IMPROVEMENTS IN BAROMETERS."
Year: 1875

page_text: LETTERS PATENT to Marie Leon Paul Hans, of Vincennes, Depart-
ment of the Seine, France, a Captain in the French Artillery, and
Hippolyte Alexandre Hyacinthe Hermary, of No. 43, Rue St.
Dominique, St. Germain, in the City of Paris, France, a Captain in
the French Artillery, for the Invention of "IMPROVEMENTS IN
BAROMETERS."
L
PROVISIONAL SPECIFICATION left by the said Marie Leon Paul
Hans and Hippolyte Alexandre Hyacinthe Hermary at the Office
of the Commissioners of Patents, with their Petition, on the
11th June 1875.
We, MARIE LEON PAUL HANS, of Vincennes, Department of the
Seine, France, a Captain in the French Artillery, and HIPPOLYTE
ALEXANDRE HYACINTHE HERMARY, of No. 43, Rue St. Dominique,
St. Germain, in the City of Paris, France, a Captain in the French
Artillery, do hereby declare the nature of the said Invention for "Im-
PROVEMENTS IN BAROMETERS," to be as follows:—
This Invention has for its object improvements in barometers,

page_text: Our barometer consists of two thermometers, the one an ordinary
liquid thermometer, and the other a gas thermometer.
The gas thermometer consists of a thermometer tube partly filled
with any gas which is kept in by a liquid index, one end of the tube
being open, so that the position of the index depends both on the tem-
perature and on the pressure of the atmosphere.
It has long been known that the pressure of the atmosphere could be
ascertained by calculation from the simultaneous readings of a liquid
and a gas thermometer. The object of our Invention is to so construct
an instrument that the pressure may be read off without calculation.
We fix the two thermometer tubes on a board horizontally and one
above the other, say the liquid one uppermost. Below the gas
thermometer we have a slide, this slide is so arranged that its direction
of motion is always in the straight line, passing through the absolute
zero (-273° C.) of the liquid thermometer and the absolute zero of the
gas thermometer, the thermometer tubes being assumed to be produced
in straight lines to their absolute zeros.
On the liquid thermometer there is a sliding index having attached
to it a cord which passes through a hole in the before-mentioned slide,
and hangs down across a graduated scale, being kept tight by a weight
fixed to its end.
To read the barometer, the index on the liquid thermometer is first
set to the temperature there shown, the lower slide is then moved until
the portion of the cord between the two slides passes over the end of the
liquid index in the gas thermometer, the pressure of the atmosphere is
then indicated by the place at which the lower portion of the cord
crosses the graduated scale. It will be found that this reading is
entirely independent of temperature and depends only on the pressure.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Marie Leon Paul Hans and Hippolyte Alexandre 30
Hyacinthe Hermary in the Great Seal Patent Office on the 10th
December 1875.

page_text: Captain in the French Artillery, and HIPPOLYTE ALEXANDRE HYACINTHE
HERMARY, of No. 43, Rue St. Dominique, Saint Germain, in the City of
Paris, France, a Captain in the French Artillery, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eleventh day of June, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said Marie Leon Paul Hans and Hippolyte
Alexandre Hyacinthe Hermary, Her special license that we, the said
Marie Leon Paul Hans and Hippolyte Alexandre Hyacinthe Hermary,
our executors, administrators, and assigns, or such others as we,
the said Marie Leon Paul Hans and Hippolyte Alexandre Hyacinthe
Hermary, our executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully
might make, use, cxercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man,
an Invention for "IMPROVEMENTS IN BAROMETERS," upon the condition
(amongst others) that we, the said Marie Leon Paul Hans and
Hippolyte Alexandre Hyacinthe Hermary, our executors or adminis-
trators, by an instrument in writing under our or their hands and
seals, or under the hand and seal of one of us or them, should par-
ticularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that we, the said Marie Leon Paul Hans and
Hippolyte Alexandre Hyacinthe Hermary, do hereby declare the nature
of the said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following
statement thereof, that is to say :—
This Invention has for its object improvements in barometers.
Our barometer consists of two thermometers, the one an ordinary
liquid thermometer, and the other a gas thermometer.
The gas thermometer consists of a thermometer tube partly filled with
any gas which is kept in by a liquid index, one end of the tube being

