COMETS. 



apparent brightness was so much increased, that at the latter date 

 it was visible to the naked eye as a star of the 6th magnitude. 

 The apparent diameter was then reduced to 9'. 



On November 7th a star of the llth magnitude was seen 

 through the comet, so near the centre of brightness that it was 

 for a moment mistakeif for a nucleus. The brightness of the 

 star was not in the least perceptible degree dimmed by the mass 

 of cometary matter through which its light passed. 



It was evident that the increase of the brightness of the comet 

 on the 30th November, must be ascribed to the contraction, and 

 consequent condensation, of the nebulous matter composing it 

 in receding from the sun, for its distance from the earth on the 

 7th November, when it subtended an angle of 18', was 0-515 (the 

 earth's mean distance from the sun being =1) ; while its distance 

 on the 30th, when it subtended an angle of 9', was only 0'477. 

 Its cubical dimensions must, therefore, have been diminished, 

 and the density of the matter composing it augmented in more 

 than eight-fold proportion. 



87. The expectation so generally entertained, that, on the 

 occasion of its return to perihelion in 1835, this comet would 

 afford observers occasion for obtaining new data, for the 

 foundation of some satisfactory views respecting the physical 

 constitution of the class of which it is so striking an example, 

 was not disappointed. It no sooner reappeared than phenomena 

 began to be manifested, preceding and accompanying the gradual 

 formation of the tail, the observation of which has been most 

 justly regarded as forming a memorable epoch in astronomical 

 history. 



Happily, these strange and important appearances were 

 observed with the greatest zeal, and delineated with the most 

 elaborate and scrupulous fidelity by several eminent astronomers 

 in both hemispheres. MM. Bessel at Konigsburg, Schwabe at 

 Dessau, and Struve at Pultowa, and Sir J. Herschel and Mr. 

 Maclear at the Cape of Good Hope, have severally published their 

 observations, accompanied by numerous drawings, exhibiting 

 the successive transformations presented under the physical 

 influence of varying temperature, in its approach to and departure 

 from the sun. 



The comet first became visible as a small round nebula, without 

 a tail, and having a bright point more intensely luminous than 

 the rest eccentrically placed within it. On the 2nd October, the 

 tail began to be formed, and, increasing rapidly, acquired a length 

 of about 5 on the 5th ; on the 20th it attained its greatest length, 

 which was 20. It began after that day to decrease, and its 

 diminution was so rapid, that on the 29th it was reduced to 3, 

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