May 13, 1910] 



SCIENCE 



757 



volved, either stopping such importation or pro- 

 viding such inspection and quarantine laws as are 

 best adapted to the situation. 



C. L. Sheae, 

 Secretary- Treasurer 

 (To be continued) 



SOCIETIES AND ACADEMIES 



THE PHILOSOPHICAI, SOCIETY OF WASHINGTON 



The 679th meeting was held on April 9, 1910, 

 Vice-president Fischer in the chair. Two papers 

 were read. 



Times of Abruptly Beginning Magnetic Disturb- 

 ances as Recorded at the Coast and Geodetic 

 Magnetio Observatories: R. L. Faris, of the 

 Coast and Geodetic Survey. 

 The speaker gave a brief review of the re- 

 searches that had heretofore been made by investi- 

 gators concerning the sudden beginnings of mag- 

 netic storms, with special reference to their times 

 of beginning at different places, the general im- 

 pression hitherto being that they are simultane- 

 ous, or so nearly so, all over the earth that the 

 time scales of the records were too small to war- 

 rant any other conclusion. Dr. L. A. Bauer 

 having recently found that there is a definite time 

 element in the propagation of the magnetic dis- 

 turbance in some special cases investigated by 

 him, the speaker, at his suggestion examined a 

 number of cases of suddenly beginning magnetic 

 disturbances recorded at the Coast and G«odetic 

 Survey magnetic observatories, which cover a 

 quarter of the globe in longitude, with the result 

 that the investigation showed that there is a 

 persistent time difference for the storm begin- 

 nings at different places which is too large to be 

 attributed to errors in the time determinations, 

 thus confirming the results of Dr. Bauer's recent 

 investigations. 



The paper will appear in full in the June, 1910, 

 number of the Journal of Terrestrial Magnetism 

 and Atmospheric Electricity. 



On the Analysis and the Propagation of Magnetic 

 Disturbances : Dr. L. A. Bauee, of the Carnegie 

 Institution of Washington. 



An examination of the times of beginning of the 

 magnetic disturbance which occurred on May 8, 

 1902, as coincidently with the Mont Pel6 eruption 

 as can be determined, revealed the interesting 

 fact that they were not the same all over the 

 globe, being, in general, earliest at European 

 stations. The times next progressed going around 

 the earth eastwardly, the complete circuit being 



made by the disturbance in about three and one 

 half minutes. This fact led to an examination of 

 other similar disturbances, such as the one of 

 January 26, 1903, and it was again seen that this 

 one also progressed around the earth eastwardly, 

 the time for the complete circuit being about 

 four minutes. 



Mathematical analyses were next made and it 

 was found that for both disturbances (May 8, 

 1902, and January 26, 1903) the systems of dis- 

 turbance forces which it would be necessary to 

 superpose upon the earth's own magnetic field, 

 were precisely of the same character as the 

 earth's. In other words, were we to assume elec- 

 tric currents as forming the disturbance systems, 

 then, as is the ease for the earth's field, the 

 currents would have to circulate around tlie earth 

 from east to west if they are positive ones, and 

 in the contrary direction — from west to east — if 

 they are negative, or such as would be produced 

 by moving negative charges. Furthermore, for 

 both disturbances the electric currents would liave 

 to circulate chiefiy in the regions above the earth. 



For the disturbance of May 8, 1902, there were 

 a sufBcient number of reliable determinations of 

 the effect on the vertical intensity and accordingly 

 it was possible, by means of the analysis, to sepa- 

 rate the external system of currents from the 

 internal (below the surface) one. And then the 

 surprising result revealed itself, that the internal 

 currents went in the same direction as the ex- 

 ternal ones, the latter being of about three times 

 the strength of the former. Hence, were we to 

 suppose that the disturbance is caused by the 

 motion of negative charges around the earth 

 eastwardly, then the internal negative currents 

 also go in the same direction and, accordingly, 

 they are not currents induced in the earth by the 

 outer system. 



If the earth's own magnetic field is likewise 

 separated into an internal system and an external 

 one, it is also found that for both systems the 

 negative currents go in the same direction around 

 the earth, viz., from west to east. The disturb- 

 ance systems found above are therefore precisely 

 similar in character to the earth's field. It should 

 also be noted that the direction of the disturbance 

 negative currents progress around the earth in 

 the same way as did the times of beginning 

 referred to above. The assumption is therefore a 

 natural one that such disturbances as here in- 

 vestigated, which Birkeland in his recent impor- 

 tant work^ called " equatorial perturbations," 



' Birkeland, Kr., " The Norwegian Aurora Po- 



