ON TERRESTRIAL MAGNETISM AND ATMOSPHERIC ELECTRICITY. 735 



geographical boundaries which sometimes seemed so important in her 

 youth, and that workers for the common good are more and more learning 

 that it is good to work in common. 



But there are special and cogent reasons why the science of Terrestrial 

 Magnetism should be cosmopolitan. The advance of some sciences is 

 most easily achieved by the methods of guerilla warfare. In a hundred 

 diflFei-ent laboratories widely separated workers plan independent attacks 

 on Nature. In different Universities and Colleges little groups are devising 

 stratagems and arranging ambuscades in the hope of wresting from our 

 great opponent some of the treasures which she yields only to the violent 

 who take them by force. But for those who would unravel the causes of 

 the mysterious movements of the compass needle concerted action is 

 essential. They cannot, indeed, dispense with individual initiative, or 

 with the leadership of genius, but I think that all would agree that there 

 is urgent need for more perfect organisation, for an authority which can 

 decide not only what to do, but what to leave undone. 



The advance of the science of Terrestrial Magnetism must depend 

 upon the establishment, the maintenance, and the utilisation of the 

 records of observatories. The bulk of the material to be dealt with must 

 in any case be vast, and every needless addition to it, every obstacle in 

 the way of its being readily comprehended and easily used, is a drawback 

 which proper organisation should prevent. 



Thus it is wasteful to devote to the multiplication of observatories, 

 in regions of which we know much, energy and funds which would be 

 invaluable if applied to districts of which we know little or nothing. I 

 take some credit to myself in that within the last few months I have 

 assisted in checking well-intended but mistaken proposals to add to the 

 number of the magnetic observatories which we already possess in this 

 country. 



Again, it is desirable that the records of the observations should be so 

 published as to be ready for application to the problems the solution of 

 which they are intended to subserve, and that the individual worker 

 should not be harassed by petty diflferences in the methods of presentment, 

 which often entail on him labour too enormous to be faced. On this 

 point something has already been done by international co-operation, and 

 we may hope that this meeting will do much to complete the task. 



Lastly, there are many investigations which are now undertaken 

 independently at irregular intervals which would be far more useful if 

 planned in common. Thus, there has of late been a great outburst of 

 energy in Europe devoted to magnetic surveys more detailed than have 

 ever before been accomplished. Is it too much to hope that when the 

 time comes for these to be repeated they may be carried out simulta- 

 neously, and reduced by the same methods, so that we may have a mag- 

 netic map of Europe in which no uncertainty as to the accuracy of 

 details is introduced by the necessity for correcting for the secular change 

 over long intervals of time 1 



Taking it for granted, then, that international co-operation is desirable 

 for pui'poses such as these, I come next to the question of the nature of 

 the machinery by which it shall be secured. And here I may at once state 

 that the arrangements under which we are meeting to-day are in some 

 respects abnormal, and that plans for the future will have to be formally 

 or informally considered before we part. Meanwhile, it is desirable that 

 I should state precisely the circumstances which have brought us together. 



