IMPROVEMENTS IN INSTRUMENTS FOR POLARISING LIGHT
Year: 1884

page_text: I, THOMAS BAYLEY, of 7 Broad St Corner, Birmingham, Analytical Chemist
do hereby declare the nature of my invention for IMPROVEMENTS IN INSTRUMENTS
FOR POLARISING LIGHT to be as follows:-
My invention consists in improvements in certain optical instruments which are
employed for the purpose of demonstrating, observing, or measuring the rotation
effected upon the plane of a ray of polarised light by various bodies, whether in
their natural condition, in solution in other bodies, or when under the influence of
magnetic or electric forces. In certain of these instruments a half wave plate of
quartz cut parallel to the optical axis of the crystal is so disposed between the
polarising and analysing prisms or portions of the instrument that it covers a
portion of the field of vision as seen through the eye piece of the instrument. The
function of this quartz plate is to confer increased sharpness of reading upon the
instrument as compared with those in which no similar or equivalent construction
is employed.
My invention consists in substituting for this quartz plate a single thin section
of the mineral known as mica. This section is obtained by splitting the crystal
along its natural planes of cleavage to the particular thickness which experiment
shows to be most sensitive.
The plate of mica so prepared is then mounted and placed between the polarizing'
and analysing portions of the apparatus so as to cover a portion of the field of
vision. The variety of mica which I find most suitable is that known as Muscovite
and often in trade circles called talc.

page_text: Improvements in Instruments for Polarizing Light.
I, TпоMAS BAYLEY, of 7 Broad St., Corner Birmingham Analytical Chemist
do hereby declare the nature of my invention for IMPROVEMENTS INSTRUMENTS
FOR POLARIZING LIGHT and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
1
My invention consists in improvements in certain optical instruments which are
employed for the purpose of demonstrating, observing or measuring the rotation
effected upon the plane of a ray of polarised light by various bodies whether in
their natural condition, in solution, in other bodies, or when under the influence of
magnetic or electric forces. In certain of these instruments a half wave plate of
quartz cut parallel to the axis of the crystal is so disposed between the polarising
and analysing prisms or portions of the apparatus that it covers a portion of the
field of vision as seen through the eye piece of the instrument. The function of
this quartz plate is to confer increased sharpness upon the instrument as compared
with those in which no similar or equivalent construction is employed.
My invention consists in substituting for this quartz plate a single thin section
of the mineral known as mica. This section is obtained by splitting the crystal
along its natural planes of cleavage to the particular thickness which experiment
shows to give the best result viz. the greatest degree of sensitiveness in the
instrument. The plate of mica so prepared is then mounted in balsam between
sheets of glass, or in some other suitable manner, and placed between the polarizing
and analysing portions of the apparatus so as to cover a portion of the field of
vision. The variety of mica which I find most suitable is that known as Muscovite
and often in trade circles called talc.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed I declare that what i
I claim is
The use of a single thin sheet of mica to replace the half wave plate of quartz
used in certain Polariscopes or Instruments for polarizing light,