CERTAIN IMPROVEMENTS IN AND ON THERMOME- TERS
Year: 1816

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
KEWLEY, of Aldersgate Street, in the City of London, Gentleman, serid
greeting.
WHEREAS His most Excellent Majesty King George the Third did, by His
Letters Patent under the Great Seal of the United Kingdom of Great Britain.
and Ireland, bearing date at Westminster, the Twenty-first day of November, in
the fifty-seventh year of His reign, give and grant unto me, the said James
Kewley, my exors, adiiors, and assigns, His especial licence, full power, solė privi-
lege and authority, that I, the said James Kewley, my exors, admňors, and assigns;
should and lawfully might, during the term of years therein expressed, make;-
use, exercise, and vend, within England, Wales, and the Town of Berwick:
upon-Tweed,' my Invention of "CERTAIN IMPROVEMENTS IN AND ON THERMOME-
TERS;" in which said Letters Patent there is contained a proviso that if I, the
said James Kewley, shall not particularly describe and ascertain the nature of
my said Invention, and in what manner the same is to be performed, by an
instrument in writing under my hand and seal, and cause the same to be
inrolled in His Majesty's High Court of Chancery within six calendar months
next and immediately after the date of the said Letters Patent, that then
the said Letters Patent, and all liberties and advantages whatsoever thereby
granted, shall utterly cease, determine, and become void, as in and by the;
same (relation being thereunto had) may more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
James Kewley, do hereby declare that the nature of my said Invention, and

page_text: the manner in which the same is to be performed, are particularly described
and ascertained in and by the Drawings hereunto annexed, and the following
description thereof, that is to say :—
I fix the tubes containing the the materials hereafter mentioned on two
centres, so that they may swing like the beam of a pair of scales, by which
means the comparative weight of the two ends of the balance, which varies in
proportion to the expansion or contraction of the materials of which the
thermometer is composed, which variations, it is well known to men of science,
is in consequence of the changes of temperature; the comparative weight being
therefore known, the comparative temperature is also thereby ascertained.
Now my improved thermometers, which I shall, for the sake of distinction, call
Balance Thermometers, possess this peculiar advantage over most thermome-
ters which indicate the temperature by the rise and fall of the fluid in the
tube or tubes, namely, that the length of each degree on the scale may be in
exact proportion to the expansion of the materials of which the thermometer
is composed, which in common thermometers can seldom or ever be the case,
in consequence of the difficulty of procuring tubes of an equal calibremy
balance thermometers have also this great advantage over thermometers in.
common use, namely, that they may be so adjusted that they will move on
their centres when the temperature is at any degree within the instrument's
range, so that they may be used as a first moving power to answer many
useful purposes; so as to put delicate machinery, with which mechanics are
well acquainted, into motion; for the purpose of ringing an alarm bell in case
of accidental fire; for regulating the temperature in hospitals, hothouses, and.
the like where a regular temperature may be desirable.. Now, from the
nature of my Invention, it will be obvious to men acquainted with the subject
that it is not necessary that the tubes should be the exact shape and dimen-
sions of the Drawings annexed, as an infinite variety of shapes and dimensions
will answer the same end; nor is it necessary that the apparatus in which the
glass is fixed should be exactly as in the Drawing; an infinite variety also in
that part of my Invention will produce the same effect, the essential point
being simply that the tube or tubes to be set on centres, and the glass so
constructed that when filled in a proper manner with proper fluids, that then,
by applying weights. or moving screws or racks, the temperature may be
known; but the Drawing represents the shape I prefer,. and alcohol and
quicksilver are the fluids I also prefer. I do hereby further declare, that I do
not claim the Invention of putting alcohol and quicksilver, or either of them,
or other fluids proper for the purpose, into glass tubes, and thereby ascertaining
the temperature; but I claim the Invention of fixing such tubes on centres so

page_text: that by the comparative weights of the two ends of the balance the tempera-
ture may be ascertained, and also other useful purposes effected.
Figs. 1 and 4 represent edge views of the clamping pieces, with their
binding screws a, a, which unite the two together and embrace the glass tubes,
the position of which tubes are described by the dotted lines b, b. The
external dotted lines at c represent a collar of thin leather used to. prevent the
pressure from breaking the tubes and to create friction, and thereby prevent-
ing the glass tubes from slipping. The screw at d, fixed to the upper part of
Figure 1, serves to elevate or lower the tubes, and to adjust them for gravity
when the two pieces are screwed together by the screws at a, a. Fig. 2
represents the hollow or internal part of Figure 1, with its two ears for the
screws a, a, to pass through. Fig. 3 shows the upper side of Fig. 2, the hole
at e being the place where the screw d is to be rivetted into. Fig. 5 shews
the internal or hollow part of Figure 4. The holes in the ears contain female
screws to receive the screws a, a, Fig. 6 shews the under side of Fig. 4.
Fig. 7 represents an end elevation of the main frame, a front elevation of
which is seen at Fig. 8. The hole f is to receive the pivot of a small pinion,
and the hole g is for the reception of a small screw. The two projecting studs
h, h, are fixed to the frame and serve the purpose of steadying the small spring.
Fig. 8 represents a front elevation of the frame which carries the centers upon
which the instrument is poised. i shews the situation of a mortice into which
the milled-headed nut Fig. 10 is placed, which nut has a female screw through
its centre, shewn at k. This being placed in the mortice i draws up the
screw d, Figs. 1 and 4, and with them the tubes, thereby adjusting them to
their proper centre of gravity. The ears affixed to Figs. 2, 3, 5, and 6, have
dovetailed ends to keep them steady as they slide up the inside of the frame,
the edges 1, 1, being filed so as to fit the before-mentioned dovetails. The small
cylinder m is screwed into the frame at n, and is one of the centres upon which
the tubes and frame are suspended. The end o is formed into a knife edge,
such as is commonly used in balances where great delicacy of action is
necessary. Fig. 10 is a plan of the milled-headed nut, and Fig. 11 a side or
edge view of the same. Fig. 9 represents a plan of the upper side of the
frame, the hole at p being the place where the screw d, Fig. 1, passes
through. Fig. 12 is an inside view of a piece of brass which serves, when
fixed to the frame Fig. 8, to receive the scale at Fig. 19.
to the frame the small pinion, shewn at Fig. 18, is withdrawn from its milled
head, and the end q is placed in the hole of f, Fig. 7; the piece of brass,
Fig. 12, is then fixed to its place by the screw r, as shewn, Fig. 21, the end
of the pinion coming through the hole s to receive the milled head. Fig. 16
Before this is fixed
.

