Fig. 19. Jan. 24, 1836. 



Fig. 21. Jan. 26, 1S36. 



Fig. 20. Jan. '25, 1836. Fig. 22. Jan. 27, 1S36. 



HALLEY'S COMET DEPARTING FROM THE SUN IN 1836. 



COMETS. 



CHAPTEE II. 



24. Why like effects are not manifested in the motion of the planets. 25. 

 Corrected estimate of the mass of Mercury. 26. Biela's comet. 27. Pos- 

 sibility of the collision of Biela's comet with the earth. 28. Resolution 

 of Biela's comet into two. 29. Changes of appearance attending the 

 separation. 30. Faye's comet. 31. Reappearance in 1850-1 calculated 

 by M. Le Verrier. 32. De Vice's comet. 33. Brorsen's comet. 34. 

 D' Arrest's comet. 35. Elliptic comet of 1743. 36. Elliptic comet 

 of 1766. 37. Lexell's comet. 38. Analysis of Laplace applied to 

 Lexell's comet. 39. Its orbit before 1767 and after 1770 calculated 

 by his formulae. 40. Revision of these researches by M. Le Verrier. 

 41. Process by which the identification of periodic comets may be 

 decided. 42. Application of this process by M. Le Verrier to the 

 comets of Faye, Be Vico, and Brorsen, and that of Lexell their 

 diversity proved. 43. Probable identity of De Vico's comet with the 



LARDNER'S MUSEUM OP SCIENCE. M 161 



No. 138. 



