Year: 1888

page_text: I, JOHAN GUSTAF WIBORGH, of Stockholm, in the Kingdom of Sweden, Professor
of the School of Mines, do hereby declare the nature of this invention, to be as
follows:-
This invention has reference to a method of determining temperatures by means of
which it will be possible to measure temperatures of various degrees with equal
precision, and this in so simple a manner that most persons can make accurate
observations.
As the apparatus or instrument employed for carrying out this invention in conse-
quence of its construction depends on the height of the barometer when the
observation is made, such apparatus can also be used to determine the atmospheric
pressure with perfect certainty and great ease.
According to this invention the determinations are arrived at with an instrument
consisting of two hollow bulbs or chambers which communicate with each other and
with the outer air or atmosphere as also with a manometer. When making an
observation after having cut off the communication with the atmosphere, the air in
these bulbs or chambers is compressed and the air of the one bulb driven into the air
of the other which latter bulb afterwards contains the two volumes of air. The power
necessary for this is measured by the manometer. If the question be to determine
temperature, that bulb in which the two air volumes are compressed-the thermometer
bulb-must before the observation is made and before the communication with the
outer air is cut off, be at that degree of heat which is to be determined while the other
bulb remains at the temperature of the surrounding air. If on the other band the
height of the barometer is to be determined, both the bulbs must be of the same
temperature at the time of observation. In the former case the height of the mano-
meter gives the temperature, in the latter the barometric pressure.
If V be the volume of air at To contained in the thermometer bulb, V¹ the volume
of air at to which is forced in, the pressure above and beyond the barometric
pressure H necessary for the compression, and a the co-efficient of dilatation of
the air, it follows that after the outer air has been cut off and the volume VI of air
pressed into the volume V has arrived at the temperature To.

page_text: In this equation the expansion of the thermometer bulb has not been taken into
account since in most cases the influence thereof is of no consequence. The above
equations prove:
Firstly, that an instrument constructed according to this invention gives the
difference between the temperature of the thermometer-bulb and the original
temperature of the air impressed therein.
Secondly, that when the difference of temperature is zero, the instrument has a
point of zero. to which corresponds a manometer pressure
.
Thirdly, that the increase of the manometer pressure is always proportional to the
difference of temperature i.e. that the length of a degree of temperature on the scale
is just as great whether. the temperature be high-or low.
Fourthly, that the instrument can be simply graduated by calculation for if h be
measured when the difference of temperature be zero and the barometric pressure be
known, then the for the instrument in question is also known and by inserting
V¹
V
a difference of temperature of e.g. 100 degrees in the formula the size of the parts of
the scale may be directly obtained and the scale be drawn.
Fifthly, by adapting the size of the thermometer-bulb and the volume of the air
which is pressed in, a greater or smaller length of the parts of the scale for different
instruments can be obtained just as in the mercury thermometers where the same result
is arrived at by using various proportions between the volume of the bulb of the
thermometer and the diameter of the tube of the thermometer.
If, in the above equation T°= t° or if the two bulbs are of the same temperature the
equation is reduced to h
V¹
=
H.or H. =
=
V
V
Vi
V
=
h whence since
VI
is constant for
every instrument, H.-h times this constant. By a suitable construction of the
instrument and by the use of a scale drawn up according to the proportions between
the bulbs used, a barometer is obtained, which contains no vacuum.
In the accompanying drawings Fig. 1 represents in front view an air-pyrometer
according to this invention. Fig. 2 is a side view thereof, partly in section. Fig. 3
represents a modification of a part thereof. Fig. 4 represents a manometer scale for
different barometric pressures. Fig. 5 is a front view of a modified form of pyrometer,
with three bulbs. Fig. 6 represents in front view another modification of the
pyrometer and Fig. 7 is a similar view with a thermometer placed in the bulb V¹,
a barometer.