page_text: open, so that the position of the index depends both on the temperature
and on the pressure of the atmosphere.
It has long been known that the pressure of the atmosphere could be
ascertained by calculation from the simultaneous readings of a liquid
and a gas thermometer. The object of our Invention is to so construct
"an instrument that the pressure may be read off without calculation.
We fix the two thermometer tubes on a board horizontally and one
above the other, say the liquid one uppermost. Below the gas
thermometer we have a slide, this slide is so arranged that its direction
of motion is always in the straight line passing through the absolute
zero (-273° C.) of the liquid thermometer and the absolute zero of the
gas thermometer, the thermometer tubes being assumed to be produced
in straight lines to their absolute zeros.
On the liquid thermometer there is a sliding index having attached to
it a cord which passes through a hole in the before-mentioned slide and
hangs down across a graduated scale, being kept tight by a weight fixed
'to its end.
To read the barometer the index on the liquid thermometer is first
set to the temperature there shown, the lower slide is then moved until
the portion of the cord between the two slides passes over the end of the
liquid index in the gas thermometer; the pressure of the atmosphere is
then indicated by the place at which the lower portion of the cord
crosses the graduated scale. It will be found that this reading is
entirely independent of temperature, and depends only on the pressure.
In order that our Invention may be most fully understood and readily a
carried into effect, we will proceed to describe the Drawings hereunto
annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 shows a front view, and Figure 2 a back view of a barometer
constructed according to our Invention, and in the manner which we 3
prefer.
A is a liquid thermometer graduated according to the centigrade
scale; B is an air thermometer consisting of a glass tube bent back-
wards and forwards, as shown, and having the end b closed and the
end b' open to the air. At the bend ³ there is some concentrated 3
sulphuric acid colored with indigo or otherwise, and to prevent the

page_text: alteration of the acid some non-drying oil is put into the other bend 68
so that the acid is not exposed to the hydrometric influence of the air.
The colored acid thus constitutes the index of the air thermometer B
which is read at the point of contact between the liquid and the air
contained in the branch *. This branch is bent back so as to come
over the face of the board, whilst the other four branches are hidden at
the back. Arranged parallel to the thermometer A is a rod which
serves as a guide for a slider C carrying a pointer to indicate the
extremity of the liquid column in the thermometer similarly underneath
the air thermometer B, but inclined so as to follow a line which is that
of the absolute zeros a rod D is fixed along which a slider E works.
The slider carries an eye pierced with a hole for the free passage of a
thread, which at its upper end is attached to the upper slider C; these
sliders serve to direct the thread when an observation is, to be made
from the end of the column in the thermometer A. to the point of
contact of the acid with the air in the branch 6' of the air thermometer B.
The thread carries a small weight to make it pass vertically down the
lower part of the table, which is furnished, as shown, with a barometric
scale graduated according to the horizontal projection of graduations
(not shown) upon the oblique line of absolute zeros represented by the
rod D. This graduation of D is made by comparison or by a simple
formula H=760 × 273 × in which H is the pressure in millimetres;
t, the temperature; t', the number of degrees shown at the moment of
observation by the air thermometer, which will have been graduated
like an ordinary thermometer at a pressure of 760.
273 x t
The position of the thread at its intersection with the barometric scale
indicates the true atmospheric pressure.
It is unnecessary to say that we do not limit ourselves to the arrange-
ment shown in the Drawings, which may be modified in various ways to
adapt them to different applications of our Invention; we do not limit
ourselves to the employment of concentrated sulphuric acid, which may
be replaced by glycerine or other suitable liquid. The oil stopping may
be dispensed with, it is not required if a liquid which is not affected by
the air be employed as an index; the air thermometer may then be
reduced to a more simple construction. The sliders may work directly
upon the tubes of the instrument, and the indicating thread can be
replaced by a needle or other mechanical index, and there can be

page_text: arranged to slide along the line of absolute zeros or its horizontal
projection a moveable scale suitably divided, which is to be adjusted
according to the altitude of the place at which the observation is made;
nevertheless experience has lead us to prefer the mode of construction
above described.
The graduations of the thermometer and of the indicating scale can
be adapted to the system in use in different countries, but we claim as
our Invention,-
The construction, substantially as described, of an apparatus based
upon the principle that the pressure being constant the intersection of
a straight line passing through the absolute zeros of a liquid and air
thermometer with another straight line passing through the reading
points of the two thermometers will always be exactly the same what-
ever may be the temperature.
We also claim the use of oil, substantially in the manner described,
to protect the column of acid from the action of the air.
In witness whereof, we, the said Marie Leon Paul Hans and
Hippolyte Alexandre Hyacinthe Hermary, have hereunto set
our hands and seals, this Seventh day of December, in the year
of our Lord One thousand eight hundred and seventy-five.
A
LEON PAUL HANS.
(L.S.)
HIPPOLYTE ALEXANDRE HYACINTHE HERMARY. (L.S.)