signs are not wanting that it may be
found so in this case. It is possible that the monumental domes and huge
movable tubes of our present observatories will, in a few decades, be as
much things of the past as Huygens's "aerial" telescopes. It is certain
that the thin edge of the wedge of innovation has been driven into the
old plan of equatoreal mounting.

M. Loewy, the present director of the Paris Observatory, proposed to
Delaunay in 1871 the direction of a telescope on a novel system. The
design seemed feasible, and was adopted; but the death of Delaunay and
the other untoward circumstances of the time interrupted its execution.
Its resumption, after some years, was rendered possible by M.
Bischoffsheim's gift of 25,000 francs for expenses, and the _coude_ or
"bent" equatoreal has been, since 1882, one of the leading instruments
at the Paris establishment.

Its principle is briefly this: The telescope is, as it were, its own
polar axis. The anterior part of the tube is supported at both ends, and
is thus fixed in a direction pointing towards the pole, with only the
power of twisting axially. The posterior section is joined on to it at
right angles, and presents the object-glass, accordingly, to the
celestial equator, in the plane of which it revolves. Stars in any other
part of the heavens have their beams reflected upon the object-glass by
means of a plane rotating mirror placed in front of it. The observer,
meanwhile, is looking steadfastly down the bent tube towards the
invisible _southern_ pole. He would naturally see nothing whatever were
it not that a second plane mirror is fixed at the "elbow" of the
instrument, so as to send the rays which have traversed the object-glass
to his eye. He never needs to move from his place. He watches the stars,
seated in an arm-chair in a warm room, with as perfect convenience as if
he were examining the seeds of a fungus with a microscope. Nor is this a
mere gain of personal ease. The abolition of hardship includes a vast
accession of power.[1645]

Among other advantages of this method of construction are, first, that
of added stability, the motion given to the ordinary equatoreal being
transferred, in part, to an auxiliary mirror. Next, that of increased
focal length. The fixed part of the tube can be made almost indefinitely
long without inconvenience, and with enormous advantage to the optical
qualities of a large instrument. Finally, the costly and unmanageable
cupola