OEODETIC COMMITTEE. 



29 



Determinations of gravity have been made in the United Kingdom, 

 Egypt, and at numerous coast stations, and form part of the regular work 

 of the Survey of India and are desirable in other parts of the Empire. 



Geodetic work must foi-m the basis of the control of all the State 

 Surveys of the Empire, on which about a million sterling was being spent 

 annually before the war. 



An institution in which the results of such work in all parts of the 

 Empire would be systematically collected and reviewed, where the 

 methods and instruments were discussed, and where the corresponding 

 work of other nations would be regularly brought into relation with it, 

 would be of great value to all these State Surveys. 



Tides. 



4. The navigational applications of tidal phenomena are provided 

 for by the Hydrographical Department of the Navy, but there is a 

 part of the subject which is closely related to Geodesy and especially 

 to precise levelling. 



Oceanic tide gauges are maintained in the United Kingdom (3), 

 India (9), Canada (4), New Zealand (2), and Australia (1), and their 

 data, which are utilised for providing tide-tables, are valuable also in 

 discussions of sea-level, reference data, and the movements of the crust 

 of the earth. The work of correlating these observations in different 

 countries could be very suitably undertaken in an institution devoted 

 to Geodesy and allied subjects. 



Seismology. 



5. While there are nine places in the Empire where seismographs 

 exist capable of furnishing data for the determination of the physical 

 properties of the earth, there is a widely spread network of stations 

 equipped with a simpler form of seismograph, which was instituted and 

 developed by the late Professor J. Milne, F.E.S. These stations are 

 situated in all parts of the Empire and also in some foreign countries. 

 During Professor Milne's lifetime he received and discussed the records 

 of all these stations, and practically maintained a Seismological Institute, 

 so far as these instruments were concerned, in the Isle of Wight. Since 

 his death the work has been carried on by the Gom<mittee of the British 

 Association, of which he was formerly Secretary. 



6. It seems to the Committee that there are two classes of require- 

 ments to be considei'ed : — 



(1) The need for a few first-class seismological stations, equipped 



with the best type of seismographs and established in 

 different parts of the Empire, to record the vibrations caused 

 by earth shocks which affect the earth as a whole; and 



(2) The study of earthquake frequency, crustal movement, and 



local earthquake phenomena genei-ally. which may be 

 studied with simpler forms of instrument and under local 

 arrangements. 



In the United Kingdom one first-class station would probably suflBce, 

 and this might form part of the Geodetic Institute, since the equipment 



