FE. Loomis on Solar Spots, Magnetic Declination, etc. 169 
marked maximum on the day of the magnetic storm; a second 
maximum four days before the storm, which is also pretty dis- 
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tinctly marked; and a third maximum, more uncertain, three 
days after the storm. The entire fluctuation within a period of 
two days is from 45:1 to 57-9, or 28 per cent of the smaller 
quantity, an effect which is so large and derived from a com- 
rison of so many cases as to indicate a law of nature. Hence 
we seem authorized to conclude Se 
. Great disturbances of the earth’s magnetism are accompa- 
nied by unusual disturbances of the sun’s surface on the very 
day of the magnetic storm; and are, therefore, due to some in- 
fluence which emanates immediately from the sun 
2 e great disturbance of the sun’s surface which accom- 
panies a terrestrial magnetic storm, is generally heralded by a 
smaller disturbance three or four days previous, succeeded by a 
comparative calm which immediately precedes the magnetic 
storm. 
cases for the purpose of confirming a preconceived theory, I 
have taken the entire series of observations made by Messrs. 
Herrick and Bradley at New Haven, from 1887 to 1854. These 
observations are 514 in number, and I have employed them all 
with the following exceptions : 
Jour. Sci.—SeconD Series, Vor. L, No, 149.—Sepr., 1870. 
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