On the Formation of the Tails of Comets. 113 



however, should be made for the light intercepted by the atmos- 

 phere, which was the greatest at the lowest of the two points 

 considered. It is believed that doubling the ratio just found will 

 suffice for this. This being done we obtain for the actual ratio, 

 1 to 8, which corresponds very nearly with the ratio computed 

 on the supposition of the existence of an uniformity in the abso- 

 lute quantity of matter. The observations of the 28th of Febru- 

 ary, seem also to ~be in accordance with this supposition. The 

 comet was seen on that day in the immediate vicinity of this 

 place by a very intelligent individual, who informs me that the 

 head was a little smaller than the sun, (certainly not larger,) and 

 that the tail was as much as three times broader, at its extremity, 

 than at the head. The whole comet is described as being simi- 

 lar in form to an ox-bow or the letter U, only that the branches 

 were more divergent — the sky appearing even darker between 

 them than any where else. The observations at Woodstock, Vt., 

 make the variation of breadth a little greater, if we assume the 

 size of the head to have been only £°. It must certainly have 

 been less than 1°, as there was a very marked divergence in the 

 sides of the tail, and the average breadth was not estimated by 

 any of the observers higher than 1°. Agreeably to our supposi- 

 tion, therefore, there must have been a decrease of light, from 

 one end of the comet to the other, in the ratio of 3 to 1 ; and, if 

 we conceive the light to be derived from the sun, it will become 

 as 12 to 1 — which is about the ratio of the quantity of light given 

 by a star of the third, and one of the fifth magnitude, or by stars 

 respectively of the first magnitude and intermediate between the 

 third and fourth. It is moreover quite as great as the observa- 

 tions themselves would seem to warrant us in supposing.* 



* The phenomena of the disappearance of the great comet of 1843, as seen in 

 the vicinity of this place (Newark, Del.) on Feb. 28th, are not a little curious. 

 The comet was first noticed at from 9J to 10 A. M. After having remained visible 

 for about three quarters of an hour, during the latter half-hour of which interval it 

 was almost constantly watched by my informant, in a situation in which the eye 

 was completely protected from the sun, it suddenly began to disappear at the ex- 

 treme points, without there being any perceptible haziness in the atmosphere. 

 The branches continued to shorten, and in a few minutes were entirely wanting. 

 The comet had now assumed the appearance of a round ball, and glowed with a 

 more intense lustre than before. This latter fact is particularly insisted on. This 

 round ball gradually contracted until it became a mere bright point, and then dis- 

 appeared — producing the impression that it was moving away into the depths of 

 space. These facts, as well as those mentioned in the context, came accidentally 



Vol. xlvi, No. 1— Oct.-Dec. 1843. 15 



