COMETS. 95 



by Arago and myself, at the Observatory at Paris, to assume 

 very different forms ( 45 ) on successive nights. The great 

 Konigsberg astronomer concluded from many measure- 

 ments and from theoretical considerations, " that the out- 

 streaming cone of light deviated notably both to the 

 right and to the left of the true direction towards the 

 sun, but that it always returned to that direction, and passed 

 beyond it to the opposite side ; so that both the cone of light, 

 and the body of the comet from which it issued, were subject 

 to a rotatory, or rather vibratory motion, in the plane of the 

 orbit." He finds " that the ordinary power of the attractive 

 force of the sun on gravitating bodies is not sufficient to explain 

 such vibrations, and is of opinion that they would seem to 

 indicate a polar force, which tends to turn one of the semi- 

 diameters of the comet towards the sun, and the opposite 

 semi-diameter from the sun. The magnetic polarity possessed 

 by the earth may present something analogous, and should 

 the sun have the opposite polarity, a resulting influence 

 might manifest itself in the precession of the equinoxes." 

 This is not the place for entering more at length into this 

 subject : but observations so remarkable, and so important 

 with reference to the most wonderful class of cosmical bodies 

 belonging to our solar system, ought not to be entirely 

 passed over in this general view of nature ( 46 ) . 



Although, in the greater number of cases, the tails of 

 comets increase in magnitude and brilliancy in the vicinity 

 of the sun, and are directed from that body ; yet the comet 

 of 1823 offered the remarkable example of two tails, one 

 turned from and the other nearly towards the sun, forming 

 with each other an angle of 160. Peculiar modifications of 

 polarity, and its unequal distribution and conduction., may in 



VOL. I. I 



