2 



On the Propagation of Earthquake Motion. 



I. Vapour-density of Bromine at High Temperatures. By E. P. 

 Perman, D.Sc, and G. A. S. Atkinson, B.Sc. Communicated 

 by Professor Ramsay, F.E.S. 



11. Polytremacis and the Ancestry of the Helioporidse. By J. .W. 

 Gregory, D.Sc. Communicated by Professor Lankester, 

 F.R.S. 



III. Gold-Ahiminium Alloys. By C. T. Heycock, F.E.S., and F. H. 



Neville, F.R.S. 



IV. On the Association of Attributes in Statistics, with examples from 



the Material of. the Childhood Society, &c. By G. Udny 

 Yule. Communicated by Professor Karl Pearson, F.RS. 



V. Data for the Problem of Evolution in Man. III. — On the Magni- 

 tude of certain Co-efficients of Correlation in Man, &c. By 

 Professor Karl Pearson, F.R.S. 



" On the Propagation of Earthquake Motion to great Distances." 

 By R. D. Oldham, Geological Survey of India. Communi- 

 cated by Sir Robert S. Ball, F.R.S. Received June 16, — 

 Read November 16, 1899. 



(Abstract.) 



When preparing a report on the great Indian earthquake of 12th 

 June, 1897, the author noticed that the European records of this 

 earthquake showed a phase of increased disturbance in what are 

 commonly called the preliminary tremors, making, with the great un- 

 dulations, three phases of motion. He suggested that these three 

 phases represented the arrival of (1) the condensational, (2) the dis- 

 tortional waves travelling through the earth, and (3) surface undula- 

 tions travelling round the earth. The present paper is an attempt to 

 verify these suggestions by a comparison with other earthquakes. 



For this purpose a selection has been made from the published 

 records of those earthquakes which fulfil the conditions (1) that the 

 place of origin shall be known within 1° of arc, (2) that the time of 

 origin shall be known within a limit of error of one minute, (3) that 

 there shall be a sufficient number of records, distant more than 20° of 

 arc from the origin, to serve as a check on each other. Eleven distinct 

 shocks, representing seven great earthquakes, are found to satisfy 

 these conditions, and in every case the same three-phase character 

 as was recognised in the earthquake of 12th June, 1897, is found. A 

 comparison of time intervals and apparent rates of propagation shows 



