CONTRIBUTION TO THE KNOWLEDGE OF THE 
INFLUENCE OF SOLAR ECLIPSES ON 
TERRESTRIAL MAGNETISM 
BY 
Dr. W. VAN BEMMELEN. 
The magnetic observations performed under the supervision 
of Dr. L. A. Bauer of Washington on the day of the total 
solar eclipse of May oer. 1900 in the United States have 
made evident the existence of a slight effect of a solar eclipse 
on the magnetic needle. 
The results of international coöperation during the eclipse 
of May 18%, 1901 have confirmed the reality of this effect 
and BAUER, giving a résumé of the output of a systematic 
treatment of the whole material of observations, concludes !): 
„the establishment of the facts that an observable magnetic variation 
„makes itself felt during the time of a solar eclipse, and that 
„this variation is analogous in its nature to the solar-diurnal 
„variation, differing from it only in degree.” 
This conclusion is drawn from the result, that 2): „the 
„Precise effect of the eclipse magnetic variation is: (1) opposite for 
„the two magnetic hemispheres > (2) opposite for the morning and 
„afternoon hours”; and this result is founded on the effects, 
observed at different stations summarised in the following 
table. 3) 
1) Terrestrial Magnetism, Vol. 7, p. 192, 
7 » " Vol. 7, p. 189. 
» - " Vol. 7, p. 189. 
