An Improvement in the Method of Revolving together the Polarizing and Analysing Prisms of Petrological and other Microscopes.
Year: 1888

page_text: Date of Application, 13th Sept., 1888
Complete Specification Left, 16th May, 1889-Accepted, 13th July, 1889
PROVISIONAL SPECIFICATION.
An Improvement in the Method of Revolving together the Polarizing
and Analysing Prisms of Petrological and other Microscopes.
JAMES SWIFT, Optician 81, Tottenham Court Road, London, do hereby declare the
nature of this invention to be as follows:-
An improvement in the method of revolving together the polarizing and analysing
prisms of Petrological & other Microscopes, by causing them to turn together in their
crossed position. By this means, the object under examination need not be revolved
as in the ordinary way, but can be kept stationary during the rotation of the two
prisms. I effect the combined rotation of the polarizing and analysing prisms by
geared or friction wheels, or a metal chain. The driving wheels for giving motion to
each prism, are mounted on the ends of an extending or depressing rod for allowing
for the difference in focus of various power objectives 'used.
Dotal this Thistranth day of Contemben 1000
.
COMPLETE SPECIFICATION.
An Improvement in the Method of Revolving together the Polarizing
and Analysing Prisms of Petrological and other Microscopes.
1 James Swift, S1 Tottenham Court Road, London, Optician, do hereby declare
the nature of this invention and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :—
This invention relates more particularly to what are known as Petrological Micro-
scopes, used for the examination of rocks and crystals, the object of the invention
being to cause the synchronous rotation of the polarization and analysing prisms, by
which means the object under examination need not be rotated or otherwise shifted,
as has hitherto been the case, but may, when once brought into the field, remain
stationary while the examination is taking place.
In the accompanying drawing, I have shown in side elevation, at Fig. 1, a micro-
scope constructed according to my invention, Fig. 2 being a cross section on the
line XX, Fig. 1, above the stage.
A is the stand or foot, B is the frame, and C the body or barrel, all of which may
be of the usual construction. D is the eye piece tube, to which is pivotted, in any
convenient manner, the tube D' carrying the analysing prism, which is capable of
independent rotation in the usual manner. Upon the eye piece tube D, is mounted a
toothed wheel E, which gears with a toothed wheel E¹ mounted on one end of a rod
or axle E, formed of pinion wire.
Below the stage, which in this case has neither sliding or rotating movements, is
mounted the polarising prism F, also capable of independent rotation, upon the tube
of which is mounted a toothed wheel F, of the same size as the wheel E.-This
wheel F gears with a toothed wheel F, mounted on the lower end of a tube F³.-
This tube F³ is formed with internal recesses corresponding to the ribs on the pinion
wire E, into which recesses the said ribs fit.
The object of this arrangement is to allow for the raising and lowering of the body
of the microscope in accordance with the requirements as to focussing for the various
objectives used.
It will thus be seen that a sliding connection is made between the analysing and
polarising prisms, and that both may be rotated synchronously either from above or
from below the stage.

page_text: Upon the. polarizer tube, beneath the wheel F¹, I arrange a goniometer scale G,
which, in combination with crossed threads in the eye-piece, will allow of the
measurement of the different angles of crystals, without the necessity for shifting
the object under examination.
The instrument will be provided with a suitable, fine adjustment, such as H.
I is a set screw, by means of which the polariser, analyser, and goniometer, may be
fixed in any desired position.
J is a slide, provided with a lens and diaphragm of small aperture, which may be
used for the purpose of shewing optical pictures in minute crystals. K is a similar
slide fitted with a double convex lens for shewing the optic' rings round the axis of
crystals.
In figure 2, L is the achromatic condenser, and L is a slide fitted in the stage,
and furnished with a lens, which slide may be pushed in without disturbing the
object for the purpose of increasing the angle of the condenser when using high
power objectives.
Having now particularly described and ascertained the nature of iny said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
Connecting the analysing & polarising prisms in a microscope in such a manner
that they may be synchronously rotated, as and for the purpose set forth.
NEWTON & SON,
Agents for the Applicant.