The mechanical part is the successful
work of Mr. Gautier, who has looked after every detail with the
greatest care, and has thus realized a true _chef d'oeuvre_. The
colossal instrument, the total weight of which is 26,400 lb., is
maneuvered by hand with the greatest ease. A clockwork movement, due
to the same able manufacturer, is capable, besides, of moving the
instrument with all the precision desirable, and of permitting it to
follow the stars in their travel across the heavens. A star appearing
in the horizon can thus be observed from its rising to its setting.
The astronomer, his eye at the ocular, is always conveniently seated
at the same place, observing the distant worlds, rendered immovable,
so to speak, in the field of the instrument. For stars which, like the
moon and the planets, have a course different from the diurnal motion,
it is possible to modify the running of the clockwork, so that they
can thus be as easily followed as in the preceding case. Fig. 1 gives
a general view of the new installation, for which it became necessary
to build a special edifice 65 ft. in height on the ground south of the
observatory bordering on the Arago Boulevard. A large movable
structure serves for covering the external part of the instrument.
This structure rests on rails, upon which it slides toward the south
when it is desired to make observations.
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