page_text: represents a side view of a small spring, which is used to steady the scale, and
Fig. 17 is an edge view of the same. The position of the spring is shewn
at t, t, Fig. 21, the screw r serving to keep it in its place as well as fixing the
brass piece Fig. 12. In Fig. 12 two projections are shewn at v, v, which
embrace the side of the frame, and having screw holes in them, give additional
facility in fixing Fig. 12 to the main frame. Fig. 13 represents the upper
end view of Fig. 12, and Fig. 14 is an edge view in which may be seen
affixed the other centre upon which the tubes and frame are poised. Fig. 15
represents the external surface of Fig. 12, the apperture u being made in it for
the purpose of seeing the divisions on the brass scale which slides behind it,
and the line u serves as an index or point of coincidence to read off the
divisions on the scale. In this Fig. the holes is the place for the front point
of the pinion Fig. 18 to pass thro' and receive the milled head upon it, which
for that purpose is squared at its end. Fig. 19 represents the brass scale;
the position of it is seen in Fig. 21, the divisions appearing through the
aperture of the brass piece at u. Fig. 21 is a perspective representation of
the instrument put together and ready to be placed on two bearing surfaces
fixed upon any kind of ornamental stand, at the option of the person who
possesses it. I shall here observe, that the same letters of reference which have
been used to the other Figures are applied to the parts of the instrument in-
its complete state, wherever they can be seen. Fig. 20 represents the shape
of the two tubes united, with the position of the bulb at each end. The large
tube is hermetically sealed at the end w, while the bulb x, terminating by the
small cone y, has a small aperture thro' its apex left open for the purpose of
filling the tubes, and likewise for permitting the entrance of the atmosphere
upon the mercury inclosed in the tubes. Fig. 22 represents an edge view of
the scale, shewing its thickness. There is no scale necessary, as the Figures
are drawn to the real size of the instrument.
I shall now explain my method of filling balance thermometers. Now, I
do not claim the Invention of filling thermometers by the means hereafter
explained; I merely mention it as being a convenient method of filling balance
thermometers.
First, I immerse the bulb in a sufficient quantity of alchohal contained
in any convenient cup or vessel, and place the tube or tubes with the bulb
so immersed under the receiver of an air pump; I then pump the air out of
the receiver, by which means the air will be also extracted from the tubes;
I then let the air return into the receiver, the pressure of which will force the
alcohal into the tubes thro' the aperture y. If the tubes are not then sufficiently
full I repeat the operation, and when they are quite full I take them from

page_text: under the receiver and lay them horizontally in a tin trough, keeping tho
aperture of the bulb a. uppermost. I then pour water, which has previously
been heated a few degrees higher than the highest degree of temperature that
I wish my thermometer to indicate, into the trough. When the tubes have
laid a sufficient time to require the temperature of the water in which they are
immersed, I take them out and apply the flame of a candle or lamp to the
bulb x, keeping the aperture y downwards. I continue the heat until the
alcohol is all forced out of the bulb & thro' the aperture y. I then place it
again in the water as before, taking care that the water be two or three
degrees warmer than the highest degree that my thermometer is intended to
indicate. If then the tube b and the bulb z be full of alcohol, and the tube A
and the bulb & be empty, that part of the operation is right, if not, I introduce
a little more alcohol, or take out a little, as the case may require. When this
is done I heat the bulb with the flame of a candle or lamp, so as to cause
the moisture left in the bulb to force out through the aperture y in ists state
of vapour. While the vapour is thus passing out I suddenly immerse the
bulb x into quicksilver; the vapour will then be condensed within the bulb,
and the pressure of the atmosphere will force in the quicksilver to fill the
vacuum. I then place it again in the water, the temperature of which being
now exactly the highest degree that I wish my thermometer to indicate, when,
if the whole of the glass be quite full it is right, otherwise more quicksilver
must be introduced; this done, I note the temperature of the water when the
tubes and bulbs are quite full. I then wipe the glass dry, and fasten it
between the clamping pieces, which are to embrace it at about equal distances
from each end. I then move the scale so that a mark near the end, as at B
on the scale, may coincide with u where the degrees are to be read off, then
heat the tubes by means of the flame of a candle until the bulb & be com
pletely full of quicksilver, and move the glass to the right or left, as occasion
may require (having previously slackened the screw a, a), to bring the
instrument to its centre of gravity. I also at this time adjust the instrument
to its true centre of gravity by means of the milled head placed in the mortice i,
which enables me to elevate and lower the clamps and tubes in the frame at
pleasure. The mark B on the scale will ever after indicate the highest
temperature that the instrument is capable of ascertaining. The candle is
then to be removed, and the instrument removed into as low a temperature as
convenient, so that it be not colder than the lowest degree of temperature
that the instrument is intended to ascertain. The scale is then to be moved
by turning the nut to the right or left, as occasion may require, until the
instrument assume a horizontal position. The temperature of the water and