to see them
just as we do. When we look up to the sky, we study ancient history;
we do not see the stars as they ARE, but as they WERE years, centuries,
even millennia ago.

The information derived from the parallax of a star by no means halts
with the disclosure of the distance of that body. Distance known, the
proper motion of the star, hitherto only to be reckoned as so many
seconds of arc, may readily be translated into actual speed of progress;
relative brightness becomes absolute lustre, as compared with the sun;
and in the case of the double stars the absolute mass of the components
may be computed from the laws of gravitation. It is found that stars
differ enormously among themselves in all these regards. As to speed,
some, like our sun, barely creep through space--compassing ten or twenty
miles a second, it is true, yet even at that rate only passing through
the equivalent of their own diameter in a day. At the other extreme,
among measured stars, is one that moves two hundred miles a second; yet
even this "flying star," as seen from the earth, seems to change its
place by only about three and a half lunar diameters in a thousand
years. In brightness, some stars yield to the sun, while others surpass
him as the arc-light surpasses a candle. Arcturus, the brightest
measured star, shines like two hundred suns; and even this giant orb is
dim beside those other stars which are so distant that their parallax
cannot be measured, yet which greet our eyes at first magnitude. As to
actual bulk, of which apparent lustre furnishes no adequate test, some
stars are smaller than the sun, while others exceed him hundreds or
perhaps thousands of times. Yet one and all, so distant are they, remain
mere disklike points of light before the utmost powers of the modern
telescope.

Revelations of the Spectroscope

All this seems wonderful enough, but even greater things were in store.
In 1859 the spectroscope came upon the scene, perfected by Kirchhoff
and Bunsen, along lines pointed out by Fraunhofer almost half a century
before. That marvellous instrument, by revealing the telltale lines
sprinkled across a prismatic spectrum, discloses the chemical nature
and physical condition of any substance whose light is submitted to it,
telling its story equally well, provided the light be strong enough,
whether the luminous substance be near or far--in the same room or at
the confines of space. Clearly such an instrument must prove a v