Fig. 8 shows an apparatus according to this invention adapted as
Figs. 9, 10 and 11 represent a combination of the pyrometer with the barometer,
Fig. 9 being a front elevation and Figs. 10 and 11 sections on the lines 10-10 and
11-11 in Fig. 9.
In all these figures the same letters signify the same or corresponding parts.
In Figs. 1 and 2 which represent a pyrometer, V denotes the bulb into which the
air is pressed or the thermometer-bulb. It can be of arbitrary form, and be made of
metal, china, or other suitable substance.
This bulb is connected by a capillary tube B with a manometer which near to the
capillary tube is provided with an extension or bulb, denoted as V1 for determining
the volume of air which is to be pressed into the thermometer-bulb. This volume V of
air is decided by two lines or marks m and n situate above and below the bulb. M is
a channel, by which the air in V. and V₁ may communicate with the outer air. A is

page_text: a covering plate fixed on an elastic arm which by the screw E can be pressed against
the outer end of the channel M. and close it. The closing of this channel may also
be accomplished in any other suitable manner; for instance the screw E may itself be
screwed towards and shut the channel M as represented in Fig. 3.
To determine the power necessary for the pressure mentioned above, it is convenient
to use mercury in the manometer, although other fluids may also be used. K is a
ball or bag of suitable material such as gutta percha to contain the mercury. By
pressing this ball or bag the necessary quantity of mercury may be pressed into the
manometer, so as to cause the pressure of the air in the bulbs necessary for the
observation. In the instrument shown the ball or bag K is shut in by a bent portion
of the plate O to which the instrument is fixed. By a screw E¹ a bow Q that passes
through the plate may be moved together with a plate N connected with its legs,
thus causing the necessary pressure, which, however, may be obtained in many other
ways. G is a pinching device, with which the ball, on moving the instrument, may
be entirely shut off from the manometer, after having introduced all the mercury
into the former. C is the thermometer-scale, which is made movable in a vertical
direction, so that the zero point may be adjusted according to different barometric
pressures.
The thermometer bulb and a more or less lengthy portion of the capillary tube can
advantageously be made separate and be joined to the manometer in any suitable
manner. Figs. 2 and 3 show two ways. In the former the end of the capillary tube
of the manometer is placed in a cavity in the end of the capillary tube B of the
thermometer; in the latter both the end of the capillary tube B and the end of the
manometer are placed in a connecting piece or socket L.
To enable a new thermometer bulb to be easily put in position if it should become
necessary, instead of fixing the capillary tube B in the socket L, it may be cemented
into a separate socket, which can be screwed on to the socket L; this arrangement
is not shown in the drawings.
If temperature is to be determined with this instrument the bulb of the thermometer
is placed in that space where the degree of heat is to be ascertained (as in an oven, gas
pipe, etc.) and allowed to remain there until the bulb is of the same temperature as
this space. During this time the screw E is so arranged that the air in the bulbs V
and V communicates with the outer air or atmosphere.
Afterwards, having brought the mercury of the manometer to the level of the
mark n, the communication with the outer air is shut off by the screw E and the
mercury raised in the manometer to the mark m, by which means the fixed volume
of air V is driven into the bulb of the thermometer. The mercury has then risen
still higher in the other tube or leg of the manometer, and by its height directly
shews on the scale C the difference of temperature existing between that of the
bulb of the thermometer and that of the air before being pressed into the thermo-
meter bulb. The temperature sought is thus obtained by adding the degree observed
on the scale C to the degree of heat of the air pressed in, which is usually like
that of the surrounding air, but can otherwise be ascertained by a thermometer
placed in the bulb V', as shown in Fig. 7.
After the observation is made the mercury in the manometer is first lowered to, the
mark.n or thereabouts, after which the channel M is opened. The instrument is then
again ready for use for a new determination of temperature.
