ON TERRESTRIAL MAGNETISM AND ATMOSPHERIC ELECTRICITY. 761 



completely freed from local effects. Taking these values for the three mean stations, 

 he finds the increase of the elements per kilometre of ascent to be as follows : — 



The variations calculated on the assumption that the earth is a uniformly 

 magnetised sphere are much smaller, and the author considers that the discrepancy 

 arises from the fact that part of the magnetic potential of the earth is due to an 

 external source. 



Extracts from the Report of the Permanent Committee on Terrestrial 

 Magnetism and Atmospheric Electricity to the International Meteoro- 

 logical Conference. 



Constitution of the Committee. 



The Committee on Terrestrial Magnetism and Atmospheric Electricity appointed 

 at Paris in September 1896 consisted of eight members. These gentlemen found 

 that it was desirable to add to their number by co-option, and the constitution of 

 the Committee is now as follows : — 



Appointed at Paris: Professor Riicker (President), Professor Eschenhagen, 

 Professor Liznar, M. Th. Moureaux, Sig. L. Palazzo, Dr. Paulsen, Dr. van 

 Rijckevorsel, General RykatcheH'. 



Co-opted: Dr. Bauer, Professor W. von Bezold, Sig. Brito-Capelio, Dr. Carlheim- 

 Gyllenskjold, Professor Mascart, Professor T. Mendenhall, Professor A. Schmidt, 

 Dr. C. Schott, and Professor A. Schuster. 



International Conference. 



In consequence of a suggestion, made originally by Professor Schuster, that 

 arrangements should be made for an International Conference of those interested 

 in Terrestrial Magnetism, the Committee decided to summon such a conference ; 

 and the hospitable invitation of the British Association to hold the meeting in 

 connection with that of the Association at Bristol (September 7-14, 1898) was 

 accepted. 



The details of the arrangements are described in the President's address. 



Meetings of the Permanent Committee. 



The Committee held meetings on September 7, 9, 12, and 1-3, at which the 

 following resolutions were unanimously approved : — • 



A. Questions referred to the Committee by the International Meteorological 

 Conference. 



(1) The following resolution of M. Dufour (Report of Paris Conference, p. 30), 

 ' In calculating monthly means, all days are to be taken into consideration. It 



is left open to each director to give in addition means calculated without taking 

 disturbed days into account.' 



This was approved by the Committee with the substitution of the words ' It is 

 desirable ' for the words ' It is left open to each director.' 



The Committee were also of opinion that the quiet days chosen by the directors 

 of the different observatories should be communicated to the President of the 

 Permanent Magnetic Committee, and circulated by him, and also that it is desirable 

 to inquire if it will be possible to select the same quiet days for the different 

 observatories. 



(2) The resolution proposed bj Professor von Bezold and M. Mascart (Report, 

 p. 31) :- 



' It is desirable to publish the monthly means of the components X, Y, Z, and, 



