Memoir on the approaching Return of Hallet/s Comet, 51 



drawings in the latter work are very inaccurate, as they had 

 only been roughly sketched by Hooke for the purpose of aid- 

 ing his memory, and were finished by Richard Waller, from 

 Hooke's description (P. Works, p. 164-); yet they illustrate 

 what appears extraordinary in Hevel's drawing, and show 

 that the nucleus of this comet, besides the usual nebulous 

 envelope, was inclosed within a hollow parabolic conoid of 

 bright matter of the same nature as the tail, resembling in some 

 measure, it would seem, the comet of 1811. The nucleus, how- 

 ever, in Halley's comet was ir> immediate contact with the apex 

 of the conoid ; whereas, in the comet of 1811, the apex of the 

 conoid was separated from the nucleus by a dark interval of 

 considerable extent. What Hevel represents as a horn proceed- 

 ing from the nucleus, was merely the northern border of the 

 conoid, which, according to Hooke, is very much brighter 

 than the southern. It is to be expected that on its approach- 

 ing return astronomers will bestow all possible attention on 

 the remarkable peculiarities of form which it will probably 

 only exhibit after the perihelion, and on the changes of appear- 

 ances it undergoes. In the drawing made by Tobias Mayer, 

 on the margin of his Journal, 30th of April 1759, (" Astro- 

 nomical Observations made at Gottingen, from 1756 to 1761, 

 &c., London 1826, fol. p. 43.") no indication is given of this 

 bright conoid, which, 48 days after the comet's nearest ap- 

 proach to the sun, had entirely disappeared. 



Although the comet, on this occasion, will not exhibit any 

 extraordinary splendour, yet the circumstances of its return 

 will be favourable to science, as it will be possible to see and 

 observe it during a considerable length of time. In the 

 southern hemisphere of our earth, where, thanks to Great 

 Britain, several observatories have been erected, and compe- 

 tent astronomers established, the comet will be seen on ex- 

 tricating itself from the sun's rays, after the perihelion pass- 

 age, from about the end of December 1835, till the spring of 

 1836. In the North of Europe, indeed, on account of its con- 

 tinual low altitude above the horizon, it will come less into 

 view; and when in the months of March and April 1836, it 

 has attained to a greater height in the constellations of the 

 Crow and the Cup, it will be at so great a distance from the 

 sun and the earth, that it will appear only as a feeble nebula 

 in the most powerful telescopes. 



While engaged in writing out the last part of this short 

 memoir, I was equally honoured and gratified by receiving 

 an entirely unexpected visit from Professor Rosenberger. 

 Professor Rosenberger is also fully convinced that it is not 



H2 