As it is of importance that the mercury in the manometer be lowered to the mark n
or thereabouts before the channel M is opened, it is of advantage if the instrument
be provided with some arrangement which compels an observer not used to the
instrument, to lower the mercury by means of the screw E¹, before the channel is
opened by the screw E. This may be done in various ways. One method is shown
in Fig. 2, where one of the legs of the bow Q is connected with the one end P
of a two armed lever, the other. end H of which supports a plate, which is moved
below the screw E, when the ball K is squeezed. Thus the screw E is not accessible
until, by means of the screw E', the mercury has been lowered in the manometer.
Before making an observation of the temperature, the position of the zero of the

page_text: scale c must be decided according to prevailing barometric pressure. As shown by
the formula for the point of zero, this is done in complete agreement with the
observations of temperature just described, except that since T must be equal to t, the
bulbs V and V¹ must be of the same temperature for this determination. The scale c
is thereupon moved until its point of zero coincides with the top of the column of
mercury.
The shifting of the scale of the above mentioned instrument is in a vertical direction
by means of the screw F. It must, however, be remembered that as different
barometric pressures require somewhat different lengths of the parts of the scale, when
the temperature is to be ascertained with great nicety, a correction becomes necessary
when the barometric pressure is different from that for which the scale has been con-
structed. In order to avoid this, a scale such as shown in Fig. 4 may be used which
can be employed for all the ordinary barometric pressures. This scale is fixed
between guides in such a manner that it can be moved in a horizontal direction behind
the manometer tube, until its line of zero coincides with the point of zero of the
instrument which depends on the prevailing barometric pressure and is decided in the
manner just described. Instead of deciding the point of zero in this manner it is also
possible when the barometric pressure is known from a common barometer or
otherwise, to move the scale in such a manner that the vertical line drawn, or
imagined to be drawn, on the scale (see Fig. 4) which answers to a given barometric
pressure, falls just behind the tube of the manometer.
A third way of arranging the scale is that of placing several scales or one like that
shown in Fig. 4 and mounting it on a movable cyclinder close to the manometer tube,
as shown in Figs. 9 to 11. When a degree of temperature is to be determined this
cylinder is turned so that the readings of the temperature can be taken from the scale
answering to the barometric pressure.
V1
Fig. 5 represents an instrument which is arranged for different degrees of sensibility.
As the size of the parts or the length of the degrees of the scale is proportional
to v
different degrees of sensibility can be obtained with the same instrument by
providing the manometer with two (or more) bulbs (V₁ V".....) and three (or more)
marks (m n n¹......) instead of one bulb (V) and two marks (m n). When using
this instrument for high temperatures, only the air volume V¹ between the two upper
marks n and m is to be pressed in. If, on the contrary, the instrument is to be used
for relatively low and extremely nice determinations of temperature, the whole of the
air volume V + V", which is between the marks m and n¹ is to be compressed into
the thermometer bulb. Two different scales c are requisite for this instrument.
Instead of the air volumes V and V₁ being in communication with the outer air by a
special channel M, the instrument may be so arranged that this communication exists
through the tube of the manometer D (see Fig. 6). With this arrangement before
the observation is made the mercury must be kept below the line n, so that the air in
the bulb of the thermometer can freely communicate with the outer air. When an
observation is to be made, and the mercury for this purpose is forced up to the
mark m, the mercury itself, as a matter of course, shuts off all communication of the
thermometer bulb with the outer air, as soon as it has reached to the height of n, and
a certain given volume V' is always compressed into the bulb of the thermometer.
By this arrangement the instrument is simplified and rendered easier of manage-
ment, as for every determination of temperature it is only necessary to adjust the
surface of the mercury once with nicety, viz. at the mark m.
For the purpose of graduating the instrument, when the pressure is to be
measured while V and V¹ are of the same temperature, a special channel M is
nevertheless requisite in order that the level of the surface of the mercury may be
read in the manometer, when the mercury is raised to the mark m and stands in both
tubes under atmospheric pressure.. As shown in Figs. 9 and 10, the instrument may
be provided with such a channel, although it need not be used for observations of
temperature in general. Fig. 6 shows, although only as an example, an air
thermometer without a separate channel M and with the bulb of the thermometer, the

page_text: capillary tube and manometer made of glass and in one piece. Such an instrument
can, as a matter of course, only be used for comparatively low temperatures.
