SCIENTIFIC SUMMARY. 
175 
making it systematically larger than others. Thus Mr. Ellis’s personal equa- 
tion amounted to + 1"T0, whereas Mr. Dunkin’s was - 0"’68, so that Mr. Ellis 
systematically makes the diameter of Mars 1 "’78 larger than Mr. Dunkin. A 
further result was also ascertained, namely, that the diameter was systemati- 
cally made too large when the planet is at a considerable distance from the 
Earth. Lastly, Mr. Stone considers that the large irradiation constant obtained 
by Mr. Downing is fictitious to a certain extent, and due to other causes. 
1 The Diameter of Vesta. — Last year, from a numerous set of measures, Prof. 
Tacchini of Rome determined the apparent diameter of this minor planet to be — 
= l"-706 ± 0"-09. 
Since then another set of measures has been obtained by his colleague, Prof. 
Millosevich, who finds the diameter to be — 
= 1 "-655 ± 0"-09. 
These results, freed from the effect of irradiation, would give about 800 
miles for the diameter of this planet. 
Jupiter. — Further interesting observations have been made by different 
observers of the changes which are taking place in the cloud strata of this 
giant planet. The white spots on the equatorial belt continue to remain 
visible, but are becoming more irregular in form and dimensions ; their edges, 
too, are becoming softer and less sharply defined. They continue to move 
much faster than the great red spot, which still continues visible, but has 
lost much of the vividness of its tint ; and Mr. Denning has watched one gain 
a whole revolution of the planet on the red spot. The band of dark irregular 
spots on the northern equatorial belt continued to be visible during the winter, 
but they have changed very considerably in form and appearance, rendering 
it difficult to accurately determine the period of their rotation. They seem 
now to move faster than the white spots, though originally Schmidt and 
some other observers considered their motion to be slower. The greyish 
belt north of this belt of blackish spots has grown thicker and darker of 
late, and still further north there are signs of a new belt. Mr. W. F. Denning 
thus sums up the results of his winter observations ( Observatory , March 1881) : 
‘ It is to be noted that the recent observations of this planet have re- 
vealed, in the clearest manner possible, a quadruple series of spot-motions. 
There is the red spot with its period of 9 h 55 m 34 s ; the short, dusky streaks 
(south on the red spot in the southern hemisphere) with their approximate 
line of 9 h 55 j m , the bright spots on the equator with 9 h 50 j m , and the dark, 
irregular spots ranged along the belt north of the equator with 9 h 48 m . 
Further observations may reveal other phenomena of equal importance ; and 
it is certain that the time has come when this planet will be subject to the 
constant and critical examination which the marvellous variations in his 
appearance so obviously demand.’ 
M. Bredichin is of the opinion that all the recent phenomena presented by 
the planet Jupiter can be explained by supposing that there is an elevated 
equatorial belt to the planet, and that there is more heat radiated from the 
southern hemisphere of the planet than from the northern. 
Lately an interesting investigation has been published by Herr Harzer, 
giving the results of his investigation of the perturbing action of this giant 
planet, Jupiter , on the motion of Brorsen’s comet of 1846, on the occasion of 
the very close approach of the comet to Jupiter in May 1842. Herr Harzer 
