PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. V. 64! 



decisive conclusions can be drawn, but from united observations from the entire globe, and when looked 

 upon in this way the result appears in the present case to be of a decided, positive nature. 



We will first take the astronomical observations among which those of Mr. INNKS, at the Trans- 

 vaal Observatory, are the most fully reported with the definite object in view of discovering whether 

 the forms observed of some part of the comet's tail can be ascribed to the electro-magnetic influence 

 the earth. 



By the 22iid May, Mr. INNES had already sent the following letter to 'Nature': 



The Earth and Comets' Tails. 



"In spite of the unreserved predictions of astronomers, the Earth did not pass through the tail of 

 Ilalley's Comet on the i8th igth May, nor subsequently. The tail as seen in the morning sky, pre- 

 vious to the transit of the comet across the Sun's disc, appeared like a long and straight beam of light 

 stretching from the horizon to Aquila. It was noticed from day to day that the tail was practically 

 fixed irv position in the sky. We rather expected the tail to get nearer to Venus and Saturn as the 

 comet approached the ecliptic, but it remained stationary. On the morning of transit, i8th igth May, 

 the tail was unchanged, but a second branch to the south was now noticed. It joined the northern 

 branch to the east ot the Square of Pegasus. Unfortunately this southern branch was near the zodiacal 

 light and only distinguished from it with difficulty. Both of these tails were seen morning by morning, 

 including this morning (22nd May, civil day), but they have diminished in brightness and were difficult 

 ,to see. further observation of these will be impossible, because of the Moon remaining above the 

 horizon until after dawn during the next ten days. The whole eastern horizon where the tails meet, 

 ami where the zodiacal light is, was suffused with a dim and indefinite glow which was particularly 

 noticeable on the i8th igth and 2oth 2ist. This glow was not so definite in boundary as the 

 zodiacal light. When the comet was seen on the evening of the 2oth, we were surprised to see it had 

 the ordinary tail pointing away from the Sun as usual. It had been noticed for several days that in 

 the neighbourhood of the Sun the sky was not so blue as usual, but this was the case even a week 

 before the transit and is probably merely a meteorological phenomenon. This brief summary of the facts 

 will suffice here; the observations in detail will be published elsewhere. 



"We have now to explain the reason why the Earth did not pass through the tail of the comet 

 and why the tail broke up so that some of it was left in the morning sky, where it remains and is 

 slowly losing its luminosity, and some (or another tail) appeared in the evening sky. It is well known 

 :hat a comet under the Sun's radiant action (I do not attempt to define it more closely) expels cor- 

 juscles towards the Sun, which the Sun repels, and these luminous corpuscles form the tail. This pro- 

 :ess goes on even when (as in the case of Halley's Comet) the distance between the comet and the Sun 

 xi-ceds the distance of the Earth from the Sun. If the nearer planets do not show tails it is because 

 .hese corpuscles have been shed by the planets ages ago. In short, a comet and a planet under the 

 radiant action of the Sun, and the Sun itself, all repel these corpuscles. This being so, it is impossible 

 for the Earth to go through the tail of a comet; it simply repels the tail, and as a consequence, instead 

 >l a passage through it, a disruption near the time of passage must occur, one part being left in the 

 in this case) morning sky, whilst a new one is developed in the evening sky. Here I might remark 

 hat on the evening of the 2oth the measured length of the new tail was 19, on the 2ist 32, and on 

 :he 22nd it was 40. Again, the Earth is bombarded with meteorites which are also throwing off cor- 

 niscles. These will be repelled by both Earth and Sun, so that if we look at the part of the sky 

 opposite to the Sun we should and do see the faint tail thus formed, which is known as the Gegen- 

 ^chein. This simple theory explains all the facts of observation, and if it is correct, will save nervous 

 individuals some worry when the next near approach of a comet's tail is imminent. 



