--1 illustration
XI. RAILWAY ENGINEERING.--Improved Hand Car.--A novelty
in the construction of hand cars, avoiding the production of a
dead center.--1 illustration
XII. TECHNOLOGY.--The Tanning Materials of Europe.--The natural
tanning materials and pathological or abnormal growth tanning
materials described and classified, with relative power
* * * * *
THE GREAT EQUATORIAL OF THE PARIS OBSERVATORY.
The great instrument which has just completed the installation of our
national observatory is constructed upon the same principle as the
elbowed equatorial, 11 in. in diameter, established in 1882, according
to the ingenious arrangement devised as long ago as 1872, by Mr.
Loewy, assistant director of the Paris Observatory.
We shall here recall the fact that the elbowed equatorial consists of
two parts joined at right angles. One of these is directed according
to the axis of the world, and is capable of revolving around its own
axis, and the other, which is at right angles to it, is capable of
describing around the first a plane representing the celestial
equator. At the apex of the right angle there is a plane mirror of
silvered glass inclined at an angle of 45 deg. with respect to the
optical axis, and which sends toward the ocular the image coming from
the objective and already reflected by another and similar plane
mirror.
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