92 



THOUGHTS ON THE INFLUENCE OF ETTTER 



After passing through, and out of the downward current, we should expect to see the 

 new tail separate from the head, and another appendage restored in the normal direction. 



On examining the catalogue of comets in Mr. Hind's " Descriptive Treatise," I find in 

 the present century only four, the inclination of whose orhits was more than seventy de- 

 grees, and whose perihelion distance was less than one-fourth of the radius of the earth's 

 orbit. 



Of these four comets, it is recorded of three that they had double tails. 



The first is that of 1823, the inclination of whose orbit was 76° 11' 57", and whose peri- 

 helion distance was 0.22650. The following interesting account of its remarkable appear- 

 ance is furnished by M. Arago. 



"The comet of 1823 (No. 140 of the catalogue) had two tails, and, strange, while one, 

 as is usual, was pointed away from the sun, the other was turned towards that luminary, 

 which gave it a resemblance to the nebula in Andromeda." 



"On the 23d January, 1824, the ordinary tail seemed to be 5° long, the length of the 



to the naked eye, or in a low magnifying telescope, and that only when the comet itself had begun to fade away 

 by reason of its increasing distance." (Herschers Outlines, chapter xi.) 



Okiiit of Hallky's Com ist. 



ABCD, The earth's orbit. 

 E F G, The comet's orbit. 

 H, The sun. 



Inclination, 17° 45' 5". 

 Perihelion distance, 0.58657. 

 Longitude of perihelion, 304° 31' 32". 

 Longitude of ascending node, 55° 9' 59''. 



Orbit of tub Comet of 182:'. 



ABCD, The earth's orbit. 

 E D F, The comet's orbit. 

 H, The sun. 



Inclination, 76° 11' 57". 

 Perihelion distance, 0.22C50. 

 Longitude of perihelion, 274° 34' 30'". 

 Longitude of ascending node, 303° 3' 0". 



