470 C. G. Rockwood, Jr.—Japanese Seismology. 
respect to the seasons, the motions of sun and moon, the fre- 
quency of sun-spots, meteors, etc. ; and Professor Chaplin * has 
examined in the same way the records for three years (1875-8) 
of the Palmieri instruments in the Meteorological SHE SEEPIONY. 
of Tokio. But the results are entirely negative, not confirm 
ing Professor Alexis Perry’s deductions from a similar exam- 
ination of his lists, although Hattori and Ayrton both think 
they one some indications of a periodicity in _ destructive 
shoe 
Piades examining native records, much attention has been 
given to the instrumental Pe Peation of the earth-motion. 
In this work Perry and Ayrton, Wagner, Chaplin, Ewing, 
Gray and Milne have all had a part 
The devices area et by former gota, have been here 
tested anew. Pendulums long an ort, suspended and in- 
verted, with bobs light and heavy, and making their records 
by seratching a smoked plate, by pushing light “rods arranged 
against them, or by pulling cords and turning pointers over 
graduated arcs, the fluted mercury dish of Cacciatore, the 
graduated cylinders of Robert Mallet, and the bent tubes and 
loaded ae of Palmieri, as well as the microphone sug- 
gested by Rossi have all been employed and have done good 
service 
But no one of these was entirely satisfactory. Not to men- 
tion aes difficulties, the pendulums and loaded springs had 
each a normal rate of vibration, aid were ready to take up 
and accumulate earth vibrations ‘of similar rate, while remain- 
ing to a considerable extent unaffected by those of a different 
period. So that the records of the earth-motion were compli- 
cated or perhaps entirely concealed by those due to the normal 
pian of the apparatus. This difficulty, long known, was 
tated and mathematically discussed by Perry and “Ayrton i in a 
er read before the Asiatic Society of Japan in 1877 and 
afterward Asean + The remedy suggested by them was to 
support a heavy ball within an iron box, by spiral springs of 
such stiffness as to make its normal rate of vibration much 
quicker than any ordinary earthquake wave. 
Moreover, while these instruments of former observers gave 
some more or less accurate indication of the time of an earth- 
* Examination of the Barthqualkes tego at the Meteorological Observatory 
of Tokio. Transac. Asiatic Soc. o an, vol. vi, pa 
+ On a negiected principle that may Ds employed i in Earthquake Measurements. 
London Phil. Mag., V, vol. viii, p. 30, July, 1879. 
