s a far
more glorious orb than our Sun. According to recent photometric
measurements it emits seventy times the quantity of light, and is three
times more massive than the great luminary of our system. At the
distance of Sirius (fifty billions of miles) the Sun would shrink to the
dimensions of a third-magnitude star, and the light of seventy such
stars would be required to equal in appearance the brilliant radiance of
the great dog-star. The orb, with his retinue of attendant worlds--some
of which are reported as having been seen--is travelling through space
with a velocity of not less than 1,000 miles a minute.

An irregularity of motion resembling that of Sirius has been detected
with regard to Procyon, the lesser dog-star. But in this case the
companion star has not as yet been seen, though a careful search has
been made for it with the most powerful of telescopes. Should it be a
planetary body, illumined by its primary, its reflected light would not
appear visible to us, even if it were much less remote than it is.

We are able only to perceive the effulgence of brilliant suns scattered
throughout the regions of space; but besides those, there are doubtless
many faintly luminous orbs and opaque bodies of vast dimensions
occupying regions unknown to us, but by a knowledge of the existence of
which an enlarged conception is conveyed to our minds of the greatness
of the universe.

The most rapid of known revolving pairs is Delta Equulei. The components
are so close that only the finest instruments can separate them, and
this they cannot do at all times. They accomplish a revolution in eleven
and a half years. The slowest revolving pair is Zeta Aquarii. The motion
of the components is so tardy that to complete a circuit of their orbits
they require a period of about sixteen centuries. Other binary stars
have had different periods assigned to them; eleven pairs have been
computed to revolve round each other in less than fifty years, and
fifteen in less than 100 but more than fifty. There are other compound
stars whose motions appear to be much more leisurely than those just
mentioned, and although no orbital movement has, so far, been detected
among them, yet, so vast is the scale upon which the sidereal system is
constructed, that thousands of years must elapse before they can have
accomplished a revolution of their orbits.

The Pole Star is an optical double, but the components are of very
unequal magnitude. The P