Stimulated by this success, Leverrier calculated an
orbit for an interior planet from perturbations of Mercury,
but though prematurely christened Vulcan, this
hypothetical nursling of the sun still haunts the realm
of the undiscovered, along with certain equally hypothetical
trans-Neptunian planets whose existence has
been suggested by "residual perturbations" of Uranus,
and by the movements of comets. No other veritable
additions of the sun's planetary family have been made
in our century, beyond the finding of seven small moons,
which chiefly attest the advance in telescopic powers.
Of these, the tiny attendants of our Martian neighbor,
discovered by Professor Hall with the great Washington
refractor, are of greatest interest, because of their
small size and extremely rapid flight. One of them is
poised only six thousand miles from Mars, and whirls
about him almost four times as fast as he revolves,
seeming thus, as viewed by the Martian, to rise in the
west and set in the east, and making the month only
one-fourth as long as the day.


The Rings of Saturn

The discovery of the inner or crape ring of Saturn,
made simultaneously in 1850 by William C. Bond, at
the Harvard observatory, in America, and the Rev.
W. R. Dawes in England, was another interesting optical
achievement; but our most important advances
in knowledge of Saturn's unique system are due to the