DEPARTMENT OF TERRESTRIAL MAGNETISM. 261 



complete observations for determining the changes in magnetic declination 

 and horizontal intensity were made. With a view of varying the conditions, 

 the station selected by L. A. Bauer for his work was at Corona, Colorado, 

 the elevation of which was 11,800 feet; the changes in magnetic declination 

 observed during the eclipse at this mountain station proved to be of special 

 interest. 



The various curves based on the results of the magnetic observations at 

 the different stations, especially in the zone of visibility, show a number of 

 interesting features. For several days prior to the day of the eclipse, sun-spot 

 activity was very pronounced; while on June 8 there were still some spots 

 visible, they were near the sun's western edge and at stations in moderate 

 latitudes apparently did not cause magnetic disturbances, such as occur 

 during the time of a cosmic magnetic storm. The conditions for observing 

 the minute magnetic effects to be associated with the solar eclipse were 

 therefore favorable, and the various curves clearly indicate that such effects 

 were observed. It is pointed out that, in general, the most notable effects 

 revealed by the magnetic curves did not occur according to absolute time 

 nor according to local mean time, but followed closely the times at which the 

 echpse occurred at the different stations. The stations in the United States 

 also revealed magnetic effects before the time of the local eclipse resulting 

 evidently from the easterly progression of the effects which had arisen in 

 the portion of the earth over which the eclipse had already occurred. 



Not only were the conclusions reached with reference to the echpse of May 

 28, 1900, and subsequent echpses, verified by the effects observed during 

 the eclipse of June 8, 1918, but a number of additional facts have been disclosed 

 which will assist materially in the final analysis of this interesting phenome- 

 non. It was again shown that the magnetic fluctuations observed during 

 the eclipse are analogous in their nature to the solar diurnal variation, differing 

 from it only in degree. Retardations and interruptions in the usual curves 

 of the diurnal variation, as found during the previous eclipses since 1900, 

 were again distinctly evident in the magnetic curves applying to the echpse 

 under discussion. 



The average range in the fluctuations of the horizontal intensity was about 

 0.03 per cent, in the vertical intensity about 0.02 per cent. The average 

 range of the fluctuations in the magnetic declination varied from 1 to 2 

 minutes of arc. 



An approximate estimate of the magnitude of the effect as shown by the 

 observed changes in horizontal intensity and vertical intensity is that the 

 effect was about equivalent to that associated by the first author with a ten 

 per cent change in the solar radiation, as indicated by the values of the 

 solar constant observed under the auspices of the Smithsonian Institution. 



Brief reference is made to the various causes which might be responsible 

 for the observed magnetic effects during an eclipse and how it wouM be pos- 

 sible, upon the basis of the accumulated data, to make a test of the various 

 hypotheses. 



Preliminary results of ocean magnetic observations on the Carnegie from Buenos Aires 

 to Talcahuano, Dec. 1917-Jan. 1918. H. M. W. Edmonds. Terr. Mag., 

 vol. 23, 23-24 (Mar. 1918). Washington. 



Preliminary results of ocean magnetic observations on the Carnegie from Talcahuano to 

 Balboa, Jan.-April 1918. H. M. W. Edmonds. Terr. Mag., vol. 23, 69-72 

 (June 1918). Washington. 



Preliminary results of ocean magnetic observations on the Carnegie from Balboa to 

 Washington, D. C, April- June 1918. H. M. W. Edmonds. Terr. Mag., vol. 

 23, 139-140 (Sept. 1918). Washington. 



