light.' It might even be supposed, they urge, that the star in the
Crown, by its swift motion, may have come in contact with one of the
star clouds which exist in large numbers in the realms of space. 'Such a
collision would necessarily set the star in a blaze and occasion the
most vehement ignition of its hydrogen.'

Fortunately, our sun is safe for many millions of years to come from
contact from any one of its planets. The reader must not, however, run
away with the idea that the danger consists only in the gradual
contraction of planetary orbits sometimes spoken of. That contraction,
if it is taking place at all, of which we have not a particle of
evidence, would not draw Mercury to the sun's surface for at least ten
million millions of years. The real danger would be in the effects which
the perturbing action of the larger planets might produce on the orbit
of Mercury. That orbit is even now very eccentric, and must at times
become still more so. It might, but for the actual adjustment of the
planetary system, become so eccentric that Mercury could not keep clear
of the sun; and a blow from even small Mercury (only weighing, in fact,
390 millions of millions of millions of tons), with a velocity of some
300 miles per second, would warm our sun considerably. But there is no
risk of this happening in Mercury's case--though the unseen and much
more shifty Vulcan (in which planet I beg to express here my utter
disbelief) might, perchance, work mischief if he really existed.

As for star clouds lying in the sun's course, we may feel equally
confident. The telescope assures us that there are none immediately on
the track, and we know, also, that, swiftly though the sun is carrying
us onwards through space,[34] many millions of years must pass before he
is among the star families towards which he is rushing.

Of the danger from combustion, or from other causes of ignition than
those considered by Meyer and Klein, it still remains to speak. But
first, let us consider what new evidence has been thrown upon the
subject by the observations made on the star which flamed out last
November.

The new star was first seen by Professor Schmidt, who has had the good
fortune of announcing to astronomers more than one remarkable
phenomenon. It was he who discovered in November 1866 that a lunar
crater had disappeared, an announcement quite in accordance with the
facts of the case. We have seen that he was one of the independent
dis