518 Reviews—J. Hall & J. M. Clarke—Paleozoic Brachiopoda. 
lengths, not altogether unlike the swell upon an ocean. In period 
they range from one to four or five seconds, their maximum slope 
being roughly from 1 in 200,000 to 1 in 40,000, 2.e. from about 
1”to5”. He believes that they may be due to fluctuations in atmo- 
spheric pressure, acting over considerable areas of the earth’s crust, 
not necessarily taking place at the spot where the fluctuations are 
observed; for, as he shows, the pulsations if produced in this 
manner might outrace their cause. ‘Towards the end of the paper, 
Prof. Milne discusses the possible connection of earth-pulsations 
with the rate of escape of fire-damp in mines. He also shows that 
the zero of a delicate balance may be temporarily altered by earth- 
pulsations, and that consequently in weighing by the “ method of 
vibrations” the results may be slightly inaccurate. In the same 
Way, errors may perhaps occur in pendulum experiments and in the 
delicate work of astronomical observatories. 
(16) Mr. F. Omori summarizes the accounts which he has collected 
from histories and chronicles of 908 shocks, or groups of shocks, 
felt in China previously to the year 1644. Two districts are 
especially characterized by earthquakes, one consisting of the three 
northern provinces of Kansu, Shense, and Shanse, which have often 
been the seat of extensive and violent earthquakes; the other, the 
south-western province of Ytinnan, where the shocks are mostly 
local. These Mr. Omori considers to be distinct seismic regions, 
for they show no coincidence in their epochs of maximum disturbance. 
The meizoseismal area of several earthquakes, he finds, was an 
elongated valley tract, and in such cases the disturbed area was 
generally extended in a perpendicular direction. 
C. Davison. 
Ii.—Patzontotocy oF New York, Vol. VIII. Part IJ. Fascicle I. 
An Introduction to the study of the genera of the Paleozoic 
Brachiopoda. By Jamus Hatt, assisted by Joun M. Crarxe. 
Albany, New York, July, 1893. (Charles Van Benthuysen & 
Sons.) 
WING to unavoidable delay in printing the lithographic plates 
designed to accompany the second volume of Hall and Clarke’s 
monumental work on the genera of the Paleozoic Brachiopoda, the 
authors deemed it advisable to issue a part of the edition in the form 
of fascicles. The first of these was published in July last and treats 
exclusively of the spire-bearing genera. It contains 176 pages of 
text, accompanied by numerous woodcuts, and although it lacks the 
illumination of the plates we welcome its appearance gladly as a 
further instalment of the excellent work that has already effected 
a revolution of thought in the world of brachiopodists. 
The method and text of the first fascicle of the second volume are 
as excellent as those of the first. The subject-matter called for less 
rigorous treatment, as the various spire-bearing forms had been 
carefully investigated by Dr. Davidson, by the light of the Rev. 
Norman Glass’s excellent preparations of the variously modified 
spiral calcified supports of the brachial organs. The Carboniferous 
~~) 
