IMPROVEMENTS IN THERMOMETRY AND IN APPARATUS USED THEREFOR
Year: 1884

page_text: I, GEORGE THOMAS BEILBY of Midcalder in the County of Midlothian, North
Britain, Fellow of the Chemical Society and Chemical Engineer, do hereby declare
the nature of the said invention for "IMPROVEMENTS IN THERMOMETRY AND IN
APPARATUS USED THEREFOR," to be as follows -
This Invention has for its object improvements in the measurement of
temperature especially at points above or below the range of the mercurial
thermometer. The apparatus consists of several principal parts.
(1) A bulb or expanding vessel filled with dry air or other suitable gas.
(2.) A measuring tube in which the air to be measured is cut off from the outer
air by a piston of mercury or other suitable material.
(3.) A connecting tube by which the air passes from the Bulb (1) to the
measuring tube (2) or vice versa. The cubic capacity of this tube (3) must be
inconsiderable compared with that of the bulb (1) and measuring tube (2).
(4) A jacket or casing surrounding the measuring tube (2), through which steam
of approximately constant pressure.is passed, or in which any medium is contained,
so that the tube (2) and its contained air are maintained at a constant known
temperature.
(5) An automatic pressure regulator in which the free end of the measuring
tube (2) is connected by means of another tube of small bore and of convenient
length, with a tube, which is hereinafter called a barometer tube, placed perpen-
dicularly and closed hermetically at its upper end. In this tube is a column of
nercury of sufficient height to give the desired pressure to the air within the
thermometer. The barometer tube is much longer than the contained column of
mercury, so that changes of volume occurring within the apparatus, cause the
column to move up or down in the tube without alteration of length and
consequently without alteration of pressure.
In place of an automatic pressure regulator an adjustable pressure regulator may
be employed.
The use of an automatic pressure regulator obviates the necessity for barometric
observations, such as would be needed if the free end of the measuring tube were
open to the atmosphere. When, however, a pressure regulator is not used, it is
advisable to have the scale of the thermometer moveable, so that its zero point
may be adjusted for the pressure of the atmosphere at the time of observation.
The action of my improved apparatus depends on the comparatively uniform
expansion by heat of air or other perfect gases under uniform pressure,

page_text: Hitherto no thermometer has come into ordinary use by which temperature
above the boiling point of mercury could be observed by mere inspection of
a moveable indicator. With this improved thermometer, temperatures up to
and beyond the softening point of glass can be observed as easily as lower
temperatures can now be with a mercury thermometer.
The action of the apparatus is as follows:
When the expanding vessel (1) is heated, the expansion of the contained air
causes a part of the said air to be expelled through the connecting tube (3) into
the measuring tube (2). The piston of mercury is driven forward in the tube, and
by suitable graduation the volume of the expelled air is measured by the position
of the piston. The cubic capacity of the connecting tube being comparatively
small, its variations of temperature may be neglected without seriously affecting
the accuracy of the observations.
The temperature and pressure of the air in the measuring tube are known and
constant, the expansion of the bulb itself can be calculated-it is therefore possible
to measure with any required accuracy the expansion of the original air in the
bulb under the influence of any unknown temperature, by measuring the volume
of the air in the measuring tube.
Thermometers of this construction may be graduated by measuring the capacities
of the bulb and of the measuring tube respectively, thereafter marking off on the
latter the volume corresponding with each temperature, using in these calculations
the coefficient for the expansion of air at constant pressures.
Certain fixed points of the scale may be determined by experiment as in the
graduation of mercurial thermometers, the graduation being completed by inter- and
extra-polation.
The expansion of the air in the bulb with increasing temperature causes a
decreasing amount to be expelled per degree, therefore the degrees as marked on
the measuring tube, diminish in length towards the higher end of the scale. To
facilitate the graduation of thermometers in whose expanding and measuring
vessels intentional or unintentional variations will occur, scales or diagrams are
prepared to which any thermometer can be readily referred, and from which it
can be graduated.
It is evident that the apparatus and system hereinbefore described can be applied
for the determination of low as well as of high temperatures.
Dated this twenty first day of February 1884
J. H. JOHNSON, DAY & JOHNSON,
Petitioner's Agents,
115, St. Vincent Street, Glasgow.

