IMPROVE- MENTS IN APPARATUS FOR THERMOMETRIC, HYGROMETRIC, AND BAROMETRIC PURPOSES
Year: 1857

page_text: LETTERS PATENT to George Cumming, of Edinburgh, in the County of
Mid Lothian, North Britain, Gentleman, for the Invention of "IMPROVE-
MENTS IN APPARATUS FOR THERMOMETRIC, HYGROMETRIC, AND BAROMETRIC
PURPOSES."
Sealed the 9th February 1858, and dated the 29th August 1857.
PROVISIONAL SPECIFICATION left by the said George Cumming at
the Office of the Commissioners of Patents, with his Petition, on the
29th August 1857.
I, GEORGE CUMMING, of Edinburgh, in the County of Mid Lothian, North
Britain, Gentleman, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN APPARATUS FOR THERMOMETRIC, HYGROMETRIC, AND BAROMETRIC
PURPOSES," to be as follows, that is to say:-
This Invention relates to the arrangement and construction of a hygrometric
barometer or compound instrument for meteorological purposes, effecting all
the functions of a thermometer, hygrometer, and barometer, and enabling the
operator or user to take other observations, more or less connected with the
direct offices of these instruments. The motive power of this new apparatus
is derived from aqueous vapours or a compound of air, heat, and moisture.
It essentially consists of a cylindrical glass tube, of from twenty to thirty
inches in length, and from a half to three-quarters of an inch in diameter.
The top of the tube is mounted with a brass cap, into which a stop-cock.

page_text: (furnished with an ivory or silver mouthpiece) is screwed perfectly air-tight.
The bottom of the tube is cemented into a brass socket calculated to receive a
screw plug for supporting in a central position a standard thermometer at a
given height opposite to the neutral point of the barometrical scale engraved
upon the body of the instrument; the screw plug, moreover, contains a self-
acting valve for facilitating graduation. But when the instrument is to be
employed for permanent use, as, for instance, as a marine barometer, the tube
must be sealed at the top with a blow pipe, in order, as much as possible, to
guard against the chance of error; and this modification involves but little
extra trouble compared with the advantage gained. The standard thermometer
is to be placed in water or other fluid, and an efficient cistern is readily
obtained by sealing the bottom of the strong cylindrical two-inch glass case
required for protection as well as for giving unity to the indications of the
instrument; and all that is now required to complete it, is to have the case
cemented into a massive metallic socket, so as to serve as a pedestal, and
lastly, surmounted with a brass cap or cover, furnished with a lock and key to
prevent the possibility of tampering with the indications of the instrument, as a
united thermometer, hygrometer, and barometer. The fluid best suited for
organizing the instrument is water tinged with sulphate of copper, due care
being taken to guard against the effects of a low temperature.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Cumming in the Great Seal Patent Office on the
26th February 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
CUMMING, of Edinburgh, in the County of Mid Lothian, North Britain,
Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-ninth day of August, in the year of our Lord
One thousand eight hundred and fifty-seven, in the twenty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,,
the said George Cumming, Her special license that I, the said George
Cumming, my executors, administrators, and assigns, or such others as I, the
said George Cumming, 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 therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,

page_text: the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
APPARATUS FOR THERMOMETRIC, HYGROMETRIC, AND BAROMETRIC PURPOSES," upon
the condition (amongst others) that I, the said George Cumming, by an
instrument in writing under my hand and seal, should particularly 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 I, the said George Cumming, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the accompanying Drawings, and to the
letters and figures marked thereon, that is to say:
It
My said Invention relates to the arrangement and construction of a hygrome-
tric barometer, or compound instrument for meteorological purposes, effecting
all the functions of a thermometer, hygrometer, and barometer, and enabling
the operator or user to take other observations more or less connected with the
direct offices of these instruments. The motive power of this new apparatus
is derived from aqueous vapour, or a compound of air, heat, and moisture.
essentially consists of a cylindrical glass tube, of from twenty to thirty inches
in length, and from a half to three-quarters of an inch in diameter. The top
of the tube is mounted with a brass cap, into which a stop-cock (furnished
with an ivory or silver mouthpiece) is screwed perfectly air-tight. The bottom
of the tube is cemented into a brass socket, calculated to receive a screw plug,
for supporting in a central position a standard thermometer at a given height
opposite to the neutral point of the barometrical scale engraved upon the
body of the instrument. The screw plug, moreover, contains a self-acting
valve for facilitating graduation. But when the instrument is to be employed
for permanent use, as, for instance, as a marine barometer, the tube must be
sealed at the top with a blow pipe, in order, as much as possible, to guard
against the chance of error; and this modification involves but little extra
trouble compared with the advantage gained. The standard thermometer is
to be placed in water or other fluid, and an efficient cistern is readily obtained
by sealing the bottom of the strong cylindrical two-inch-glass case required for
protection, as well as for giving unity to the indications of the instrument;
and all that is now required to complete it, is to have the case cemented into
a massive metallic socket, so as to serve as a pedestal, and, lastly, surmounted
with a a brass cap or cover furnished with a lock and key, to prevent the
possibility of tampering with the indications of the instrument as a united

