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 took place on midwinter day, while the lowest altitude would be reached in an opposition on Midsummer Day. It is true that the ideally perfect opposition was not reached in 1892. The opposition took place in October, that is to say, two months before the most suitable time. But on the whole the conditions were unusually favourable.

Professor E. E. Barnard had already obtained deserved fame as a skilful astronomical observer, and therefore it is that his announcement of this new discovery has been at once accepted by astronomers. It is the extreme minuteness of the body which is the cause of its having hitherto escaped notice. We are told that the fifth satellite appears as a star of the thirteenth magnitude, if not even very much less. An object possessing no greater brilliance than is thus indicated can only be perceived by a good telescope under the most favourable circumstances. When, however, the difficulties of seeing the satellite are enhanced by the fact that it is located close to so brilliant a globe as the great planet, then it is only the exceptional powers of the Lick telescope, and the exceptional excellence of the situation in which the telescope is placed, which have enabled it to be detected at all. So far as we can estimate the lustre of the new satellite, it can hardly be the five-hundredth part of the lustre of even the faintest of its older companions in the same system. Indeed not improbably the proportion must be expressed by a figure considerably greater than that which I have written. If one of the older satellites were crushed into a thousand equal fragments, the bulk of one of these fragments would be comparable with that of the new satellite.