page_text: I, GEORGE THOMAS BEILBY, of Midcalder, in the County of Midlothian, North
Britain, Fellow of the Chemical Society and Chemical Engineer do hereby declaro
the nature of my said invention for IMPROVEMENTS IN THERMOMETRY AND IN
APPARATUS USED THEREFOR and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement:-
This Invention has for its object improvements in the measurement of tem-
perature, especially at points above or below the range of the mercurial
thermometer.
The apparatus for carrying out these improvements is represented upon the
annexed sheets of drawings of which Figure 1, is a section of a bulb and measuring
tube, and Figure 2, is a section of the same shewn on a reduced scale and connected
with its automatic pressure regulator. Figure 3, is a section corresponding to
Figure 1, of a thermometer wherein the barometer tube forms a straight con-
tinuation of the measuring tube as hereinafter set forth.-Figures 4, and 5.
represent the markings or graduation of two thermometers of varying sizes and
constructed according to my present Invention, and Figure 6, is a diagram
prepared from the same, shewing an example of the ratios of the various parts of
the scale from which a thermometer constructed according to my present Invention,
can be readily graduated.
The apparatus as shewn at Figures 1, and 2, consists of several principal parts.
First. The bulb or expanding vessel a, filled with dry air, or other suitable gas.
Secondly. The measuring tube b, in which the gas to be measured is cut off from
the outer air by the piston c, of mercury or other suitable material.
Thirdly. The connecting tube d, by which the gas passes from the bulb or
expanding vessel a, to the measuring tube b, or vice versa.-The cubic capacity of
the tube d, must be inconsiderable as compared with that of the bulb a, and
measuring tube b.
Fourthly The jacket space e, and casing f, enclosing the same and surrounding
the measuring tube b, and through which casing f, steam of practically constant
pressure and temperature is passed, or in which any other suitable medium is
contained or passed thus forming a jacket thereof so that the measuring tube b, and
its contained air or gas are maintained at a constant known temperature.
.
Fifthly. An automatic pressure regulator in which the free end of the measuring
tube b, is connected by means of the tube g, of small bore and of convenient length,
with the tube h, (which is hereinafter called the "barometer tube") placed
perpendicularly and closed hermetically at its upper end. In this barometer
tube h, the column i, of mercury is provided of sufficient height to give the desired
pressure on the gas contained in the measuring tube b.-The barometer tube h, is
much longer than the column i, of mercury contained therein, so that the changes
of volume occurring within the apparatus, cause the column i, to move up or down
in the tube h, without alteration of its length and consequently without alteration
of pressure, there being a vacuum above the mercury in the tube h.
In place of regulating the pressure of gas contained in the measuring tube b, by
connecting the upper part of that tube, that is to say, the part above the mercury
piston c, through the pipe g, with the barometer tube h, as shewn at Figure 2, the
pipe g, may be dispensed with, in which case the barometer tube is placed
immediately above, or forms a continuation of, the measuring tube b, and in such
case the two mercury pistons c, and i, shewn in Figure 2, are merged into one
piston or column j, of mercury as shewn at Figure 3.

