166 EF. Loomis on Solar Spots, Maynetic Declination, ete. 
inequality is so marked as to assume the form of a distinct sec- 
ondary maximum. uch maxima occurred in 1774, 1792, 
1794 (if this is not to be regarded as a primary maximum) and 
1864 ; and in several other cases the inequality in the progress 
from a maximum to the succeeding minimum is decided. The 
mean daily range of the magnetic declination exhibits also sec- 
ondary maxima, and generally the small inequalities in the 
eurve of magnetic declination bear some correspondence to 
the small inequalities in the curve of the solar spots. The au- 
roral curve shows still greater irregularities, and it is kabl 
. that an irregularity in the auroral curve often has a decided 
maximum in 1774; also in passing from the maximum of 1778 
to the following minimum the undulations of the three curves 
bear a marke “resemblance ; in the descent from the maximum 
of 1787, there is a secondary maximum of the netic curve 
corresponding to that of the solar-spot curve; in the descent 
from the maximum of 1848 there are correspon undu- 
lations of the sun-spot curve and the magnetic eurve, while 
the auroral curve shows at the same time a well-marked sec- 
ondary maximum ; sad: nearly the same remark is applicable 
to the descent from the e principal maximum of 1860. 
The following ee are thought to be warranted by 
the preceding observ: 
1. Within the zone eee greatest auroral frequency, auroras ar 
. almost daily occurrence in all years, and it is doubtful whathér 
n this region there is any decided periodicity in the number of 
pas displays, although there may be periodical changes of 
brillianey. 
2. At t places where the average number of auroras is about 
20 or 25 annually, the ten-yearly period of the solar spots can 
be distinctly traced. 
3 e times of maximum and minimum of the solar spots 
correspond in a remarkable manner with the times of maximum 
nin in the frequency of auroral ex anak in the mid- 
e latit 
able than thous of the solar sci so that the ten-yearl pe 
riod might be easily overlooked, and it might be ish that 
similar though generally smaller inequalities in the ae of so- 
lar bance or of magnetic declination. 
