in utter ignorance whether the
space between him and Mercury is occupied or not by some other denizen of
the planetary system. To enable us to explore the sun's immediate
proximity, we require a body that shall exclude his rays from our
atmosphere, and yet leave the space round the sun open to our view. Such
an object can of course be neither a cloud nor any terrestrial object,
natural or artificial, since parts of the atmosphere will exist behind it
which will be impinged on by the sun's rays. Only during a total eclipse
can these conditions be fulfilled, and even then but for a very brief
interval, which may still be lost to the observer through unfavorable
weather or from too low a position of the sun.

Notwithstanding that this rare and precarious opportunity is the only
possible one we possess of becoming better acquainted with the physical
nature of the great luminary of day, astronomers never availed themselves
of it for any other purpose than the admeasurement of the earth, which
might have been done as well, if not better, during any planetary eclipse.
This error or indifference, whichever it may have been, can not, however,
be laid to the charge of our living astronomers. The 8th of July, 1842--the
day on which the last total eclipse of the sun took place--witnessed the
most distinguished of these assembled for the purpose of making, for the
first time, observations calculated to afford us some insight into this
greatest mystery of the celestial world. This eclipse was total on a zone
which traversed the north of Spain, the south of France, the region of the
Alps and Styria, and a portion of Austria, Central Russia and Siberia,
terminating in China; so that the observatories of Marseilles, Milan,
Venice, Padua, Vienna, and Ofen, all supplied with excellent telescopes,
and in full activity, came within its range; while many astronomers, at
whose observatories the eclipse was not visible, set out for places
situated within the zone just described. Thus Arago and two of his
colleagues repaired to Perpignan, Airy to Turin, Schumacker to Vienna,
Struve and Sehidloffsky to Lipezk, and Stubendorff to Koerakow. Most of
them were favored by the weather. Let us now see what the combined
endeavors of these practiced and well-furnished observers have made us
acquainted with.

First, as regards the obscurity, it was so great, that five, seven, and in
some cases as many as ten stars were visible to the naked eye. A reddish