largest moon, is merely a point of light as compared with the planet,
as it appears in a telescope, yet it has been seen, so it is said,
with a one inch glass. The shadow of this satellite, while crossing
the face of Saturn, has been observed by Banks with a two and
seven-eighths objective. By hiding the glare of the planet behind an
occulting bar, some of Saturn's smallest moons were seen by Kitchener
with a two and seven-tenths aperture and by Capron with a two and
three-fourths one. Banks saw four of them with a three and
seven-eighths telescope, Grover two of them with a three and
three-quarter inch, and four inches of aperture will show five of
them, so Webb says. Rhea, Dione and Tethys are more minute than
Japetus, yet Cassini, with his inferior means, discerned them and
traced their periods. Take the instance of Mars next. It was long
believed that Mars had no satellites. But in 1877, during one of the
highly favorable oppositions of that planet which occur but once in
about sixteen years, the able Hall, using the great 26 inch refractor
at Washington, discovered two tiny moons which had never been seen
before. One of these, called Deimos, is only six miles in diameter,
the other, named Phobos, is only seven, and both are exceedingly close
to the primary and in rapid revolution. The diameter of these
satellites is really less than the distance from High Park, on the
west of Toronto, to Woodbine race course, on the east of the city. No
wonder these minute objects--seldom, if ever, nearer to us than about
forty millions of miles--are difficult to see at all. Newcomb and
Holden tell us that they are invisible save at the sixteen year
periods referred to, when it happens that the earth and Mars, in their
respective orbits, approach each other more nearly than at any other
time. But once discovered, the rule held good even in the case of the
satellites of Mars. Pratt has seen Deimos, the outermost moon, with an
eight and one-seventh inch telescope; Erek has seen it with a seven