CERTAIN IMPROVEMENTS IN BAROMETERS AND SYMPIESOMETERS
Year: 1840

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
CUMMINS, of Leadenhall Street, in the City of London, Chronometer Maker,
send greeting.
WHEREAS Her present Majesty Queen Victoria, by Her Letters Patent
under the Great Seal of the United Kingdom of Great Britain and Ireland,
bearing date at Westminster, the Second day of April now last past, did
give and grant unto me, the said Charles Cummins, Her especial licence,
full power; sole privilege and authority, that I, the said Charles Cummins,
my executors, administrators, and assigns, or such others as I, the said
Charles Cummins, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term of years therein expressed, should and lawfully might make,
use, exercise, and vend, within England, Wales, and the Town of Berwick-
upon-Tweed, my Invention of "CERTAIN IMPROVEMENTS IN BAROMETERS AND
SYMPIESOMETERS;" in which said Letters Patent there is contained a proviso
obliging me, the said Charles Cummins, by an instrument in writing under
my hand and seal, particularly to describe and ascertain the nature of my said
Invention, and in what manner the same is to be performed, and to cause
the same to be enrolled in Her said Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said
Letters Patent, as in and by the same, reference being thereunto had, will
more fully appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Charles Cummins, do hereby declare that the nature of my said Invention of
Certain Improvements in Barometers and Sympiesometers, and the manner
in which the same is to be performed, is particularly described and ascertained

page_text: as follows, reference being had to the Drawings hereunto annexed, in all of
which similar parts are marked with the same letters :-
Fig. 1 represents part of a barometer, in order to exhibit one of my
improvements of a registering barometer. A, A, is the barometer tube, the
upper part of which is hermetically sealed in the usual manner, and protected
by a brass cap B. The lower end of the barometer tube A, A, fits into a
cistern or bag likewise in the usual manner, and therefore omitted in the
Drawing. C, C, represents the column of mercury, on the surface of which
at D floats a hardened steel magnet. E is a lever (seen also in Fig. 2, which
is a bird's-eye view of Fig 1 without the cap B) moving freely on its centre
F. G is a light socket made of iron or steel; it is held close to the barometer
tube A, A, by the portion H, while its opposite side is connected to the lever
E by a jointed rod or wire sliding freely within the latter. The socket G
is furnished with a black-lead pencil or marked I, the end or point being
pressed against the paper or card J, J, J, by means of a delicate spiral spring
acting against a small wire made like the well-known ever-pointed pencil.
K is a counterpoise weight made to balance the weight of the lever with its
socket and pencil, and thus allow the socket to move freely up and down the
barometer tube A, A. The paper or card J. J, J, is attached to a plate or
cylinder connected to a timepiece by fit and proper wheelwork, in such a manner
that an uniform motion is given to the paper or card J, J, J, from right to left.
This paper is divided by vertical lines, being placed at equal distances apart, to
indicate the quantity it moves in a given time. The spaces between the lines
may be of any suitable width, and may be made to indicate hours, days, &c.
In the Drawing I have assumed that each space indicates the motion of
twenty-four hours or one whole day. The entire paper is intended to register
thirty-one days or one month, but only the first nineteen days are exhibited in
the Drawing. The paper or card J, J, J, is divided into inches and tenths by
a series of horizontal lines, to denote the height of the mercury.
The action of this my first improvement on barometers is as follows:-
Whenever a change in the pressure of the atmosphere takes place, the mercury
rises or falls in the barometer tube A, A, and along with it the magnet, which,
attracting the socket, follows the motion of the magnet, while the pencil point
marks the paper or card J, J, J, and thus is registered the state of the baro-
meter at the time indicated by the figures representing the days of the month
placed along the top of the paper or card J, J, J, proper allowance being made
for the difference of specific gravity of the iron or steel magnet and mercury.
Another of my improvements in barometers is shewn at Figs. 3 and 4, in
which A, A, represents part of a barometer tube similar to that drawn in