page_text: The action of the construction of apparatus hereinbefore described and shewn at
Figures 1, and 2, is as follows:-
When the bulb or expanding vessel a, is beated, the expansion of the contained
gas causes a part of the said gas to be expelled through the connecting tube d, into
the measuring tube b-The piston c, of mercury is driven forwards or upwards in
the said tube b, and by suitable graduation the volume of the expelled gas is
measured by the position of the said piston c,.-The cubic capacity of the con-
necting tube d, being comparatively small the variations of the volume of the gas
contained in it as influenced by changes of temparature may be neglected without
seriously affecting the accuracy of the observations.
The temperature and pressure of the gas in the measuring tube b, are known and
constant, the expansion of the material of the bulb a, itself can be calculated, it is
therefore possible to measure, with any required accuracy, the expansion of the
original gas in the bulb a, under the influence of any unknown temperature, by
measuring the volume of the gas in the measuring tube b.
In the Instrument herein before described with reference to Figures 1, and 2, of
the annexed drawings, the volume of the gas or air within the said Instrument is
indicated by the position of the column i, of mercury in the tube h.-By the
instrument represented at Figure 3, the volume of the gas or air within the
instrument is directly regulated by the piston j, of mercury which, in this con-
struction of Instrument, performs the functions of the two mercurial pistons c,
and, represented at Figure 2, the position of this piston j, indicating the
temperature required to be ascertained.
The use of an automatic pressure regulator such as I have hereinbefore
described (of various forms,) obviates the necessity for barometric observation
such as would be needed if the free end of the measuring tube b, were open to
the atmosphere.
When however a pressure regulator is not used, it is advisable to have the scale
of the thermometer moveable, so that its zero point may be adjusted for the pressure
of the atmosphere at the time of observation.
The action of the improved apparatus herein before described depends on the
comparatively uniform expansion, by heat, of perfect gases under uniform pressure.
Hitherto no thermometer has come into ordinary use by which temperatures
above the boiling point of mercury, could be accurately indicated and observed by
mere inspection of a moveable indicator, but with the improved thermometers con-
stituting this Invention temperatures up to, and beyond, the softening point of
glass can be observed as easily as lower temperatures can now be with a mercury
thermometer.
Thermometers constructed according to this Invention may be graduated by
measuring the capacities of the bulbs a, and of the measuring tubes b, respectively,
thereafter marking off on the latter the volume of expelled gas corresponding
with ench temperature, using in these calculations the co-efficient for the expansion
of the gas at constant pressure.
The expansion of the gas in the bulb a, with increasing temperatures, causes a
decreasing amount to be expelled per degree, therefore the degrees as marked on
the measuring tube b, diminish in length towards the higher end of the scale, this
will be readily understood with reference to the diagram, Figure 6, hereinafter
described.
Certain fixed points of the scale may be determined by experiment as in the
graduation of mercurial thermometers, the graduation being completed by inter
and extra-polation.
To facilitate the graduation of thermometers, scales or diagrams, such as is
shewn at Figure 6, shewing the ratios of the various parts of the scale, are
prepared by a well known ge metric method to which a thermometer of any
length of measuring tube can be readily referred and from which it can be
graduated.

page_text: This diagram is or may be prepared from the markings or graduations of two
thermometers of varying sizes.-Figures 4, and 5, (Sheet 2.) show such markings or
graduation of two thermometers of varying sizes in which the measuring tubes
are maintained at 100° Centigrade.
Figure 6, is a diagram constructed from these two scales.-This diagram is
available for the ready graduation of thermometers whose ranges fall anywhere
between these scales. It is evident that by choosing two scales sufficiently
removed from each other in range, that is to say, whose sizes vary sufficiently, the
diagram may be adapted to include any intermediate scale.
The two scales, Figures 4, and 5, are simply laid parallel to each other at a
sufficient distance apart, and the corresponding graduation marks are joined by the
lines k.
To graduate a thermometer by the use of a diagram such as is shewn at Figure 6,
it is necessary to determine two fixed points in its range-preferably the freezing
and boiling points of water.-After marking these points on the thermometer, it
is applied to the diagram so that it is parallel with the two scales Figures 4, and 5,
and so that the freezing and boiling points fall on the intersecting lines k, of
0° and 100°--The other intersecting lines k, will indicate their corresponding
temperatures on the tube.
It is evident that the apparatus and system hereinbefore described, can be applied
for the determination of low, as well as of high, temperatures, and the said apparatus
may be constructed in various outward forms or shapes without departing from the
essential features of the Invention.
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
First. The improved system of thermometry under which, temperatures and
changes to temperature, are indicated by the measurement, at practically constant
temperature and pressure, of the volume of gas expelled from a vessel of given
capacity under the influence of the temperature which is to be measured all
substantially as berein before described.
Second. The apparatus consisting of expanding vessel, connecting tube, and
measuring tube, as combined for carrying out the system of temperature measure-
ment as herein before described with reference to the several Figures of the annexed
drawings.
Third. The jacket of steam or other temperature regulating medium at constant
temperature, for maintaining a constant temperature in the measuring tube of such
thermometers.
Fourth. The automatic pressure regulator as described with reference to
Figures 2, and 3, of the annexed drawings and as used in the system of
thermometry herein before set forth.
Dated this Nineteenth day of November 1884.
J. H. JOHNSON, DAY & JOHNSON,
Applicant's Agents.