An instrument according to this invention can as hereinbefore mentioned be used
for making barometrical observations. Fig. 8 represents such a barometer in
elevation, where the bulbs V and V₁ communicate with the outer air through the
manometer -D. If it be desired to make the instrument short that part of the
manometer tube D, from which the readings are taken, can be made sloping as shown
by Fig. 8 so as to obtain better and plainer results. For the sake of symmetry and
in order that the instrument may be easily made perpendicular, on which the accuracy
of the result depends, the manometer tube can be bifurcated above, in which case
however, it must always be remembered that when making an observation the
instrument should be in such a position that the same result is obtained on both the
scales. S (Fig. 8) denotes a movable pointer. The observations are made in
the before mentioned manner. Before the observation is made the mercury must be
adjusted so low that V and V¹ communicate with the outer air, but on making the
observation, the mercury is driven upwards by the screw E¹ or in some other suitable
manner to the mark m, after which the barometric pressure is read on the scale.
This barometer can be made of any height, has no vacuum, is easy of removal and
transportation and if kept exactly vertical gives absolutely reliable readings.
In order that, even when the bulbs V and V' are at a different temperature, the
proper position of the point of zero, or what is the same thing, the barometric
pressure prevailing, may at any time be determined, the previously mentioned
barometer can be combined with the air thermometer. Figs. 9 and 10 show such an
arrangement. The manometer at a point somewhat below the tube D is provided with
an additional manometer tube, which ends in the bulb V. When the point of zero
is ascertained that is to say when V and VI are at the same temperature and the
mercury is raised to the mark m, the mercury rises in the additional manometer tube
to a certain height, where another mark m² is set. When this instrument is used, and
the bulb V is introduced into an oven or gas pipe or other place the temperature of
which is to be ascertained, the mercury in the manometer should be kept so low, that
all three bulbs V,, V₁ and V communicate with the outer air by the manometer
tube D. When the determination of the temperature takes place, the mercury is
raised until it reaches the mark m and at the same time reaches a height in the
manometer tube D, which corresponds to the point of zero of the instrument at
the prevailing barometric pressure, according to which point of zero the scale of the
thermometer is now adjusted. The mercury is afterwards forced on to the mark m',
when its height in the manometer tube D, without any further correction for
barometric pressure, always shows the correct temperature on the scale.
In order to conveniently adjust a scale corresponding to the point of zero of the
instrument, found in the manner just mentioned, scales can be drawn for different
barometric pressures, and be fastened on a cylinder R (Figs. 9-11) which can be
revolved by a knob T until the scale with the proper point of zero reaches the
manometer tube D. This tube as well as the scale cylinder is partly protected by a
surrounding plate J.
If the bulb of the thermometer V and the capillary tube B be made of china, glass
or such like material they may in order to protect them, be surrounded by a casing of
metal which may be so arranged as not to unnecessarily conduct heat to the other
parts of the instrument; for this latter purpose when fixing the casing, it can be
isolated by a packing of asbestos or other suitable material (not shown in the
drawings).
1
คา
1
1000

page_text: COMPLETE SPECIFICATION.
0
Improvements in and Apparatus for Determining Temperatures and
Barometric Pressures.