page_text: thermometer, hygrometer, and barometer. The fluid best suited for organizing
the instrument is water tinged with sulphate of copper, due care being taken
to guard against the effects of a low temperature.
And in order that my said Invention may be properly understood I shall
now proceed to describe the several illustrative Figures on the explanatory
Sheet of Drawings which I have hereunto appended, for the purpose of
showing certain modifications under which my improvements may be judi-
ciously carried out in practice. In my illustrative Drawing, Figure is a
partially sectional elevation of one modification of my improved hygrometrical
manometer, or instrument for measuring, by the elastic force of a volume of
confined air saturated with moisture, the variations in the pressure or density
of the atmosphere. Where the instrument is to be stationary and used for
observations upon land, it is preferred to fit it to a pedestal base or foot piece
A; this may be made of metal or wood, according to the style in which the
instrument is to be fitted up. The base must, however, be sufficiently heavy
'to ensure the steadiness of the instrument. To the upper part of the base a
short tubular socket B is attached by means of a screw and nut or other
attachment. Within the socket B, is fitted a glass tube C, the lower end of
which is sealed; the tube may be fastened into the socket with marine glue or
other cement, or be firmly imbedded in some yielding material, to prevent the
tube from fracture, when suddenly moved. The tube C, which forms a cistern
to contain the fluid with which the instrument is worked or organized, is
preferred to be from fifteen to thirty inches in length more or less, and of about
two inches in diameter. To the upper extremity of the cistern C, is adapted
a brass collar D, to which a cap E, is screwed, thus enclosing the internal
parts of the instrument to protect them from injury, or from being tampered
with.
Within the cistern C is suspended a second glass tube F; this tube
may vary from twelve to twenty-six inches in length, and from one-half to
three-quarters of an inch in diameter. The upper extremity of the tube F,
is sealed by the blow-pipe and cemented into a brass cap G, the upper part of
which is hollowed out to form a socket for the ball H. From the centre of
the ball H, a screw I, of about four inches in length projects upwards; this
screw passes through the plate J, and is secured thereto by the milled edged
nut K. The tube F is suspended within the cistern C, by the plate J, which
rests upon the edge of the collar D, and in this manner the tube F, by means
of its ball and socket joint, swings freely in the cistern C. The plate J has
upon its periphery two small projections, which fit into corresponding notches
cut in the collar D, this arrangement prevents the plate from turning
round when once placed in its proper position. By means of the nut K,

