360

THE PLANET SATURN.

sion the appearances shown in Fig . LXXXIII. during theabove-mentioned period.

Twice in the 29J years, as in February 1878 and October1891, they would be looked at edgewise, and would be reduced,as we have stated, to a very fine line, or for a few hours be in-visible. Twice, as at the beginning of 1885 and in the middleof 1899, they would be seen in their most fully opened appear-ance, when they would, however, still fall short of a circular

Fig. LXXXIV.—The plane of Saturn’s rings sweeps across the Earth ’s orbit, ee,e 2 e 3 ,while Saturn is travelling from c to d. When Saturn is at a the plane of the ringspasses through the Sun.

contour, the greatest ratio of the minor to the major axis oftheir apparent form being as 45 to 100. It is also to be noticed,as is shown in the figure, that during one-half of the time,or for about 14f years, the Sun would illuminate the northernsurface of the rings; and during the other half of the timetheir southern side.

The view of the rings obtained by an observer upon the Earth does not in general differ much from that which would be seenfrom the Sun. Some slight allowance must be made for thefact that the Earth ’s plane of motion round the Sun (or, inother words, the ecliptic) is slightly different from the plane