I, JOHAN GUSTAF WIBORGH, of Stockholm, in the Kingdom of Sweden,
Professor of the School of Mines, 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:-
This invention has reference to a method of determining temperatures by means
of which it will be possible to measure temperatures of various degrees with equal
precision, and this in so simple a manner that most persons can make accurate
observations. As the apparatus or instrument employed for carrying out this
invention in consequence of its construction depends on the height of the barometer
when the observation is made, such apparatus can also be used to determine the
atmospheric pressure with perfect certainty and great ease. According to this
invention the determinations are arrived at with an instrument consisting of two
hollow bulbs or chambers which communicate with each other and with the outer
air or atmosphere as also with a manometer. When making an observation after
having cut off the communication with the atmosphere, the air in these bulbs or
chambers is compressed and the air of the one bulb driven into the air of the other
which latter bulb afterwards contains the two volumes of air. The power necessary
for this is measured by the manometer. If the question be to determine temperature,
that bulb in which the two air volumes are compressed-the thermometer bulb-must
before the observation is made and before the communication with the outer air
is cut off be at that degree of heat which is to be determined while the other bulb
remains at the temperature of the surrounding air. If on the other hand the height
of the barometer is to be determined both the bulbs must be of the same temperature
at the time of observation. In the former case the height of the manometer gives
the temperature, in the latter the barometric pressure. If V be the volume of air
at To contained in the thermometer bulb, V' the volume of air at to which is forced
in, h the pressure above and beyond the barometric pressure H necessary for the
compression, and a the co-efficient of dilatation of the air, it follows that after the
outer air has been cut off and the volume V¹ of air pressed into the volume V has
arrived at the temperature To.

page_text: The above equations prove
Firstly, that an instrument constructed according to this invention gives the
difference between the temperature of the thermometer bulb and the original
temperature of the air impressed therein.
Secondly, that when the difference of temperature is zero, the instrument has a
point of zero, to which corresponds a manometer pressure
Thirdly, that the increase of the manometer pressure is always proportional to the
difference of temperature i.e. that the length of a degree of temperature on the
scale is just as great whether the temperature be high or low.
Fourthly, that the instrument can be simply graduated by calculation for if h be
measured when the difference of temperature be zero and the barometric pressure be
known, then the for the instrument in question is also known and by inserting a
V¹
V
difference of temperature of e.g. 100 degrees in the formula the size of the parts of
the scale may be directly obtained and the scale be drawn.
Fifthly, by adapting the size of the thermometer-bulb and the volume of the air
which is pressed in, a greater or smaller length of the parts of the scale for different
instruments can be obtained just as in the mercury thermometers where the same
result is arrived at by using various proportions between the volume of the bulb of
the thermometer and the diameter of the tube of the thermometer.
=
If, in the above equation T to or if the two bulbs are of the same temperature
the equation is reduced to h H or H
every instrument, H
=
V¹
V
V
=
V
Vi
h, whence since
VT is constant for
h times this constant. By a suitable construction of the
instrument and by the use of a scale drawn up according to the proportions between
the bulbs used, a barometer is obtained which contains no vacuum.
In the drawings filed with my provisional specification.
Fig. 1 represents in front view an air-pyrometer according to this invention.
Fig. 2 is a side view thereof partly in section.
Fig. 3 represents a modification of a part thereof.
Fig. 4 represents a manometer scale for different barometric pressures.
Fig. 5 is a front view of a modified form of pyrometer, with three bulbs.
Fig. 6 represents in front view another modification of the pyrometer and
Fig. 7 is a similar view with a thermometer placed in the bulb V¹.
Fig. 8 shews an apparatus according to this invention adapted as a barometer.
Figs. 9, 10 and 11 represent a combination of the pyrometer with the barometer,
Fig. 9 being a front elevation and Figs. 10 and 11 sections on the lines 10-10
and 11-11 in Fig. 9. In all these figures the same letters signify the same or
corresponding parts.
