Astronomical and Nautical Collections. 87 
No. Year. 
19. 1558. From three observations of the Landgrave of Hesse, and one of 
¢ Cornelius Gemma, the latter being corrected in what is, very 
probably, an error of the press. Gemma de Nature Divinis 
Characterismis. Book II. ch. i. p. 33. See Berl. Astr. Jahrb. 
1817, p. 176. 
20. 1577. From Tycho’s Observations. Pingré I. p, 511. 
21. 1580. Halley from Méstlin, Pingré from Tycho’s better obscrvations. 
Pingré L. p, 521. 
22. 1582, Both orbits uncertain, since they are founded only on three 
observations of Tycho, of the 13th, 17th, and 18th of May ; 
that of the 18th giving a double result, whence the two orbits 
are derived. The first elements seem the most probable, 
Pingré I. p. 544. 
23, 1585. From the observations of Tycho and Rothmann. Pingré I. 
. 550. 
24, 1590. Tycho’ observations, from 23 February to 6 March. Pingré 
. p. 554. 
25. 1593. Bocrlat to the observations of Chr. J. Ripensis, at Zerbst. 
Mem. Par. 1747, p. 562. Pingré I. p. 557. 
26. 1596. Halley from Méstlin, Pingré from Tycho’s observations : hence 
the latter elements are preferable. Pingré L. p. 562. 
(15) 1607. Halley’s comet. Pingré [I. p. 3. Halley's Tab. Astr. First 
supplement of the Berl. Astr. Jahrb. Mon. Corr, X. p. 425. 
27. 1618. From Kepler's imperfect observations. Kepler de Cometis. 
Pingré II. p. 4. 
28. 1615. Bessel’s orbit is far the best, being founded on the observations 
- of Harriot, Longomontanus, Cysat, and Schnellius. Berl. 
Astr. Jahrb. 1808, p. 113. 
29. 1652. From the observations of Hevelius between the 20th December 
and the 8th January. Hevelius’s observations are not only 
in the second volume of the Machina Celestis, which is very 
rare, but also in his Cometographia, 
30. 1661. The observations of Hevelius from the 3d February to the 28th 
March. Machina Ceelestis [., and Cometographia. Mém. 
pres X. p. 350. 
81. 1664, Hevelius'’s observations in the Prodromas Cometicus, or better 
in the Mantissa Prodromi, and in the Machina Cel. II, p. 
439. Pingré LI. p. 10. 
32. 1665. From Hevelius's observations from the 6th to the 20th April, 
which are found in the Deser. Comet. 1665, Mantissa Prodr. 
Com. and Mach. Ceelestis IL. 
33. 1672. According to Hevelius’s observations from the 6th March to 
the 21st April. Mach. Cel. IL. p. 593. 
34. 1677. According to Hevelius’s observations from the 29th April to the 
8th May. Flamstead observed it also twice. Mach. Col. IL. 
p- 292, Flamstead Hist. Cel, Br. Ed, 1712, p. 103. Ed. 
1725. I. p. 103. 
35. 1678, From Lahire’s observations, which are only estimated, and from 
the chart in the Hist. Cél. of Lemonnier, p. 238. See particu- 
larly Struyck, 1753, p. 88, 39. 
36. 1680, Euler's elliptical elements are to be considered merely as an 
example of calculation, and require no further consideration. 
It is only the elliptical orbit of Encke that is of any value at 
present ; itis taken from his masterly prize essay on this comet 
