26 NATIONAL ACADEMY OF SCIENCES 



As regards terrestrial magnetism, I have only a few words 

 to say. 



Through the magnificent efforts of the Carnegie Institution 

 of Washington, we are at last likely to have a satisfactory mag- 

 netic survey of the world, but important as the results obtained 

 by Professor Bauer in the " Carnegie" will prove to be, they 

 will have to be supplemented by systematic observations of the 

 variations of the magnetic forces at a number of fixed stations. 

 Many such stations are in existence, though they are very irreg- 

 ularly distributed over the surface of the earth. 



In this subject, almost more than in any other, an international 

 agreement on the manner in which the records are to be treated 

 and published is essential, and it is much to be regretted that the 

 attempts that have been made to reach such agreements have not 

 met with greater success. There are, no doubt, peculiar diffi- 

 culties due to differences in the organization of the magnetic 

 services. 



Methods have developed independently in different countries, 

 and there is a natural but regrettable reluctance to alter an instru- 

 mental detail or a peculiarity in treating the observation until 

 the necessity of the change has been demonstrated. But that can 

 never be done, because practically all methods are equally good. 

 What is bad is that they differ. Almost any one of these methods 

 could be adopted with advantage anywhere; so that a discussion 

 of which of the methods is better than the other is futile. The 

 first essential then is that in every place on earth the same 

 methods should be adopted, because the least difference in them 

 may cause important errors in the deductions when they come to 

 be compared with each other. 



The only body which at present deals systematically with the 

 records of terrestrial magnetism is a sub-committee of the Meet- 

 ing of Directors of Meteorological Observations. The Directors 

 of Meteorological Observations meeting at intervals have ap- 

 pointed a certain number of sub-committees dealing with a cer- 

 tain number of subjects. Some of these overlap other associa- 

 tions already. So that, for example, the question of solar radia- 



