IMPROVE- MENTS IN MOUNTING TELESCOPES AND' MICROSCOPES
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by Carl Johann Reinhart Jähns at
the Office of the Commissioners of Patents, with his Petition, on the
10th August 1865..
I, CARL JOHANN REINHART JAINS, of Krausenstrasse, No. 62, Berlin,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN MOUNTING TELESCOPES AND' MICROSCOPES," to be as follows:
This Invention has for its object improvements in mounting telescopes and
microscopes. In' arranging télescopes for the purpose of measuring angles
the telescope is mounted on an axis, or otherwise, so as to be free to move
only in one plane, namely, the plane of the angle to be measured, and a disc
or flat surface is caused to bear on the telescope so as to touch it only in a
straight line parallel with its axis. The disc or flat surface is also-mounted.
on an axis or is otherwise so arranged that it can be rotated' truly and steadily,.
the axis of rotation being in the plane of motion of the telescope, and inclined
at a certain known angle to the disc or flat surface. With this arrangement.
it will be seen that when the disc or flat surface is turned round the telescope
is at the same time moved, and when the disc or flat surface has been turned
one quarter round or through an angle of 90° the telescope will have swept
over an arc equal to the angle of inclination of the dise to its axis of rotation,
and when the disc or flat surface is turned half round the arc swept over by
the telescope will be double this angle. In connection with the disc or flat
surface is a graduated semicircle, on which the angle through which the dise
or flat surface is moved can be accurately measured, and the arc swept over
by the telescope is thus ascertained as it is proportional to the angle, so

page_text: measured.
If the disc or flat surface and its axis are nearly at right angles,
the angle of inclination being very small, the are swept over by the telescope
will bear a very small proportion to the angle through which the disc or flat
surface is moved, and the arc will consequently be very accurately ascertained;
if the angle of inclination is greater, the arc also is increased, but the instru
ment will not be able to measure it with the same accuracy. In most cases.
it is convenient that the graduated semicircle should be so divided that the
arc swept by the telescope may be read off directly. It is obvious that the
details of the arrangement may be much varied, the principle of using a plane
surface capable of rotating on an axis inclined to it and bearing on the
telescope along a single straight line being still maintained.
A useful application of the principle is in instruments for measuring
distances. The instrument in this case.consists of a frame suited to be held
in the hand of the observer, in this frame two telescopes are mounted, one is
rigidly fixed to it, the other by the means already described is capable of
being set at any required small angle to the first. The observer in using the
instrument looks through the two telescopes at the same time, the distance
between them corresponding to that between the eyes, and the observer then
adjusts the moveable telescope until he finds that the axes of the two telescopes
can be brought to bear simultaneously on one point, in the object of which
the distance is required, and then by reading on the graduated semicircle
: this distance is ascertained. In using microscopes it is frequently necessary
or desirable to be able to see the object from many different points of view,
to facilitate this I support the object on a stage or surface which itself rests
on a plane which is capable of being rotated about an axis inclined to it, then
by rotating this plane a rolling motion is given to the stage and to the object
it supports, each side of which is consequently brought into view. It is con-
venient that the plane surface above mentioned should be the end of a
cylinder cut off at an inclination to its axis, and in this case the other end. of
the same cylinder may be cut off square and rest on a stage at right angles
to the axis of the microscope.