In Figs 1 and 2 which represent a pyrometer, V 'denotes the bulb into which the
air is pressed or the theremometer bulb. It can be of arbitrary form, and be made
of metal, china or other suitable substance. This bulb is connected by a capillary
tube B with a manometer which near to the capillary tube is provided with an
extension or bulb, denoted as V₁ for determining the volume of air which is to be
pressed into the thermometer bulb. This volume V' of air is decided by two lines or
inarks m and n situate above and below the bulb. M is a channel, by which the
air in V and V1 may communicate with the outer air. A is a covering plate fixed on
an elastic arm which by the screw E can be pressed against the outer end of the
channel M and close it. The closing of this channel may also be accomplished in any
other suitable manner; for instance the screw E may itself be screwed towards and
shut the channel M as represented in Fig. 3. To determine the power necessary for
the pressure mentioned above, it is convenient to use mercury in the manometer,

page_text: although other fluids may also be used. K iş a ball or bag of suitable material such
as gutta percha to contain the mercury.
By pressing this ball or bag the necessary quantity of mercury may be pressed into
the manometer, so as to cause the pressure of the air in the bulbs necessary for the
observation.
G is
In the instrument shewn the ball or bag K is shut in by a bent portion of the
plate O to which the instrument is fixed. By a screw E¹ a bow Q that passes through
the plate may be moved together with a plate N connected with its legs, thus causing
the necessary pressure; which however, may be obtained in many other ways.
a pinching device with which the ball, on moving the instrument, may be entirely
shut off from the manometer after having introduced all the mercury into the former.
is the thermometer scale which is made movable in a vertical direction, so that the
zero point may be adjusted according to different barometric pressures.
The thermometer bulb and a more or less lengthy portion of the capillary tube can
advantageously be made separate and be joined to the manometer in any suitable
manner.
Figs. 2 and 3 shew two ways. In the former the end of the capillary tube of the
manometer is placed in a cavity in the end of the capillary tube B of the thermometer,
in the latter both the end of the capillary tube B and the end of the manometer are
placed in a connecting piece or socket L. To enable a new thermometer bulb to
be easily put in position if it should become necessary, instead of fixing the capillary
tube B in the socket L, it may be cemented into a separate socket, which can be
screwed on to the socket L; this arrangement is not shewn in the drawings. If tem-
perature is to be determined with this instrument the bulb of the thermometer is
placed in that space where the degree of heat is to be ascertained (as in an oven, gas
pipe, etc.) and allowed to remain there until the bulb is of the same temperature as
this space.
During this time the screw Ę is so arranged that the air in the bulbs V and V₁
communicates with the outer air or atmosphere. Afterwards, having brought the
mercury of the manometer to the level of the mark n the communication with the
outer air is shut off by the screw E and the mercury raised in the manometer to
the mark m by which means the fixed volume of air V₁ is driven into the bulb
of the thermometer. The mercury has then risen still higher in the other tube or
leg of the manometer, and by its height directly shews -on the scale C the difference
of temperature existing between that of the bulb of the thermometer and that of the
air before being pressed into the thermometer bulb. The temperature sought is thus
obtained by adding the degree observed on the scale C to the degree of heat of the
air pressed in, which is usually like that of the surrounding air, but can otherwise
be ascertained by a thermometer placed in the bulb V¹, as shewn in Fig. 7.
After the observation is made the mercury in the manometer is first lowered to the
mark n or thereabouts, after which the channel M opened.
The instrument is then again ready for use for a new determination of temperature.
As it is of importance that the mercury in the manometer be lowered to the mark n or
therabouts before the channel M is opened, it is of advantage if the instrument be
provided with some arrangement which compels an observer not used to the instrument,
to lower the mercury by means of the screw E', before the channel is opened by the
screw E.
This may be done in various ways.
One method is shewn in Fig. 2, where one of the legs of the bow Q is connected
with the one end P of a two armed lever, the other end H of which supports a
plate, which is moved below the screw E, when the ball K is squeezed.
Thus the screw E is not accessible until, by means of the screw E, the mercury
has been lowered in the manometer. Before making an observation of the temperature
the position of the zero of the scale c must be decided according to prevailing
barometric pressure.