page_text: Fig. 1, with a magnet D within it, and on the outside slides a socket G, with
a pencil I, sustained in its place by a counterweight L passing over the
pulley M. By this contrivance I am enabled to dispense with the lever E,
shewn in Figs. 1 and 2. The action of this modification of my registering
barometer, Figs. 3 and 4, is similar to that described in Figs. 1 and 2,
excepting that the counterweight L is raised or depressed with the socket G,
instead of the lever E.
Another of my improvements in barometers is, a method by which I am
enabled to compensate for the variation in the height of mercury in the
cistern occasioned by a change of pressure of the atmosphere altering the
height of the column of mercury in the barometer tube. The means by which
I accomplish this purpose is seen at Fig. 5, where A, A, is the lower part of a
fixed barometer tube; Y, Y, is a sliding cistern, containing the mercury,
which latter floats in a vessel of mercury Z, Z. The action of this contrivance
is as follows: When the mercury descends in the fixed tube A, A, it rises
in the cistern Y, Y, which, being thereby increased in weight, descends into
the vessel Z, Z, so that the surface of the mercury in the cistern Y, Y, remains
nearly at the same height around the fixed tube A, A, as before.
Figs. 6 and 7 represent my improvements in sympiesometers. Figure 6 is
a view of a sympiesometer tube unmounted, and Fig 7 another fitted up with
scales in the usual manner, to which I apply a vernier. The bulk N and
upper part of the tube O I fill with hydrogen gas in the usual manner, while
the lower portion P is filled with sulphuric acid or almond oil, as indicated by
the red color in Fig. 7. The upper part of the leg Q of the tube is bent
downwards at R, and the open end S is inserted into a glass tube, which is
shewn separately at Fig. 8, and the whole covered with a brass shield T, T, to
protect them, as seen at Fig. 7. U, U, is the fixt scale, which is divided so
as to indicate the compensation to be made in consequence of the expansion
occasioned by change of temperature. V is an index attached to the move-
able sliding scale W, W. X, X, is a vernier which slides upon the moveable
scale W, W, in the usual manner of barometers. The action and method of
observing with this instrument is as follows:-First, note the temperature by
the thermometer usually attached to the sympiesometer, which, for example, I
will suppose stands at sixty degrees of Fahrenheit; then slide the moveable
scale W, W, until the index V points to 60° degrees on the fixt scale U, U,
as seen in the Drawing Fig. 7. The height of the colored fluid in the tube
O, P, will thus represent the height of the mercury in a barometer at
that time and elevation, and is to be "read off" in the usual way by the
vernier X, X.

page_text: I do not mean or intend to claim as my Invention any of the parts herein-
before described, or that are shewn in the Drawing, which are known or
in use, but which it was necessary to describe and draw for the full and clear
understanding of my Invention; nor do I limit or confine myself to the
particular modifications described and shewn. But I do claim as my Inven-
tion of "Certain Improvements in Barometers and Sympiesometers,-
First, a method of registering by a barometer the pressure of the atmo-
sphere, as indicated by the height of a column of mercury, by means of a
magnet floating thereon and acting upon an iron or steel socket G, H, as
seen in the Drawings Figs. 1, 2, 3, and 4, whether such socket be made in
the manner therein shewn or by any other fit and proper contrivance for
that purpose.
Secondly, I claim a method by which a compensation is obtained, so that
the surface of the mercury in the cistern of a barometer remains nearly at the
same elevation, whatever be the changes in the atmospheric pressure, a
contrivance for which purpose is shewn at Fig. 5.
Thirdly, I claim as my improvements in sympiesometers such form of the
open end of the tube N, O, P, Q, R, S, as shall not compel me to employ a
cistern, as in the usual manner. An example of one new form for this purpose
is shewn at Q, R, S, Figs. 6 and 7.
Fourthly, I claim the employment of sulphuric acid (whether concentrated
or diluted) instead of almond oil as an enclosing fluid for filling of sympieso-
meter tubes.
In witness whereof, I, the said Charles Cummins, have hereunto set
my hand and seal, this Second day of October, in the year of our
Lord One thousand eight hundred and forty.