REPORT ON ASTRONOMY. 
163 
was established, and it was observed by Rumker. The ap¬ 
proach to the sun was confirmed by this observation (Berlin 
Ephemeris 1826). Damoiseau however, rejecting the earlier ob¬ 
servations, found in the later ones no proof of resistance ( Conn. 
des Temps 1827) ; and Encke himself (Ast. Nadir. No. 123,) 
acknowledged that the supposition of resistance would not re¬ 
concile all the observations. It was predicted and generally 
observed in 1825 ; and so anxious were astronomers to discover 
it, that two new comets were found in looking for it; but this 
return was not favourable for deciding on the question of re¬ 
sistance. Finally, it was predicted and generally observed in 
1828 and 1829 ; and now at last the point was cleared up. The 
axis of this comet’s orbit lies nearly in the plane of Jupiter’s 
orbit, and its aphelion is very near to Jupiter’s orbit. Con¬ 
sequently, when Jupiter is in that part of his orbit while the 
comet is at aphelion, the perturbations of the comet are ex¬ 
cessive ; and if an erroneous mass is used for Jupiter, its cal¬ 
culated place will be very erroneous. This was nearly the 
situation of Jupiter between the appearances of 1819 and 1822 
(when the perturbation produced by Jupiter in one revolution 
of the comet retarded the perihelion passage nine days) ; and 
the mass assumed for Jupiter by Encke and Damoiseau, in their 
calculations, was that of Laplace. Upon proceeding in the 
equations of condition with a term for the determination of Jupi¬ 
ter’s mass, a value was found very nearly agreeing with that which 
Nicolai had found from the perturbations of Juno, and Encke 
from those of Vesta ; and now with the supposition of a resisting 
medium everything was reconciled. The magnitude of the re¬ 
sistance is such as to diminish the periodic time about xTnrs-o of 
the whole at each revolution; a quantity so large that there 
can be no mistake about its existence. The history of this 
discovery is undoubtedly the most curious that modern astro¬ 
nomy has presented. An abstract is given in the Ast. Nadir. 
No. 210 and 211, and the first part of a longer paper in the 
Berlin Memoirs has lately arrived. The place of this comet is 
predicted for the present year; it must be difficult to observe 
it in Europe, (I know not whether it has yet been seen,) but it 
has probably been observed at the Cape of Good Hope. 
In 1826, M. Biela (a military officer at Prag,) discovered a 
comet which it appears he had partly expected. Calculation 
showed that its path was elliptic, and it was soon found that 
its elements agreed with those of the comet that passed its pe¬ 
rihelion about the first day of 1806, (for which Gauss had found 
a short period.) The elements of a comet of 1772 agreed so 
nearly, that in 1806 Gauss had thought it probable they might 
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