As shown by the formula for the point of zero, this is
done in complete agreement with the observations of temperature just described

page_text: except that since T must be equal to t, the bulbs V and V₁ must be of
the same temperature for this determination. The scale c is thereupon moved until
its point of zero coincides with the top of the volume of mercury. The shifting of
the scale of the above mentioned instrument is in a vertical direction by means of the
screw F. It must, however, be remembered that as different barometric pressures
require somewhat different lengths of the parts of the scale, when the temperature is
to be ascertained with great nicety, a correction becomes necessary when the
barometric pressure is different from that for which the scale has been constructed.
In order to avoid this, a scale such as shewn in Fig. 4 may be used which can be
employed for all the ordinary barometric pressures.
This scale is fixed between guides in such a manner that it can be moved in a
horizontal direction between the manometer tube, until its line of zero coincides with
the point of zero of the instrument which depends on the prevailing barometric
pressure and is decided in the manner just described. Instead of deciding the point
of zero in this manner it is also possible when the barometric pressure is known from
a common barometer or otherwise to move the scale in such a manner that the vertical
line drawn, or imagined to be drawn, on the scale (see fig. 4) which answers to a
given barometric pressure falls just behind the tube of the manometer. A third way
of arranging the scale is that of placing several scales or one like that shewn in
fig. 4 and mounting it on a movable cylinder close to the manometer tube, as shewn
in figs. 9 to 11. When a degree of temperature is to be determined this cylinder is
turned so that the readings of the temperature can be taken from the scale answering
to the barometric pressure. Fig. 5 represents an instrument which is arranged for
different degrees of sensibility. As the size of the parts or the length of the degrees
of the scale is proportional to different degrees of sensibility can be obtained
V¹
V
with the same instrument by providing the manometer with two (or more)
bulbs (V V...) and three (or more) marks (m n n'
.) instead of one bulb (V¹)
and two marks (m n).
When using this instrument for high temperatures, only the air volume V₁
between the two upper marks n and m is to be pressed in. If, on the contrary, the
instrument is to be used for relatively low and extremely nice determinations of
temperature, the whole of the air volume V + V" which is between the marks in
and n¹ is to be compressed into the thermometer bulb. Two different scales c are
requisite for this instrument.
Instead of the air volumes V and V² being in communication with the outer air
by a special channel M, the instrument may be so arranged that this communication
exists through the tube of the manometer D (see fig. 6). With this arrangement
before the observation is made the mercury must be kept below the line n so that the
air in the bulb of the thermometer can freely communicate with the outer air.
When an observation is to be made, and the mercury for this purpose is forced up
to the mark m the mercury itself, as a matter of course, shuts off all communication
of the thermometer bulb with the outer air as soon as it has reached to the height
of n and a certain given volume V₁ is always compressed into the bulk of the
thermometer. By this arrangement the instrument is simplified and rendered easier
of managment as for every determination of temperature it is only necessary to
adjust the surface of the mercury once with nicety viz. at the mark m. For the
purpose of graduating the instrument when the pressure is to be measured while V
and V³ are of the same temperature, a special channel M is nevertheless requisite, in
order that when the mercury is raised to the mark m it may stand in both tubes
under atmospheric pressure and its height in the manometer tube be correctly read
off. As shewn in Figs. 9 and 10, the instrument may be provided with such a
channel, although it need not be used for observations of temperature in general.
Fig. 6 shews, although only as an example, an air thermometer without a separate
channel M and with the bulb of the thermometer, the capillary tube and manometer
made of glass and in one piece. Such an instrument can, as a matter of course, only
be used for comparatively low temperatures.

page_text: An instrument according to this invention can as hereinbefore mentioned be used
for making barometrical observations. Fig. 8 represents such a barometer iu
elevation, where the bulbs V and V₁ communicate with the outer air through the
manometer D. If it be desired to make the instrument short that part of the
manometer tube D, from which the readings are taken, can be made sloping as shewn
by Fig. 8 so as to obtain better and plainer results. For the sake of symmetry and
in order that the instrument may be easily made perpendicular, on which the accuracy
of the result depends, the manometer tubo can be bifurcated above, in which case
however, it must always be remembered that when making an observation the
instrument should be in such a position that the same result is obtained on both the
scales. S (fig. 8) denotes a movable pointer.
