ON SEISMOLOGICAL INVESTIGATIONS. 61 



to the disturbance which on the 17th of that month destroyed Valparaiso. 

 The omission is due to the fact that the original seismogram had been 

 loaned to the International Seismological Association, and was not 

 returned in time for publication in its right place. It, however, appears 

 in Circular 17. 



In other cases also the International Seismological Association have 

 communicated directly with stations which for some years past have 

 kindly co-opei-ated with the British Association. The result has been 

 that serious inconvenience has been experienced. In connection with this 

 attention may be drawn to the following resolution of the Council of the 

 Royal Society of London, dated December 6, 1906 ; — 



' Eesolved — That the Council are of opinion that no change should bo 

 }nade in the practice whereby all seismological reports and observations 

 for the United Kingdom are collected and transmitted by Professor Milne.' 

 It is fully recognised that every station which has kindly given assist- 

 ance to the British Association Seismological Committee is an independent 

 unit, and will therefore act upon such lines as seem best fitted to advance 

 seismological investigation. 



All circulars issued by the British Association Committee are sent 

 not only to cooperating stations, but to others who express a wish to 

 receive them. It has been thought advisable, however, not to send original 

 seismograms anywhere by post, since on several occasions these have been 

 lost. As far as possible photographic copies are sent to those who desire 

 them. 



Instruments. — In January and February 1907 two single-boom instru- 

 ments were despatched to Capt. H. G. Lyons, Director-General Survey 

 Department, Egypt. Each gives an open diagram (similar to Plate II.), 

 and is oriented at right angles — one recording JST.S. motion and the other 

 E.W. motion. The station is at Helwan, near Cairo. 



On January 21 a similar instrument was forwarded to W. G. Davis, 

 Esq., Director of the Argentine Meteorological Observatory at Buenos 

 Ayres. In October a fourth instrument, also giving an open diagram, was 

 despatched to the order of the Agent- General for South Australia, to 

 Adelaide. 



In May 1908 a single-boom instrument was forwarded for the Cosego 

 del Servicio Geografico, Madrid ; while in J une a twin-boom seismograph 

 was constructed to be used by the National Physical Laboratory in their 

 new station at Eskdalemuir, South Scotland. 



Catalogues. — Considerable time has been spent in cataloguing the 

 papers and books which relate to earthquake phenomena. Those in the 

 English language have been completed, and Mr. O'Neill is now engaged 

 upon those in foreign languages. 



Time Signals. — The clock which gives us the time for the instruments 

 at Shide is regulated by a Greenwich signal which is sent daily to all 

 chief post offices throughout Great Britain. From time to time this 

 signal, which is not visible to the public, is kindly given to me by the 

 officials at the General Post Office at Newport. This involves a 

 journey of two miles. To avoid this, and to assure greater accuracy, an 

 attempt was made to obtain this signal at Shide. With this object 

 in view the Astronomer-Royal, and subsequently the Council of the 

 British Association, wrote to the Postmaster-General. It was pointed 

 out that the observatory at Shide ' has been of universal interest and of 

 recognised public importance. This station serves a-s a centre for stations 



