he earth. What is it? Every
attempt to detect it has been in vain. Professor Hale, at the Yerkes
Observatory, has had in operation from time to time, for several years,
his ingenious spectroheliograph, which photographs the sun by a single
ray of the spectrum. This instrument shows that violent actions are
going on in the sun, which ordinary observation would never lead us to
suspect. But it has failed to show with certainty any peculiar
emanation at the time of a magnetic storm or anything connected with
such a storm.

A mystery which seems yet more impenetrable is associated with the
so-called new stars which blaze forth from time to time. These offer to
our sight the most astounding phenomena ever presented to the physical
philosopher. One hundred years ago such objects offered no mystery.
There was no reason to suppose that the Creator of the universe had
ceased His functions; and, continuing them, it was perfectly natural
that He should be making continual additions to the universe of stars.
But the idea that these objects are really new creations, made out of
nothing, is contrary to all our modern ideas and not in accord with the
observed facts. Granting the possibility of a really new star--if such
an object were created, it would be destined to take its place among
the other stars as a permanent member of the universe. Instead of this,
such objects invariably fade away after a few months, and are changed
into something very like an ordinary nebula. A question of transcendent
interest is that of the cause of these outbursts. It cannot be said
that science has, up to the present time, been able to offer any
suggestion not open to question. The most definite one is the collision
theory, according to which the outburst is due to the clashing together
of two stars, one or both of which might previously have been dark,
like a planet. The stars which may be actually photographed probably
exceed one hundred millions in number, and those which give too little
light to affect the photographic plate may be vastly more numerous than
those which do. Dark stars revolve around bright ones in an infinite
variety of ways, and complex systems of bodies, the members of which
powerfully attract each other, are the rule throughout the universe.
Moreover, we can set no limit to the possible number of dark or
invisible stars that may be flying through the celestial spaces. While,
therefore, we cannot regard the theory of collision as