930 REPORTS FROM THE SECTIONS. 
Note on the Planet Uranus. 
By Joun Tespurt, F.R.A.S. 
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sideration of the eccentricity of the planet's orbit that the oppo- 
sition-distance varies according to the distance of the planet itself 
from its perihelion. Without regarding the small variation due 
to the earth’s distance from its own perihelion, it is also obvious 
that when the opposition takes place at the same time that the 
planet is in or very close to its perihelion the opposition-distance 
is at a minimum, and this is the most favourable opportunity for 
the telescopic sauhasl on of the planet and its satellites. 
combination of circumstances will soon take place ; the planet 
has, in fact, for the past forty years been gradually approaching 
the earth at each successive opposition. It will be remembered 
that in the newspapers I pointed out a somewhat similar circum- 
stance in connection with the planet Mars previously to its oppo- 
sition last year. The heliocentric jones of Uranus at the last 
opposition (15 February, 187 8) v was 147° 5’, and that of the peri- 
helion, according to Chambers’s Descriptive a Aarons, 1885 p. 38, 
is 167° 30’, and as the heliocentric motion of the planet is at pre- 
sent about 43 degrees during a synodical period, it follows that the 
opposition of March, 1882, will fall the nearest to the perihelion 
during the present centu ury. Adopting the peat orbit eleeni nts 
in Chambers s Astronomy, I get 18-2875 and 20-0780 pk eh 
as the perihelion and aphelion distances asec of th 
earth’s mean distance from the sun. The cae ga of the 
earth corresponding to the heliocentric longitudes of the planet’s 
perihelion and aphelion are respectively 0-9932 and 1:0064. From 
these values I deduce therefore 17-2943 and 19-0716 as the mini- 
mum and maximum limits of the variation of the planet’s opposi- 
tion-distance. If now we assume Sir G. B. Airy’s s determination 
(R.ALS. Monthly Notices, Vol. XXXVIII. p. 16) of the sun’s 
mean distance from the telescopic observations of the British Ex- 
pedition for the Observation of the transit of Venus, 1874, me 
eset 000 miles, we have for the real minimum and maxim 
tion-distances 1,615 and 1,781 millions of miles renpentively, : 
2 