page_text: which works on the screw I, the tube F may be raised or lowered in the.
cistern C, as required. The cap E is locked to the instrument by means
of a short spindle L, which passes through a tube projecting downwards from
the cap E; the spindle L is made with an external screw that fits a corre-
sponding screw in the tube. The lower end of the spindle L'fits into a hole
made for the purpose in the plate J; and the upper end of the spindle is.
squared to receive a box ended key M, by means of which the spindle L is.
screwed up or down, and thereby lock or unlock the cap E. The lower end.
of the tube F is cemented or otherwise fastened into a socket N, into which
a metal plug O is screwed: the upper part of the plug is made with an
external screw, to connect it with the tube P. The upper portion of the plug
O, is hollowed out to form a small chamber or conical valve seat; the bottom
of the recess terminates in a tubular passage extending downwards through
the plug. A triangularly shaped piece of metal or wire is passed through the
tubular passage in the plug, on which is screwed a conically or other shaped
valve Q, which fits accurately to the valve seat in the plug O. To the lower
extremity of the valve stem is attached a hollow metal float R, the buoyancy
of which serves to raise the valve Q, and thereby open a communication
between the cistern C, and the tube F, when the former is partially filled
with fluid. The bulb of a standard thermometer S is inserted into the
upper part of the tube P, and fastened firmly therein by means of marine
glue or other suitable cement; the bulb of the thermometer may, if necessary,
rest upon a plug of cork or other support fitted into the tube P. A small
hole T is made through the tube P, immediately under the thermometer bulb,
which allows the liquid in the cistern to pass from the tube P into the tube.
F, and thus form a communication between the barometric tube F and the
cistern C. The stem of the thermometer is engraved and graduated into
degrees in the ordinary manner, and a portion of the tube F is divided into
inches and tenths of the same, corresponding to the ordinary barometric scale,
and figured in accordance therewith, that is to say, from twenty-seven to thirty-.
one inches. The fluid made use of to organize this instrument is, by preference,
water, slightly coloured for the convenience of observation. Prior to adjusting
the instrument for use a quantity of the coloured fluid is poured into the cistern
C, until it reaches a height of about four inches more or less. The plug O is
now to be unscrewed from the tube F, and a sufficient quantity of the coloured
water poured therein to stand to the height of six inches when inverted.
plug O is replaced and the tube rapidly inverted, so that the valve may close
without allowing the fluid to escape; the height of the fluid is now regulated
by careful manipulation, as to stand at twenty-nine inches on the barometric
The

page_text: scale. The tube F, with the enclosed thermometer, is now to be lowered into
the cistern and its height carefully adjusted, so that the level of the fluid both
in the cistern and the barometric tube stands at twenty-nine inches of the
barometric scale.
In making these adjustments it is also preferred that the thermometer is so
arranged that the sixtieth degree of its scale likewise stands at the same level,
namely, the line indicating twenty-nine inches. The immersion of the lower
end of the tube F in the cistern C causes the metal float R to raise the float
R, which carries the valve Q; the tinged water consequently flows up through
the plug O and through the hole in the tube P into the tube F. When the
water stands at a level in both the cistern and the barometric tube F, a mark
should be made upon the exterior of the tube C, to indicate its height, so that'
a small quantity of the tinged water may be added from time to time to supply
loss by evaporation; this loss will however be very small. The instrument.
being thus adjusted, the volume of air above the water in the cistern C, and
to which the external air has access, is acting by its elastic force against the
volume of aqueous vapour confined within the barometric tube F. Any vari-
ation in the pressure or density of the atmosphere is indicated by the rising or
falling of the column of liquid in the barometric tube F, the height of the
barometric column and the temperature, as indicated by the thermometer, being
read off simultaneously. By means of a short arithmetical operation, the
bygrometrical condition of the atmosphere 'is also readily obtained for each
degree of temperature. Ninety degrees are taken as an equivalent for dry atmo-
spheric air, and sixty degrees for 'air moist to saturation, the mean of the two
numbers being seventy-five. Ninety is used as a constant number in reducing
observations to obtain the dew point. Thus, if the temperature of the air is
sixty degrees, this number added to 'ninety equals one hundred and fifty, the
mean of which is seventy-five, from which subtract sixty, leaving fifteen;
divide the fifteen by two, the quotient is seven and five-tenths; this being sub-
tracted from sixty, gives fifty-two and five-tenths as the dew point. If the
temperature is seventy, this added to ninety is one hundred and sixty, divided
by two, leaves eighty; subtract seventy and divide the quotient ten by two,
which leaves five, and this number being subtracted from seventy leaves sixty-
five as the dew point. In this manner all the higher and lower numbers of
the thermometric scale may be reduced, and the instrument thus becomes, in
addition to its other qualifications, a first class hygrometer. In fitting the
instrument up for use upon land, the ball and socket joint may be dispensed
with, and in lieu thereof the cap of the barometric tube F may terminate in a
tube having at its upper extremity a stop-cock. The exterior of this tubular

