Improvements in Barometers.
Year: 1886

page_text: Date of Application, 15th Mar., 1886.
Complete Left, 15th Dec., 1886.
Complete Accepted. 4th Mar., 1887.
PROVISIONAL SPECIFICATION.
Improvements in Barometers.
I, SAMUEL AUGUSTINE DE NORMANVILLE of 26 Gloucester Road, Kensington, in
the county of Middlesex, Gentleman, do hereby declare the nature of this Invention
to be as follows:-
My improvement consists in a modification of the form of barometer known as
the sympicsometer, whereby the two corresponding scales for correction for temperature
are dispensed with and the necessity for setting the instrument for this correction
before reading consequently avoided. My improved instrument consists essentially of
the following arrangement. A glass tube open at top and terminating below in a
closed bulb, preferably turned up, is affixed vertically on a frame. The said tube and
bulb are partly filled with sulphuric acid, or other suitable liquid, while the remainder
or upper part of the bulb contains air or other suitable gas.
A slip or frame is provided to slide vertically upon the aforesaid frame and parallel
to the aforesaid glass tube.
Upon such slip or frame, a thermometer, preferably of a sensitive nature, is fixed in
the usual vertical position.
The thermometer and frame may be actuated by a rack and pinion or other suitable
means. Thus I sometimes provide grooves for the thermometer frame to slide in, and
actuate the said frame by means of an india rubber roller on a spindle, the friction of
the roller being sufficient to move the frame and to retain it in any position. On the
thermometer frame, or attached to it, is figured a portion of the barometrical scale,
say from 28 to 31 inches, the spaces being not necessarily inches, but in proportion to
the range of the instrument as afterwards described.
Against this scale but attached to the main frame is placed a fixed pointer or index.
The air space in the aforesaid bulb is so adjusted that the rise or fall of the liquid in
the tube for any variation of temperature is equal to the rise or fall of the mercury or
spirit in the thermometer for the same variation of temperature. Then if the upper
surfaces of the fluids in the two tubes are brought level with each other (by means of
the aforesaid sliding movement) the two fluids will always move pari passu under all
changes of temperature, and will always remain level together as far as changes of
temperature only are concerned..

page_text: The two fluids heing level the index is in the first instance moved into such a
position as to give the same reading as a good standard Barometer, and is then per-
manently fixed in such position. As long as the barometrical pressure remains
unchanged, the two fluids will still remain level with each other, no matter what.
changes of temperature take place, but when any variation in pressure occurs the
fluids will be out of level with each other. A fresh reading is then obtained by
bringing them again into level by means of the sliding movement, the barometrical
scale being thereby moved a corresponding amount against its fixed index, and the
observation remains recorded without further trouble.
It is obvious that the whole arrangement may if desired be inverted, the air bulb
being at top, as in the sympiesometer as usually made, and the thermometer inverted
to correspond, or it may be made with the tubes horizontal, or bent into a circular
form, or otherwise modified in various ways without affecting the principle.
The size of air bulb necessary to correspond with any given thermometer may be
obtained by measurement and calculation according to the calibre of tube used, the
formula for expansion of air being well known, and the final adjustment is made by
testing at different temperatures with the corresponding thermometer and increasing
or lessening the air space by putting more or less fluid into the bulb as required.
In practice the barometrical scale will be sufficiently correctly spaced by allowing a
distance equal to 17 degrees Fahrenheit, of the thermometer used, for each "inch "
of the scale, or the scale may be divided by comparison with a standard instrument.
If desired an ordinary thermométrical scale may also be added to the instrument.
I, SAMUEL AUGUSTINE DE NORMANVILLE of 26 Gloucester Road, Kensington, in the
county of Middlesex, Gentleman do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
My improvement consists in a modification of the form of barometer known as the
"Sympiesometer," whereby the two corresponding scales for correction for tempera-
ture are dispensed with, and the necessity for setting the instrument for this correction
before reading, consequently avoided. My-improved. instrument consists essentially
of the arrangement shewn in the accompanying sheet of drawings, in which Fig. Tis
a front elevation, and figure 2 is a cross section through the line X X in Fig. 1, of a
barometer constructed according to my invention, Fig. 3 is a front elevation and
Fig. 4 is a cross section through the line YY on Fig. 3, of a similar instrument of
somewhat modified form. The same letters of reference denote similar parts through-
out the figures. A glass tube A open at the top A¹ and terminating below in a closed
bulb A, preferably turned up as shewn, is fixed vertically on a frame B. The said
tube and bulb are partly filled with sulphuric acid or other suitable liquid, as indicated

