1898-99.] | MAGNETIC INFLUENCE OF SUN ON THE EARTH AND ON COMETS. 355 
Just as the coincidence of auroral phenomena with magnetic storms 
proves their connection, so if changes in the nuclei and the appendages 
of comets are synchronous with magnetic storms and solar outbursts, we 
may regard it as proved that solar outbursts which disturb the magnets 
here reach the comets too, and, in a similar way, whatever it may be.* 
It has not been easy to collect facts bearing on this branch of my sub- 
ject, because astronomers have hitherto had no hint from the magnet- 
ologists to look for and note the precise dates of changes in comets’ 
tails. The next great comet must, however, be most carefully watched 
at every symptom of a magnetic disturbance. Such observations as I 
have gathered together are presented :— 
1. Encke’s Comet, 1871, was globular, but on November gth “ it exhib- 
ited a new aspect, anything but globular.” 
On that day the principal depression of the month occurred, though 
not an important one. 
2. Coggia’s Comet, 1874, had a tail which “became exaggerated” on 
July 13th. There was a noticeable depression on that day. 
3. Brooke’s Comet of 1883 showed nothing remarkable until October 
22nd, when a photograph disclosed the fact that it was broken up into 
Thus, he places April 17th in both the latter categories. which is manifestly wrong. It should be ruled 
out of both. 
The remaining two cases in No. 3 are July 1st and September 27th. Now, on July ist, a magnetic dip 
does begin, and continues until the grd. On September 27th there is a dip also. In both cases the depressions 
are only sufficient to produce local aurorz, and as his own tables show that there were many aurorz in the 
United States on these dates, though there were none observed in Sweden or Norway, and only one in 
Russia, the rule is followed, but the dates should not be giyen in the list of aurorze of a general nature, 
The dates given in Category No, 2 are March 1st, July 2oth, September r4th and tgth, and No- 
vember 13th. 
The magnetic depression of March ist is part of the storm of February 2rst to 26th, not nearly so severe, 
and the tables given by Father Lais show an almost exact concordance between the intensity of the magnetic 
storm and the frequency of aurorz observed, including March istand 2nd, especially when we add the Cana. 
dian record. 
The figures for July 15th to 24th, in the Washington Weather Review are: 
WAY Sore che vistas ste a eee ward eminae aoe ee 15 16 17 18 19 20 21 22 23 24 
ING rece. fo nonin eiciaareriarsas ° ° ° 2 2 5 3 I I I 
ae as rin (Or ai NOB ee seo bonane 2 5 3 o 5 7 I I 4 I 
The aurorz observed were tew, the moon being full, but by far the greatest number corresponds with the 
day of the dip. 
In September the figures are: 
IDE ERaauia Hacc acosonede ED LIZ, CAL XG AO AGS is creiices srecslcoiee eee 17 318° 49)-- 20 ar 
No. of Auror2 .......... On 0-43 V4 Gro No: of Anrorcey.ch- erase Oo 13 «#27 Seal 
se ss in Canada. r6 42 .go.+38 oa as —ineGanadas\ gy) 8) 28. -. 3. «46 
There was a full moon at the earlier dates also, but again the increase in number agrees with the day of 
the dip. The magnetic disturbance of November 13th gave rise to aurore toa. It was a bright, full moon, 
but there were none seen from the 7th to the 13th, when there were 8, and none the next day after. 
*Dr. Veeder thinks that planetary space is so full of particles of matter that electrical force is trans- 
mitted from sun to earth by continuous induction. 
