324 Remarks on the Tails of Halley's Comet. 



Art. XX. — Additional Remarks on the Tails of Halley's Comet; 

 by Prof. B. F. Joslin. 



Having just seen, for the first time, an article on Halley's Comet 

 by the distinguished French philosopher, M. Arago, I am induced 

 to make some quotations, and some additional remarks suggested by 

 a comparison of observations. 



The paper on the tails of Halley's Comet was read before the 

 astronomical class in Union College, in February, 1836. I was af- 

 terwards gratified to find, in a number of the American Journal pre- 

 viously published,* a notice of the brush of light seen October 12th 

 at Yale College. The observation here of the 12th of October 

 was noticed in the Schenectady Reflector of the 14th. Whilst the 

 paper on the tails of Halley's Comet was in the press, Mr. E. C, 

 Herrick politely furnished me with some French extracts from a pa- 

 per on this comet written by M. Arago, for the Annuaire for 1836, 

 published by the Bureau des Longitudes. It appears that a similar 

 brush, sector, or tail, (and sometimes more than one,) was seen in 

 Europe and excited much interest : — length estimated at not less than 

 two hundred thousand leagues, yet comprehended (like that seen 

 here) within the fainter nebulosity. It appears to have been seen 

 in the United States earlier than in any part of Europe, so far as the 

 observations are given in the Annuaire. It was seen at Paris on the 

 15th, 16th, 17th and 18th of October; at Schenectady as a well de- 

 fined tail with divergent sides, (or, as I have frequently called it, a 

 sector, a term which M. Arago also employed,) on the 12th, 13th, 

 16th and 17th, as many evenings as at Paris. Whilst on the 1 4th, 

 I have referred to the same thing seen more indistinctly, viz. such 

 an increase in the density or luminousness in the interior of the en- 

 velope on one side of the nucleus as to render it visible in a state of 

 the atmosphere when the envelope could not be seen with the tele- 

 scope at the same distance in other directions. But in both cases I 

 have with others regarded it as comprehended within the envelope, 

 and as being a tail only to the nucleus. It appears from the Annu- 

 aire, that M. Schwabe, a German astronomer, in a memoir presented 

 to the Academy of Sciences, has used a similar term, calling the 

 luminous sectors, opposite to the tail properly so called, " secondary 



* Vol. XXIX, No. 1, p, 156, October, 1835. 



