190 COSMOS. 



(60,126d'7), and the Comet of Encke (3-3 years) with the 

 Comet of 1680 (8814 years), observed by Gottfried Kirch at 

 Coburg, Newton, and Halley. The distance of the fixed star 

 nearest to our solar system (a Centauri) from the aphelion 

 (point of greatest distance from the Sun) of the last-named 

 comet is determined by Encke in an excellent treatise. The 

 small velocity of its motion (ten feet in a second) in this out- 

 ermost part of its orbit, the greatest proximity which the 

 Comet of Lexell and Burckhardt (1770) has attained to the 

 earth (six times the distance of the Moon), and the Comet 

 of 1680 (and still more that of 1843) to the Sun, I have al- 

 ready treated of in. Cosmos, vol. i., p. 109, and vol. iv., p. 

 53-55. The second comet of the year 1819, which ap- 

 peared, in Europe, suddenly to break forth from out of the 

 Sun's rays in considerable magnitude, passed, according to 

 the calculation of its elements, across the Sun's disk on the 

 26th of June ;* unfortunately, its passage was not observed. 

 This must also have been the case with the Comet of 1823, 

 which, besides the ordinary tail turned from the Sun, had 

 also another turned directly toward it. If the tails of both 

 comets had a considerable length, vaporous parts of them 

 must have mixed with our atmosphere, as certainly often hap- 

 pens. The question has been raised as to whether the won- 

 derful mists of 1783 and 1831, which covered a great part of 

 the Continent, %vere consequences of such an admixture ?t 



While the quantity of radiant heat received by the Comets 

 of 1680 and 1843 in such close proximity to the Sun has 

 been compared to the focal temperature of a 32-inch burn- 

 ing mirror,$ a highly-deserving^ astronomical friend of mine 



* Galle, in the Supplement to Olbers's Cometenhahnen, p. 221, No. 

 130. (With respect to the probable passage of the two-tailed comet of 

 1823, see Edinb. Rev., 1848, No. 175, p. 193.) The treatise shortly be- 

 fore quoted in the text, containing the true elements of the Comet of 

 1680, contradicts Halley's fantastic idea, according to which, with a 

 presumed period of 575 years, it had appeared at all the great epochs 

 of the human race: at the time of the Deluge according to Hebrew tra- 

 ditions, in the age of Ogyges according to Greek traditions, at the Tro- 

 jan war, on the destruction of Nineveh, on the death of Julius Caesar, 

 &c. The period of revolution resulting from Encke's calculation is 

 8814 years. The least distance from the surface of the Sun was, on the 

 17th of December, 1680, only 128,000 geographical miles ; consequently, 

 80,000 less than the distance of the Earth from the Moon. The aphe- 

 lion is 853-3 times the distance of the Earth from the Sun, and the 

 proportion of the smallest to the greatest distance from the Sua is as 

 1 : 140,000. t Arago, in the Annuaire for 1832, p. 236-255. 



X Sir John Herschel, Outlines, § 592. 



§ Bernhard von Lindenau, in Schum., Astr. Nachr., No. 698, p. 25- 



