On the Great Comet of 1848. 199 
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period that in seven revolutions reaches back nearly to 1689, and 
in eight revolutions to 1668. We now present the argument a 
priort derived from analogy. 
Num- Lon. of Lon. of | Inclina- } Perihelion Perihelion 
ber. Comet. Perihel. Node. tion. distance. | __ passage. 
1 | Comet of 1668 | 279°.6 | 359° .8 | 35° .9 | 0.0048 | Feb. 28.8d 
2 | Comet of 1689 | 273 .5 | 346 .5 | 30 .4 | 0.0103 | Dec. 2.13 
3 | Comet of 1843 | 280 .5| 3848 .5 | 39 .3 | 0.0087 | Feb. 27.54 
4 ze 272 .8 | 356 .5 | 36 .6 | 0.0147 27.20 
5 Se 262 .7 | 357 .7 | 86 .7 | 0.0541 27.55 
6 sf 277 .0| 3861 .8| 35 .7 | 0.0082 27.45 
7 se 274 .8 | 359 .1 | 385 .9 | 0.0109 27.09 
8 ee 274 .5 | 357 .6 | 36 .4 | 0.0113 27.46 
o rs 279 .2| 359 .9 | 36 .0 | 0.0045 27.46 
10 ae 281 .4| 365 .9 | 35 .0 | 0.00380 27.37 
1] te 275 .5| 859 .0 | 36 .1 | 0.0104 27.54 
12 eS 277 .5| 361 .0| 385 .7 | 0.0071 27.47 
13 fe 280 .5 | 364 .6 | 35 .2 | 0.0037 27.39 
14 Ke 278 .£8| 362 22/385 .5| 0.0054 27.41 
1. By Henderson, Astronomer Royal of Scotland. 
2. By Prof. Peirce, from Pingré’s places. 
3. By Prof. Peirce, from his and Mr. Bond’s places. 
4. By Messrs. Nooney and Hadley, from Walker and Ken- 
dall’s places. 
5. By Prof. Anderson, from Prof. Bartlett’s places. 
6. By Prof. Anderson, from Walker and Kendall’s places. 
7. By Prof. Alexander, from his own places. 
8 
. By Mr. Galle of Berlin, do. 
9. By Mr. Plantamour of Geneva, do. 
10. By Prof. Encke, do. 
11. By Walker, Kendall and Downes, do. 
12. By Argelander, do. 
13. By Nicolai, do. 
14. By Laugier and Mauvais, do. 
Hither argument is quite conclusive, and their coincidence es- 
tablishes almost to a demonstration the period of the comet of 21% 
years, and its identity with some of the many others, quoted by 
Pingré in his Cometography, as having occurred in the three se- 
ries of cycles of 175 years (8 revolutions) which precede the re- 
spective dates of its recent appearance in 1843.2, its expected ap- 
pearance in 1864.9 or 1865.0, and in 1886.9. It also completely 
confirms the observation made by Messrs. Herrick and Bradley, 