Before the observation
The observations are made in the before mentioned manner.
is made the mercury must be adjusted so low that V and V₁ communicate with the
outer air, but on making the observation, the mercury is driven upwards by the
screw E¹ or in some other suitable manner to the mark m, after which the barometric
pressure is read on the scale. This barometer can be made of any height, has no
vacuum, is easy of removal and transportation and if kept exactly vertical gives
absolutely reliable readings. In order that, even when the bulbs V and V₁ are at a
different temperature, the proper position of the point of zero, or what is the same
thing, the barometric pressure prevailing, may at any time be determined, the
previovsly mentioned barometer can be combined with the air thermometer.
Figs. 9 and 10 shew such an arrangement. The manometer at a point somewhat
below the tube D is provided with an additional manometer tube, which ends in
the bulb Vin
When the point of zero is ascertained that is to say, when V and V₁ are at the
same temperature and the mercury is raised to the mark m, the mercury rises in the
additional manometer tube to a certain height, where another mark m' is set. When
this instrument is used, and the bulb V is introduced into an oven or gas pipe or other
place the temperature of which is to be ascertained, the mercury in the manometer
should be kept so low, that all three bulbs V, V₁ and V communicate with the outer
air by the nanometer tube D. When the determination of the temperature takes
place the mercury is raised until it reaches the mark m² and at the same time reaches
a height in the manometer tube D, which corresponds to the point of zero of the
instrument at the prevailing barometric pressure, according to which point of zero
the scale of the thermometer is now adjusted.
The mercury is afterwards forced on to the mark m, when its height in the
manometer tube D, without any further correction for barometric pressure, always
shews the correct temperature on the scale. In order to conveniently adjust a scale.
corresponding to the point of zero of the instrument, found in the manner just
mentioned, scales can be drawn for different barometric pressures, and be fastened on
a cylinder R (figs. 9-11) which can be revolved by a knob T until the scale with
the proper point of zero reaches the manometer tube D. This tube as well as the
scale cylinder is partly protected by a surrounding plate J. If the bulb of the
thermometer V and the capillary tube B be made of china, glass or such like material
they may in order to protect them, be surrounded by a casing of metal which may
be so arranged as not to unnecessarily conduct heat to the other parts of the
instrument; for this latter purpose when fixing the casing, it can be isolated by a
packing of asbestos or other suitable material (not shewn in the drawings).
Having now particularly described, and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what
I claim is
1. The method of ascertaining temperatures substantially as herein before described,
the said method consisting in forcing into a determinate volume of air which has
been brought under atmospheric pressure to the temperature which it is desired to
ascertain, another determinate volume of air which is, previous to the forcing
operation, at atmospheric pressure and of known temperature, the pressure required

page_text: to effect the operation being a measure of the difference of temperature of the two
volumes of air immediately before the observation.
2. The method of ascertaining barometric pressure substantially as hereinbefore
described, the said method consisting in forcing into a determinate volume of air
another known volume of air; both volumes being previous to the operation at
barometric pressure and at the same temperature, the pressure required to effect the
operation being a measure of the barometer pressure substantially as described.
3. An air thermometer constructed and arranged substantially as described with
reference to figs. 1 to 3 of the drawings.
4. An air thermometer constructed and arranged, substantially as described with
reference to fig. 5 of the drawings.
5. An air thermometer constructed and arranged substantially as described with
reference to fig. 6 of the drawings.
6. A barometer constructed and arranged substantially as described with reference
to fig. 8 of the drawings.
7. An air thermometer and barometer combined, constructed and arranged,
substantially as described with reference to figs. 9 to 11 of the drawings.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., -
Agent for the Applicant.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., -
Agent for the Applicant.