THE PLANET SATURN.

391

we did in the case of those of Jupiter . Of course such eclipsesoccur upon portions of the surface of the planet from time totime, but the shadows of the satellites when they are in thephase of new moon will much more often than not miss itsdisc, owing to the considerable tilt of their orbits to the planeof Saturn ’s path. If such an eclipse is occurring, sufficienttelescopic power ought no doubt to show the shadow to us,as a small dark spot, travelling across the disc, similar to thosewhich we so often see upon Jupiter . And it is very interestingto know that, in the case of Titan, this phenomenon mayoccasionally, although rarely, be observed. It was once seen

Fig . LXXXIX.—Saturn, December 9tb, 1877, 6h. 4.5m. p.m. Transit of the shadow

of Titan.

by Sir W. Herschel in 1789, by Gruithuisen in 1833, in1862 by Dawes and others, and again on November 7th and'December 9th, 1877. Also on Christmas Day , 1877, by LordLindsay at Dun Echt (see Monthly Notices, Royal AstronomicalSociety , vol. xxxviii., p. 100), and by the writer of this lecture,who made a drawing at the time which agreed very closelywith the more accurate observations taken at Dun Echt.* Thetransit of December 9th, 1877, as seen with an 8£ in. Browningreflector, by Mr. J. Rand Capron, is shown in Fig . LXXXIX. f

* It is also worthy of mention that upon one occasion, viz., in 1692, astar was seen by Cassini to be occulted by Titan; and that in 1862 Dawessaw an eclipse of Titan by its immersion in shadow of Saturn .

t This interesting sketch is extracted, by the kind permission of theAstronomer Royal, from The Observatory, vol. i., p. 289.