page_text: A
by the darkened part of the tube, while the remainder or upper part of the bulb
contains air or other suitable gas; such a tube containing an elastic cushion of air or
gas and an indicating column of liquid is commonly known as a
* manometer."
slip or frame is provided to slide vertically upon the aforesaid frame B and parallel
to the aforesaid glass tube A. Upon such slip or frame a thermometer D, preferably
of a sensitive nature, is fixed in the usual vertical position. The thermometer D and
frame may be actuated by a rack and pinion or other suitable means. Thus, as
shewn in Fig. 2, I sometimes provide grooves E E for the thermometer frame to.
slide in, and actuate the said frame by means of an indian rubber roller F on a
spindle F, provided with a milled head F2; the friction and elastic pressure of the
roller being sufficient to move the frame and to retain it in any position. On the thermo-
meter frame C, or attached to it, is figured a portion of the barometrical scale say from
28 to 31 inches as shewn, the spaces being not necessarily inches, but in proportion to
the range of the instrument as afterwards explained. Against this scale, but attached
to the main frame B, is placed a fixed pointer or index H; the air space in the
aforesaid bulb A2 is so adjusted that the rise or fall of the liquid in the tube A for any
variation of temperature is equal to the rise or fall of the mercury or spirit in the
thermometer D for the same variation of temperature.. Then if the upper surfaces of
the liquids in the two tubes are brought level with each other (by means of the afore-
said sliding movement) the two liquids will always move pari passu under all changes
of temperature, & will always remain level together as far as changes of temperature
only are concerned. The two fluids being level, the index H, is, in the first instance,
moved into such a position as to give the same reading as a good standard barometer
and is then permanently fixed in such position. As long as the barometrical pressure
remains unchanged, the two liquids will still remain level with each other, no matter
what changes of temperature take place, but when any variation in pressure occurs.
the liquids will be out of level with each other; a fresh reading is then obtained by
bringing them again into level by means of the aforesaid sliding movement, the
barometrical scale on C being thereby moved a corresponding amount against its fixed
index H, and the observation remains recorded without further trouble. It is obvious
that the whole arrangement may if desired be inverted, the air bulb A2 being at top,
as in the sympiesometer, as usually made, and the thermometer D inverted to corre-
spond, or it may be made with the tubes horizontal, or bent into a circular form or
otherwise modified in various ways without affecting the principle on which the
instrument is constructed. In the circular form, shewn in Figs. 3 and 4, the parts
correspond with those shewn in Figs. 1 and 2, but instead of the scale C, and
thermometer D, sliding vertically for adjustment, they are caused to rotate about a
centre C to effect the same purpose; a rubber roller or a pinion and curved rack, or
other suitable device being employed to give the required motion. It is obvious that
this form of instrument must be so adjusted that the two liquids move the same
angular distance for variations of temperature, and not the same actual distance (as in
the vertical form of instrument) and the reading taken by bringing the two liquid
surfaces on to the same radial line. The bulb A², of the tube A, containing the air, is
preferably placed behind the rotating scale Cas indicated by dotted lines in Fig. 3,
and in cross section in Fig. 4. In place of using a quantity of acid in the tube A, as
shewn in figures 1 and 2, only a few drops of acid may be employed occupying a short
space in the tube & leaving the bulb empty, (i.e. what may be called "a bubble"
acid) this will practically eliminate the influence of gravity, which necessarily affects
the solid column of liquid and in this case the bulb A need not be turned up, while
the exact capacity of the bulb may be obtained, either by blowing in a flame, or by
reducing a bulb of too large dimensions by placing some acid in it. This arrangement
is particularly applicable to the circular form of instrument, in which retardation and
acceleration, due to the action of gravity, would alternately take place on opposite
sides of the curve, if a solid column were used. The open end A¹, of the tube A, as
shewn in Fig. 1 may be prolonged and turned down to the bottom of the frame B, to
afford security against an escape of acid in case of extreme rise of temperature, and to
remove the acid surface further from the outer air and so tend to check absorption of
of

page_text: moisture. If preferred the index H may be on the sliding or rotating frame C, and
the scale be marked on the frame B. The size of air bulb necessary to correspond
with any given thermometer may be obtained by measurement and calculation
according to the calibre of the tube A used, the formula for expansion of air being
well known, and the effect of gravity being of course, where necessary, allowed for,
and the final adjustment is made by testing at different temperatures with the corre-
sponding thermometer and increasing or lessening the quantity of air contained in the
bulb A, by putting more or less fluid into the bulb as required. In a cheap
instrument, where extreme accuracy is not requisite, it will be sufficient, in dividing
the scale, to allow a space equal to 174 deg. Fahr. of the particular thermometer used,
for cach "inch" of the barometer, or say 18 degrees for the inch from 28 to 29 inches,
17 degrees for 29 to 30 inches, and 1.6 degrees for 30 to 3.1 inches. As the expansion
of the acid itself really affects the question slightly, higher class instruments should
however be scaled by actual tests at different pressures (either natural or under the
air pump) in comparison with a standard barometer of known accuracy. If desired
an ordinary thermometrical scale may be added to the instrument. I wish it to be
understood that in the construction of my improved barometer, I do not necessarily
confine myself to the precise forms and arrangements of the various parts as herein
set forth, provided that in all cases the essential principles of my invention are
retained.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed I declare that what I claim is―
The improved construction of a barometer, consisting of the combination of a
"manometer" and thermometer adjusted to the same scale for variations of tein-
perature, so mounted as to permit of the direct comparison of their liquid surfaces,
and provided with a sliding or other suitable movement, relatively to each other, by
which movement such surfaces can be brought into correspondence, the act of so
bringing the said surfaces into correspondence controlling at the same time the
position of an index against a barometrical scale, substantially in the manner as herein
set forth, or any mere modification thereof.
AMBROSE MYALL, C.E.,
21, Cockspur Street, London, S. W.,
Agent for the Applicant.