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380 light-observations seems to indicate that the total mass of those at present known is many hundred times less than this limit.

295. Neptune and the minor planets are the only planets which have been discovered during this century, but several satellites have been added to our system.

Barely a fortnight after the discovery of Neptune (1846)

a satellite was detected by William Lassell (1799–1880) at Liverpool. Like the satellites of Uranus, this revolves round its primary from east to west—that is, in the direction contrary to that of all the other known motions of the solar system (certain long-period comets not being counted).

Two years later (September 16th, 1848) William Cranch Bond (1789–1859) discovered, at the Harvard College