478 C. G. Rock wood, Jr. —Japanese Seismology. 
his report to the British Association at its recent fabeitii in 
York, where he states them thus :— 
“1st. The actual back-and- forth motion of the ground is 
seidom more than a few millimeters (usually not equal to one 
oqo pede even though chimneys have fallen. 
“2d. The motion usually commences gently but is very 
irate 
“3d. The number of vibrations per second usually varies 
between three and six 
“4th, During one shock the direction may be irregular. 
“5th. East and west vibrations as recorded at Yedo (Tokio) 
have in some cases fms shown by time observations to have 
traveled up from the so 
“6th. Many of the shisclis which visit Yedo appear to have 
come from a district which is much faulted, and which gives 
evidence of very recent elevation 
This brief and no doubt sasbon piles survey of the field con- 
sidered gives reason to believe that the knowledge of the phe- 
nomena and causes of earthquakes has received and will receive 
important additions through the labors of these residents of 
the far east; and that this youngest of the scientific societies of 
apan, w ose exhibition of seismographical instruments at- 
tracted 2,000 visitors in one day, has such a hold upon pbs 
ee inicldsion T desire to say that for much of the information 
embodied in this paper I am indebted to the kindness of Ee 
John Milne of the Imperial College of Engineering in Toki 
E.—Since this paper was written, the November number 
of the omit Philosophical Magazine has come to hand, con- 
taining an article of 22 pages by John Milne and Thomas 
he on “ Karthquake Observations and Experiments in Japan.’ 
It is a réswmé of work done by the authors during their resi- 
dence "thers, and consists of two parts, the first devoted to a 
pepe g of the instruments used, the second to a discussion 
of the ers ieyse motion. The instruments are described 
under the head of 1. Seismoscopes; 2. Seismometers and 
Seismographs ; a Instruments for vertical motion; 4. Appa- 
ratus on which to record earthquake motions; 5. Time-takers. 
In the second part, the authors discuss the relation of the 
normal and transverse vibrations, the details of the movement 
as illustrated by a copy of the instrumental record made by a 
pair of conical pendulums on July 25th, 1881, the relative 
frequency of earthquakes at different seasons, the effect on 
buildings, and the rotation of bodies. Oo. G. BR. 
Princeton, Nov. 17, 188i. 
