Progress of Astronomy during the Year 1879. 4357 
glass*. Deimos was observed on three nights in November at 
Dunecht, and on one night (November 12th) at Greenwich.t 
Jupiter has attracted a good deal of attention in 1879, especially 
a large oval red spot in the southern hemisphere, which had been 
watched the year before by Tempel, Trouvelot, and others. It 
does not seem to have altered its place in the course of the year, 
the period of rotation resulting from Mr. Pratt’s observations of 
it (9°55™33°-91) being in good accordance with previous results.t 
It was observed spectroscopically by Copeland, who found the 
spot marked by a longitudinal dark band in the spectrum of 
Jupiter, which absorption seemed more restricted to the region 
near b and F when the slit was placed parallel to the belts 
than when it was perpendicular to them.§ 
M. Niesten of Brussels has written a paper in the “ Bulletin de 
l Academie Royale de Bruxelles’ in which he quotes the observation 
of a similar spot by Cassini in 1666, 1672, and 1677, by Maraldi in 
1708-9, by Secchi in 1857 [?], and by Mr. Gledhill in 1871. The 
red colour is, however, not mentioned by these observers. M. 
Niesten suggests, that the phenomenon has a period of five or 
six years, the spot appearing a little before Jupiter comes to his 
perihelium and some time before the aphelium. 
Saturn.—A. Hall finds by applying the equation given by 
Laplace in the Méc. cel. IL, p. 52, for the surface of an ellipsoid 
of revolution composed of a homogeneous fluid, that Saturn like 
Jupiter is less flattened than it would be in case of homogeneous- 
ness, and that the density consequently increases towards the 
centre. The mean density of Saturn being only three-fourth 
that of water, the fluid at the surface must have a very small 
density. 
Mr. Common writes to Nature (XX., p. 577) that the dusky 
ring was seen early in October very prominently. It had the 
appearance of being covered with bright points such as a rough 
dusk paper touched with chalk would give, that part in front of 
the ball being dark, and showing as a fine dark line across, equal 
in width and shade to the shadow beneath, so that the narrow 
part of the whole ring appeared on the face of the planet as if 
bounded by two fine parallel dark lines. 
* M.N., XL., p. 95, and Obs., III., 270. + M.N., XL., pp. 102 and 161. 
{M.N., XL, p.156. §MN., XL, p.88 || A.N. 2269. 
