologists, 
he should be accorded the [iresumptive possession of geological acumen 
sufticient to guide him, and a sufficiently high sense of fairness to make 
him render justice in his judgments. He must be a geologist who is 
personally devoted to the cause of geology and to hard work. If he 
have his own ideas on some geological questions the}- will be pretty 
likely to be grounded on the best of evidence. 
This is the fourth volume of this series, which began with the year 
1890. The four vt)lumes are sold at thirty shillings. n. h. av. 
Results of a Transcontinental Series of Gravity Measurements. By 
Georgk Rockwell Putnam. Notes on the Gravity Determinations Re- 
ported by Mr. G. R. Putnam. By Grove Karl Gilbert. (Philosophi- 
cal Soc. of Washington, Bull. vol. 13, pp. 81-7fi, pi. 5, April, 1895.) 
Some important geodelical work has been recently undertaken by Mr. 
G. R. Putnam in connection with the United States Geological Survey 
in the carrying out of a series of pendulum e.vperiments to determine 
the force of gravity at various points in North America. This subject 
has received much attention from physical geologists, especially since 
the publication of the results of Maskelyne's experiments on Schehal- 
lion, and later of those of Pratt in the Himalayas and of Airy in a coal 
mine in the north of England. Pratt's results seem to indicate that the 
material of th(i Himalayas was of less specific gravity than the adjoin- 
ing crust, so that the deviation of the plumb line from the true vertical 
was less than it should hate been had the density of both been equal. 
The difficulty and cost of the necessary experiments have in the past 
been a great barrier in the way of physicists who desired to repeat and 
extend them. But by the employment of a half-second or quarter-me- 
tre pendulum these obstacles were so far reduced as to render the task 
one of comparative ease, and twenty-six stations were occupied and ob- 
servations made at each of them during five months of 1894. 
A statement of his results is given by Mr. Putnam in a tract pub- 
lished by the Philosophical Society of Washington, and f'uUowing it is a 
short discussion of the results hy Mr. G. K. Gilbert. 
Elaborate corrections are applied to the figures obtained by observa- 
tion whereby they are reduced to those for latitude 40° and to sea-level, 
