A.— MATHEMATICAL AND PHYSICAL SCIENCES. 17 



country or distributed over the surface of the earth, is known to be 

 essential for its solution, not only is it necessary to maintain the most 

 intimate contact between the workers, but it is also necessary to plan 

 much of the work as if it were under single control. The International 

 Union of Geodesy and Geophysics is the body to which we must look not 

 only to co-ordinate the work of the various magnetic observatories but to 

 plan lines of attack, and ensure, so far as is practicable, that the 

 accumulated results are such as would be obtained under single control. 

 While my object to-day is not to put forward any programme for the 

 consideration of the International Committee of Geodesy and Geophysics, 

 I do make a plea for the adoption by many of the first-class magnetic 

 stations of a programme including observations at the same times and with 

 similar instruments of great sensitivity. As an illustration of what might be 

 done, take the question of the simultaneity of occurrence the world over 

 of a large magnetic storm. We know such storms affect the instruments 

 of most of the magnetic observatories of the world, and two views have 

 been advanced with regard to the time of commencement of such dis- 

 turbances ; one that a disturbance occurs simultaneously at all stations, 

 and the other that there are time differences of the order of a few minutes. 

 A definite answer to the question, ' Are there such time differences and 

 what is their magnitude,' could be given within a year or less if a few 

 chosen observatories were equipped with precisely similar quick-running 

 magnetographs in addition to their slow-running ones, and time was 

 automatically recorded on the charts every minute. To eliminate, or 

 at least reduce to negligible dimensions, any error due to differences in 

 the time bases of reference, wireless time signals should also be auto- 

 matically recorded on the charts. Some fifteen years ago I had the task 

 of recording the magnetic disturbances due to an electric train system, 

 and it was found possible to correlate the magnetic disturbance and the 

 starting of an electric train more than a mile away, with an error not 

 greater than one second. When one considers the praiseworthy work of 

 Bauer and others on vertical earth-air electric currents, it is apparent that 

 their labours would have been tremendously simplified and their con- 

 clu.sions of much greater value had all the instruments used been precisely 

 similar and a definite programme laid down. 



Lest I be misunderstood, I wish to emphasise the undesirability of 

 magnetic observatories being all alike and all similarly equipped. Each 

 observatory should have its own particular problems and its own special 

 methods of attacking them and thus preserve its individuality but, in 

 addition, part of the equipment should be of an international type and 

 part of the programme should be of a truly international character. 



The early investigators showed that the causes of the earth's 

 magnetism and its variations were problems of great complexity, and the 

 first line of attack was naturally to accumulate data. For the work done 

 no one can fail to have admiration, and particularly I wish to pay tribute 

 to the internatioDal work of the Department of Terrestrial Magnetism of 

 the Carnegie Institution of Washington, and to express regret at the 

 destruction by fire of the non-magnetic ship ' Carnegie ' and the loss of 

 life caused thereby. The untimely death of Captain Ault, the master^ and 

 chief of the scientific personnel, is greatly regretted. 



1930 C 



