NOVEMBEE 11, 1904.] 



SCIENCE. 



643 



the cause is to be sought in the distribu- 

 tion of temperature in the upper stratum 

 of the earth's crust, as produced largely 

 by the distribution of land and water. 

 The results of the decomposition have thus 

 revealed one promising mode of attack of 

 the problem as to the causes of the asym- 

 metrical distribution of the earth's mag- 

 netism. 



Another extremely interesting residt is 

 that a very close similarity is found to exist 

 hettueen the chart of the residual perman- 

 ent magnetic field and that of the system 

 of forces causing the diurnal variation of 

 the earth's magnetism. The two magnetic 

 systems are identical in their general char- 

 acteristics except in one respect, viz., the 

 first is to be referred to a system of mag'- 

 netic forces in the earth's interior, whereas 

 the second to a system outside, the relative 

 positions of the poles being governed ac- 

 cordingly. Thus at Greenwich mean noon, 

 for example, the north end attracting pole 

 of the first system would be about vertically 

 below the south end attracting pole of the 

 second system, and the south end attracting 

 pole of the first would be about directly 

 below the north end attracting pole of the 

 second system— this statement holds for 

 the main transverse magnetization in each 

 hemisphere. 



There appears to be more than a chance 

 connection in this relation, as is shown by 

 the horizontal vector diagrams for various 

 parallels as resulting from the two respect- 

 ive fields. 



I have had the impression for some time 

 that the earth's permanent magnetic field 

 may play a very important part in the 

 production of the diurnal variation field as 

 observed on the earth's surface. No satis- 

 factory explanation has as yet been given 

 of the manner in which the peculiar mag- 

 netic system of forces causing the diurnal 

 variation is actually produced. Schuster's 

 first attempt at the construction of the 



equipotential lines of the diurnal variation 

 field, based as it was on exceedingly meager 

 data, was, nevertheless, remarkably correct 

 in its general features, as shown by the 

 recent more elaborate work of Fritsehe. 

 We, therefore, have now a fairly accurate 

 map of this field. 



The existence of some form of radiation 

 from the sun which does not penetrate to 

 the lowest strata of our atmosphere, and 

 which is yet capable of deflecting magnetic 

 needles on the earth's surface, appears to 

 have been definitely proved by the recent 

 magnetic observations during solar eclipses. 

 It was, furthermore, shown that the eclipse 

 magnetic variation was a phenomenon 

 similar to the diurnal variation, and that 

 it differed from the latter only in degree; 

 the ranges in the declination variations, 

 for example, were proportional to the 

 amounts of radiation cut off by the re- 

 spective bodies: the moon and the earth. 



It is known how a moving electrified 

 particle Avill be deflected by a magnetic 

 fleld, and how, in general, it will be made 

 to travel in a spiral path whose axis is the 

 line of magnetic force. Is it possible now, 

 that as a result of the combined action of 

 the permanent magnetic field of the rotat- 

 ing earth and the electrified particles 

 radiated by the sun, there is formed in the 

 regions above us a secondary magnetic sys- 

 tem precisely similar to that of the earth? 



The physical analysis of the permanent 

 field, in addition to furnishing a number of 

 interesting results, thus leads us, in a 

 seductive manner, to the consideration of 

 forces and phenomena not hitherto asso- 

 ciated with those of the permanent mag- 

 netic field. We are led to inquire as to the 

 role played, in the economy of nature, by 

 the magnetic energy stored up in the 

 regions outside, due to the earth's perman- 

 ent magnetic field, in preventing certain 

 solar radiations from reaching the lower 



