of the earth.* That distance he held to be
the only cause of the small apparent dimensions
they offer to our view. But observation
has revealed a circumstance which
prevents our adopting those notions
respecting their real nature.
* See ALL THE YEAR AROUND, New Series, vol. iii., p. 2.

At certain epochs, there occurs a
considerable increase in the number of
shooting stars seen within a given time. The
frequency of their appearance even becomes
so great as to give it all the character of
a veritable shower of stars. If shooting
stars and bolides were really identical, the
latter, together with the showers of aerolites
which often accompany them, ought especially
to show themselves at the same time
as the grand displays of shooting stars.
Now, nothing of the kind takes place. The
two sets of phenomena appear to have
no connexion whatever with each other.
Shooting stars seem to be of a nature
peculiar to themselves; and it is only by
studying them directly that we can hope
to obtain information respecting the cause
of this curious phenomenon.

No doubt, as soon as it is granted that
meteors are solid bodies existing in space,
which the earth falls in with while revolving
in her orbit, it is very natural to admit
that something analogous is the cause of
shooting stars, and to regard them also as
betraying the presence of certain bodies in
the portion of space traversed by the earth.
Nevertheless, the capital circumstance just
pointed out, and from which it results that
meteors and shooting stars constitute two
distinct orders of phenomena, has raised
and left doubts respecting the real nature
of shooting stars. Some philosophers have
persisted in assigning to them a purely
atmospheric origin, and have even
endeavoured to find in them a clue to the
meteorological phenomena of which our
atmosphere is the seat. Recent discoveries,
however, have removed all doubt upon the
subject; the atmospheric theory of shooting
stars must henceforth be abandoned.
We will succintly follow M. Delaunay in
his statement of the clear and precise
notions respecting this matter which we
now possess.

The first thing to be done, in the study
of shooting stars, is to ascertain their
distance from us. The observations required
for that purpose are very simple. Two
observers stationed at different spots
sufficiently distant from each other, will not
behold the same shooting star to be tracing
the same course across the firmament. The
straight lines drawn from the two places
of observation to the shooting star, will
cross at that point (namely, the shooting
star), and then diverge until they reach
two different points on the celestial vault.
Other circumstances being the same, the
two points of the celestial sphere on which
the shooting star is projected at any given
instant, for each one of the two observers,
will be the more distant from each other
the nearer the shooting star is to the earth.
Hence it will be easily understood that, by
certain calculations which there is no need
to detail here, the height of a shooting star
above the earth's surface may be ascertained
from data, furnished by its simultaneous
observation at two different spots.
It is the same process as the method
employed by astronomers to determine the
parallax of a heavenly body, and consequently
its distance from the earth.*
* See ALL THE YEAR ROUND, first Series, vol. xix.,
p. 174.

The first observations in accordance with
this method date from 1798. They were
made by Brandes and Benzenberg, then
students in the university of Gottingen.
Until then, there existed no observations
of shooting stars: except that Bridone, in
his "Tour through Sicily," states that he
saw them exactly the same, from the
summit of Mount St. Bernard, in Switzerland,
and of Mount Etna in Sicily, as on the sea
shore. The conclusion was, that a very
considerable altitude may be assigned to
shooting stars. By comparing the different
results obtained between 1798 and 1863,
Alexander Herschel (the grandson of
William) found the average height of a shooting
star above the earth to be, at the
commencement of its appearance, one hundred
and thirteen kilometres, and at the end,
eighty–seven. Mr. Newton, of Newhaven,
United States, arrived at the respective
numbers of one hundred and eighteen and
eighty–one kilometres; Father Secchi, of
Rome, found them to be one hundred and
twenty, and eighty kilometres respectively.
The agreement between these different
results is as satisfactory as can be wished.
We may fairly take Secchi's figures as
representing in round numbers the average
height of a shooting star above the earth,
at the beginning and at the end of its
appearance. Those figures, reduced to
English miles, also in round numbers, are
seventy–five and fifty respectively. Seventy–five
miles above the earth's surface being
not an extreme but an average height, it