REPORT ON ASTRONOMY. 
155 
regretted that no measures of the elongations of these satellites 
have been made, as they would throw much light on the mass 
of Jupiter, upon which (as I shall mention hereafter,) there is at 
present considerable doubt. 
The motions of Saturn’s largest satellite have lately attracted 
some attention. In the Berliner Jahrbuch 1814, is a discussion 
of Bessel’s ; from the motion of its apse he concluded the mass 
of Saturn’s ring to be -g-fr that of the planet. In the Zeitschrift 
1817, he predicted a series of conjunctions which it was desira¬ 
ble to observe. In the Ast. Nachr . Nos. 193, 194, 195, and 
214, he gave new investigations (from observation of conjunc¬ 
tions and of the passage of its shadow on Saturn); he con¬ 
cluded the mass of the ring to be -r-hr that of Saturn, and found 
for Saturn’s mass a value agreeing nearly with Bouvard’s. In 
No. 208 of the same work, is a prediction of eclipses by 
Madler. 
On the satellites of Uranus nothing is known except what 
was published by Sir W. Herschel, Phil. Trans. 1815 ; though 
it is understood that his conclusions as to the positions and 
dimensions of their orbits have been verified by Sir John 
Herschel. 
A new method of giving the places of planets has been intro¬ 
duced, principally by Gauss ( Monat. Corr. 1812, and Theoria 
Motus ), namely, of giving the place, referred to the sun, by rect¬ 
angular coordinates, two of which are parallel to the earth’s 
equator. The sun’s place, referred to the earth, being given 
in the same way, the coordinates of the planet referred to the 
earth are found by simple addition, and from these the right 
ascension and declination are found with great ease. This 
method is generally used for comets : in the Astron. Trans. 
vol. 3, Littrow proposed to use it for planets : and Weisse in 
1829 published Tables for all the planets. These Tables admit 
of the introduction of secular change of the elements, but not 
of periodical perturbations: and on this account I think that 
they will now be little received. 
A vast number of observations of planets is to be found in 
the Transactions, the Ephemerides, and the astronomical perio¬ 
dicals. Their object however is generally rather confined. 
The inferior planets are little observed : the superior, little ex¬ 
cept at opposition. At the regular observatories they have 
been much neglected. In the Berliner Jahrbuch 1816, it is re¬ 
marked that in two years there were only six observations of 
planets at Greenwich. The foreign observations are some¬ 
times given without any comparison: sometimes however (es¬ 
pecially in the Milan Ephemeris,) they are compared with the 