page_text: passage has a screw thread cut upon it to which a nut is fitted, so that the
barometric tube may be adjusted as to height. It is preferred to make the
stop-cock with an ivory or silver mouthpiece, so that upon opening the stop-
cock the lips may be applied to the mouthpiece and the coloured fluid drawn
up into the barometric tube F; the stop-cock is then shut and the fluid
allowed to find a level. The adaptation of the stop-cock affords great facility
in adjusting the height of the fluid within the barometric tube of instruments
constructed for observations upon land; the valve of the barometric tube being
opened either by the float resting upon the bottom of the cistern or by its
buoyancy in the liquid.
In arranging this instrument for use as a substitute for the ordinary marine
barometer, the instrument must have the ball and socket fitting at the upper
extremity of the barometric tube; the foot A and the socket B are dispensed
with, the instrument being hung up by a hook on the cap E. In the arrange-
ment of my improved marine barometer I prefer the barometric scale. being
engraved upon a metallic tube which surrounds the barometric tube. A
portion of this tube is cut away to the extent of the rise and fall of the
barometric column, the scale being engraved in the usual manner upon the
margin of the opening, so that any variation in the height of the column may
be readily observed and accurately measured. This tube is raised and de-
pressed by means of a nut and screw at its upper extremity; by this means,
the tube is readily made to follow the variations in the height of the barometric
column, and being set from time to time to the level of the fluid, the slightest
variation in the pressure and density of the atmosphere is instantly indicated.
The thermometer may be conveniently arranged in front of and at the upper
part of this barometric scale tube. The mode of charging the instrument
with the coloured fluid and of adjusting its height is the same as in the modi-
fication first berein described. In order to shorten the barometric instrument
and thereby render it more portable and convenient in other respects, I bend
the tube to half its length, more or less.
This modification of my hygrometrical manometer is shown in Figure 2 of
my illustrative Drawing. It consists of a glass tube U sealed at both ends;
the tube is bent so as to form two parallel legs V and W, extending upwards,
and about two inches asunder. At the centre of the horizontal portion U of
the tube, an aperture is made by means of a blow pipe, and to this opening a
central leg X is joined thereto by the blow pipe; the upper extremity of this
central leg is open. The three-legged siphonic instrument thus formed is
secured to a piece of wood Y, by thin brass bands and screws. The piece of
wood has a groove cut in it at the back of the central leg X of the siphon; the

page_text: groove is fitted with a corresponding piece of wood Z, moveable therein, and to
which is attached a barometric scale a. The sliding piece of wood Z carrying.
the scale is moved up and down by means of a rack and pinion b, or an
equivalent therefor; the barometrio scale is figured from the lowest number
downwards to the highest. A thermometer c is inserted in the central leg X,
the bulb of which rests upon a plug or cork or other material, so arranged as
not to interfere with the passage of the liquid with which the vessel is charged.
Or instead of this arrangement, the glass tube may be slightly contracted to
form a rest. for, the bulb. Or the thermometer may be secured to the
wooden back Y of the instrument, and arranged parallel to one of the;
lateral legs V or W... The wooden back Y of the instrument is fitted into a
foot, and the whole protected by a wide class tube or shade d. The instrument
is charged by. pouring tinged water into the central leg X, until its level,
reaches the sixtieth degree on the thermometer enclosed therein; the
extremity of the central stem may then be closed by a cap or plug not air-
tight, but, capable of being made so for the convenience of travelling. As the,
density of the external air increases, the fluid in the central column descends,
whilst it rises in the two lateral legs V and W, the increase of pressure being
marked by the liquid reaching a higher division of the barometric scale.
On the contrary, when the elastic force of the atmosphere decreases, the
rising of the liquid column in the central leg indicates a lower number on the
barometric scale agreeable to the laws of the elastic force of confined aqueous.
vapour at different temperatures. This modification of the instrument is
applicable to all the purposes of, the first herein-before described. By means
of these instruments, meteorological observations may be made with great ease
and facility, and without the disadvantages inseparable from the construction
of the mercurial barometer.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried
into effect, I may observe in conclusion that I do not confine or restrict.
myself to the precise details or arrangements which I have had occasion to
describe or refer to, as many variations may be made therefrom, without
deviating from the principles or main features of my Invention; but what I
consider to be novel and original and therefore claim as the Invention secured
to me by the herein-before in part recited Letters Patent, is, -
First, the general arrangement and construction of instruments for indicating
variations in the pressure or density of the atmosphere as herein-before
described.
Second, the system or mode of indicating variations in the pressure of the

page_text: atmosphere, by means of the elastic force of aqueous vapour, or air saturated
with moisture as herein-before described.
Third, the system or mode of combining thermometric and barometric
instruments in one, and of obtaining therefrom indications of the hygrometrical
condition of the atmosphere, as herein-before described.
In witness whereof, I, the said George Cumming, have hereunto set my
hand and seal, this Twenty-third day of February, in the year of our
Lord One thousand eight hundred and fifty-eight.
GEO. CUMMING. (L.S.)