IMPROVEMENTS IN THE CONSTRUCTION OF BAROMETERS, AND IN APPARATUS FOR REGISTERING THE INDICATIONS OF THE SAME
Year: 1861

page_text: LETTERS PATENT to Thomas Telford Macneill, of 23, Cockspur Street,
in the County of Middlesex, for the Invention of "IMPROVEMENTS IN THE
CONSTRUCTION OF BAROMETERS, AND IN APPARATUS FOR REGISTERING THE
INDICATIONS OF THE SAME."
Sealed the 7th January 1862, and dated the 9th July 1861.
PROVISIONAL SPECIFICATION left by the said Thomas Telford Macneill
at the Office of the Commissioners of Patents, with his Petition, on the
9th July 1861.
I, THOMAS TELFORD MACNEILL, of 23, Cockspur Street, in the County of
Middlesex, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE CONSTRUCTION OF BAROMETERS, AND IN APPARATUS FOR REGISTERING
THE INDICATIONS OF THE SAME," to be as follows:--
The object of one part of this Invention is to multiply or increase the
indications of the variable heights of the column of mercury in barometers to
such an extent that the small variations in height which are scarcely appreciable
in barometers of ordinary construction may be read off with the greatest
facility. To effect this I construct a tube either wholly or partially of glass,
and more or less of a greater length than the tubes of ordinary barometers.
The top part of this tube is enlarged to a certain extent, and is closed whilst

page_text: the bottom portion is open, and is surrounded with either a closed casing of
glass or any other suitable material, or with a solid mass of wood, cork, or
any other suitable light substance serving as a float. This tube is filled with
mercury and inverted in a vessel containing mercury in the ordinary manner
in which barometers are prepared, so that a vacuum exists in a considerable
portion of the upper enlarged part of the same.
The tube will then sink
into the mercury contained in the vessel until the buoyancy of the immersed
part at the bottom of the tube causes the same to float. The tube is main-
tained in its upright position by fixed rings through which it passes, which
rings have pointed set screws guiding the tube during its vertical motion so
as to diminish friction, or the tube may be held in any other suitable manner.
By this arrangement, according as the pressure of the atmosphere increases
or diminishes, not only does the mercury rise or fall in the tube to the usual
extent, but the tube itself sinks or rises to an extent varying with the proportion
between the inside area of the enlarged portion of the tube and the sectional
area of the float which is immersed in the mercury. