ON SEISMOLOGICAL INVESTIGATION. 161 
Seismological Investigations—Fourth Report of the Convnittee, con- 
sisting of Professor J. W. Jupp (Chairman), Mr. Joun MILNE 
(Secretary), Lord Ketvix, Professor T. G. Bonney, Sir F. J. 
BraMweE.t, Mr. C. V. Boys, Professor G. H. Darwiy, Mr. Horace 
Darwin, Major L. Darwty, Professor J. A. Ew ING, Professor C. 
G. Kyort, Professor 2. Metpova, Mr. R. D. OLpHAM, Professor 
J. Perry, Professor J. H. Poynting, Mr. Clement Rem, Mr. 
G. J. Symoys, and Prof. H. H. Turner. Drawn up by the Secretary. 
CONTENTS. 
PAGR 
I. On Seismological Stations already established. By J. MILNE . . L6L 
Il. Notes respecting Observing Stations and Registers obtained from the same. 
By J. MILNE . : : c 3 . 162 
JIL. Discussion af the Preceding Register 8, ” By np MILNE ‘ ; . 192 
IV. Earthquake Varieties and Earthquake Duration. wh J. MILNE : . 225 
V. Larthquake Echoes. By J.MILNE . : : : Per As 
VI. Larthquake Precursors. By J. MILNE . : = ; . 230 
VII. Larthguake and eee Disturbances. By J. MILNE : . 233 
VIII. Form of Reports . - : : : : : . 233 
I. On Seismological Stations already established. 
InstRuMENTS of the same type have been forwarded to the following 
twenty-three stations :—Shide, Kew, Toronto, Victoria, B.C.,San Fernando 
(Spain), Madras, Bombay, Calcutta, Batavia, Mauritius, Cape Town, 
Arequipa, Strathmore College (Philadelphia), Tokio, Cordova (Argentina), 
New Zealand (two instruments), Cairo, Paisley, Mexico, Beyrout, Hono- 
‘lulu, and the last to Trinidad. 
It is expected that shortly instruments will be installed in Ireland, 
New South Wales, and Victoria, and your Secretary has had correspondence 
about the establishment of seismographs in other countries. 
The following Report contains registers from the first eleven of the 
above- mentioned stations, and reports ‘tr om several of the remainder are 
expected to arrive shortly, 
The principal analysis of these registers has been made in reference to 
the one from Shide, but as many earthquakes have been recorded which 
did not reach that station, but were common to groups of observatories in 
other parts of the world, it is evident that if similar analyses are made in 
reference to other localities, our knowledge respecting the distribution of 
seismic disturbances will be largely increased. Should any of the observers 
who have forwarded copies of their observations to Shide consider it 
advisable to undertake this work, it is hoped that this report will be of 
assistance in carrying out the same. 
The Committee thank the Directors of observatories in Italy, Germany, 
and Russia for copies of records corr esponding to those obtained in Shide. 
For the purpose of seeing the installation in the Isle of Wight and dis- 
cussing records, Shide bas been visited by Colonel Gore, R.E., of the 
Trigonometrical Survey of India, Mr. R. D. Oldham, of the Geological 
Survey of that country, Dr. Figee, i in charge of the instrument in B: wtavia, 
Mr. a Claxton, Director of the Observat tory in Mauritius, Dr. F. 
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