SEISMOLOGICAL INVESTIGATIONS 259 



1928 was published in July, and that for the fourth quarter was then in 

 proof. 



The following table showing the progress of the Summary has been 

 prepared. The steady increase in the number of pages is mainly due to the 

 growth in the number of well-equipped seismological stations. 



The tables by Dr. Harold Jeffreys referred to in the last report have been 

 published by the British Association, the cost being met by the Gray-Milne 

 Fund. These tables were despatched from Oxford to all recipients of the 

 Summary, as were two papers, one by Dr. Jeffreys alone, the other by 

 Dr. Jeffreys and Dr. Comrie, dealing with the genesis of the tables. 



The new tables are being used together with the accepted Zoppritz- 

 Turner tables in the preparation of the International Seismological Summary 

 for the year 1929. The Summary is to be published in such a form that 

 comparisons between the merits of these and other tables will be facilitated. 



Seismogr.^phs. 

 One of the tasks undertaken by the Seismological Committee in 1895 

 was the development of a seismograph suitable for general use in recording 

 distant earthquakes. The instrument devised by Milne was found to 

 serve its purpose, and a large number of such instruments was distributed 

 to various parts of the world. The principal drawback to the Milne seismo- 

 graph is the absence of any means of damping the oscillations of the 

 pendulum. In 1912 Milne co-operated with Mr. J. J. Shaw in the design 

 of the Milne-Shaw seismograph, a remarkably efficient machine. After 

 preliminary trials the first Milne-Shaw instrument was brought into regular 

 use at Bidston in 1914. Fifty-five Milne-Shaw seismographs have now 

 been constructed. Of these five have been supplied to the Committee. 

 The distribution of these is as follows : 



The machine at Edinburgh was placed originally at Eskdalemuir in 191 5 

 for comparison with the Galitzin seismographs, and was removed to Edin- 

 burgh in 1919. No. I was supplied to Mr. W. E. Plummer at Bidston in 



