be well seen only for a month or two before and after each
opposition. It is hopeless to look for the satellites of Mars with
any but the greatest telescopes of the world. But the markings on
the surface, from which the time of rotation has been determined,
and which indicate a resemblance to the surface of our own planet,
can be well seen with telescopes of six inches aperture and
upward. One or both of the bright polar spots, which are supposed
to be due to deposits of snow, can be seen with smaller telescopes
when the situation of the planet is favorable.

The case is different with the so-called canals discovered by
Schiaparelli in 1877, which have ever since excited so much
interest, and given rise to so much discussion as to their nature.
The astronomer who has had the best opportunities for studying
them is Mr. Percival Lowell, whose observatory at Flaggstaff,
Arizona, is finely situated for the purpose, while he also has one
of the best if not the largest of telescopes. There the canals are
seen as fine dark lines; but, even then, they must be fifty miles
in breadth, so that the word "canal" may be regarded as a
misnomer.

Although the planet Jupiter does not present such striking
features as Saturn, it is of even more interest to the amateur
astronomer, because he can study it with less optical power, and
see more of the changes upon its surface. Every work on astronomy
tells in a general way of the belts of Jupiter, and many speculate
upon their causes. The reader of recent works knows that Jupiter
is supposed to be not a solid mass like the earth, but a great
globe of molten and vaporous matter, intermediate in constitution
between the earth and the sun. The outer surface which we see is