Year: 1897

page_text: A communication from abroad by CHARLES S. ROCKSTUHL, of 514, Elm Street,
St. Louis, United States of America, Manufacturers' Agent.
I, JAMES GRIEVE LORRAIN, M.I.E.E., M.I. Mech. E., of Norfolk House, Victoria
Embankment, London, W.C., Chartered Patent Agent, do hereby declare the nature
of this invention (as communicated to me from abroad) to be as follows:-
This invention relates to thermometers, more especially to the class known as
fever thermometers and has for its object to facilitate the reading thereof. It con-
sists in arranging streaks close alongside of the cylindrical edge lens to indicate
the direction of vision and to render the mercury column more distinct by contrast
with such streaks and by avoiding the confusion arising from surface reflection.
Fever thermometers are made of glass tubes of such small calibre that special
devices are required to enable one to read the indications thereof. One of such
devices consists in making the tube in the form of a triangular prism, one side of
which is made of or contains a white opaque substance and the edge opposite this
aide is rounded to constitute a cylindrical lens focussing on the thread of mercury.
When this rounded edge is exactly in the line between the mercury and the eye,
the direct ray from the thread of mercury emerges from the tube at right angles
to its surface and therefore without deflection but the rays from the mercury
which strike the surfaces of the prism, or rather the cylindrical lens portion thereof,
are refracted as they emerge from the glass into the air, the deflection being towards
the direct line. The mercurial thread is thus seen simultaneously by means of
the direct undeflected ray and by the other rays emerging from the lens portion.
The combined effect of these several rays, each of which shows the image of the
mercury in a different position overlapping the image of the next adjacent rays,
is apparently to magnify the width of the mercury thread. When the width of this
thread is thus magnified, its height can be readily observed and the reading of the
thermometer ascertained.
The disadvantage of this device is that it requires to be held in one precise
position, a very slight deviation from which renders the device useless. The result
is that in the hands of inexperienced persons, the device frequently fails entirely
in its object: and even in the hands of experienced users, it is liable to cause annoy-
ance, because every time it is used, the tube has to be shifted to and fro to ascertain
experimentally the precise line of vision. The strong reflection of light rays from
the surfaces of the prism is liable to be very confusing in this operation, especially
to inexperienced users.
Now the present invention utilizes the structural arrangement above described,
as the basis of improvement. On each side of the rounded edge is arranged a
streak or line of some colour against which the mercury will show clearly. These
lines or streaks may be made by painting the surfaces of the prism with narrow

page_text: streaks of a material whose reflecting power is low; the streaks are made narrow
enough not to intercept in an excessive degree the light rays necessary to illuminate
the mercury.
The only position in which the mercury thread appears magnified is between
the streaks or lines thus formed on each side of the rounded edge. These streaks
should bound closely on the magnifying field of the edge lens and be as close
together as is practicable to obtain the full magnifying effect. They thus indicato
within a small angle the line of sight for the mercury thread, and by the contrast
of colours or by their unreflecting surfaces, facilitate the reading of the ther-
mometric indication.
Whilst this device is primarily designed for fever thermometers, it is obviously
applicable to other similar apparatus; and its use is not to be considered as limited
to such thermometers.
J. G. LORRAIN,
Chartered Patent Agent.
A communication from abroad by CHARLES SCHIMPF RUCKSTUHL, of 514, Elm Street,
St. Louis, United States of America, Manufacturers' Agent.
I, JAMES GRIEVE LORRAIN, M.I.E.E., M.I. Mech. E., of Norfolk House, Victoria
Embankment, London, W.C., in the County of Middlesex, Chartered Patent Agent,
do hereby declare the nature of this invention (as communicated to me from abroad)
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 to fever thermometers and has for its object to facilitate
the reading thereof.
It consists in arranging streaks of low reflecting power on the surface of the
therinometer close alongside of the cylindrical edge lens to indicate the direction
of vision and to render the mercury column more distinct by contrast with such
streaks and by avoiding the confusion arising from surface reflection.
In the accompanying drawings, which form part of this specification, Figure I
is a front view of a fever thermometer provided with my invention, and Figure II
is a cross sectional view thereof.
Fever thermometers are made of glass tubes of such small calibre that special
devices are required to enable one to read the indications thereof. One of such
devices consists in making the tube in the form of a triangular prism, one side of
which is made of or contains a white opaque substance, and the edge opposite this
side is rounded to constitute a cylindrical leus focussing on the thread of mercury.
When this rounded edge is exactly in the line between the mercury and the eye,
the direct ray from the thread of mercury emerges from the tube at right angles
to its surface and therefore without deflection; but the rays from the mercury
which strike the surfaces of the prism, or rather the cylindrical lens portion thereof,
are refracted as they emerge from the glass into the air, the deflection being towards
the direct line. The mercurial thread is thus seen simultaneously by means of
the direct undeflected ray and by the other rays emerging from the lens portion.
The combined effect of these several rays, each of which shows the image of the

page_text: mercury in a different position overlapping the image of the next adjacent rays,
is apparently to magnify the width of the mercury thread. When the width of
this thread is thus magnified, its height can be readily observed and the reading
of the thermometer ascertained.
The disadvantage of this device is that it requires to be held in one precise
position, a very slight deviation from which renders the device useless. The result
is that in the hands of inexperienced persons the device frequently fails entirely
in its object, and even in the hands of experienced users it is liable to cause annoy-
ance, because every time it is used the tube has to be shifted to and fro to uscer-
tain experimentally the precise line of vision. The strong reflection of light raya
from the surfaces of the prism is liable to be confusing in this operation, especially
to inexperienced users.
My invention utilizes the structural arrangement above described as the basis
of improvement. On each side of the rounded edge is arranged a streak or line of
some colour against which the mercury will show clearly. These lines or streaks, 1,
may be made by painting the surfaces of the prisni with narrow streaks of a
material whose reflecting power is low. The streaks are made narrow enough not
to intercept in an excessive degree the light rays necessary to illuminate the
mercury. The only position in which the mercury thread appears magnified is
between the streaks or lines thus formed on each side of the rounded edge. These
streaks should bound closely on the magnifying field of the edge lens and be as
close together as is practicable to obtain the full magnifying effect. They thus
indicate within a small angle the line of sight for the mercury thread and by
the contrast of colours or by their unreflecting surfaces facilitate the reading of
the thermometric indication.
While my device is primarily designed for fever thermometers, it is obviously
applicable to other similar apparatus, and I do not wish to be limited to its use
in connection with such thermometers.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed (as communicated to me
from abroad), I declare that what I claim is--
A prismatic thermometer having one edge formed into a cylindrical lens adapted
to magnify the image of the thread of mercury, and having narrow coloured streaks
of low reflecting power on its surface alongside of the edge lens for indicating the
place to look for the magnified image of the mercury thread and for rendering
such image more easily visible said streaks being narrow so as not to intercept the
mercury illuminating light-rays excessively, substantially as set forth.
TY
11. 04h dave of Uuntambar 1898