258 EF. Loomis— Comparison of Auroral Displays 
2. The excess of the diurnal inequality above six minutes as 
observed at Prague is nearly proportional to the amount of 
spotted surface upon the sun, and may therefore be inferred to 
be produced by this disturbance of the sun’s surface, or both 
disturbances may be ascribed to a common cause. 
The correspondence between the auroral curve and the sun- 
spot curve, though not as close as between the magnetic curve 
and the sun-spot curve, is certainly quite remarkable. The fol- 
lowing table shows the dates of maximum and minimum of 
these two classes of phenomena. Column third shows the dif- 
ference between the dates in the first two columns. 
Date of Maximum, || Date of Minimum. 
Solar Spots.| Auroras. S— A. | Solar Spots.| Auroras, s— A. 
7178 78 0 1784 1784 0 
1788-5 17875 +13°0 1798 1798 0 
804 1 5 —0° 1810 811 —10 
181675 1818 —1'5 1823 823 0 
1829°5 1830 —0°5 1833°5 1834-5 —1°0 
1837 1840 —3°0 1843°5 3 0 
1848°5 1850°5 —2°0 1856 1856 0 
1860 1859°5 +0°5 1867 1867 0 
1870 1870°5 —O0°5 paige ey falas 
In only two cases is there any sensible difference in the dates 
of minimum of the two classes of phenomena. so in the 
year 1810 only one aurora was recorded, so that this year 
presents no real discrepancy in the dates of minimum. 
From 1832 to 1835 the number of auroras was quite small, 
so that for the entire series of observations we may say there 18 
an almost complete identity in the dates of minimum of the 
two classes of phenomena. 
With regard to the dates of maximum there is some discord- 
ance, which in 1840 amounts to three years. It is also notice- 
able that the magnetic curve remained nearly stationary from 
1836 to 1838 while the sun-spot maximum was sharply defined, 
suggesting the idea that the connection between the auroral and 
magnetic curves is more intimate than between the auroral and 
sun-spot curves. 
The discrepancy in 1850 is apparently due to a double or 
leu The New Haven obser- 
in 1848, 1850 and 1852, the greatest frequency being in 1850; 
that is, there was a prolonged period of unusual auroral displays 
extending over several years. 
A comparison of both maxima and minima indicates that the 
critical periods of the auroral curve occur a little later than 
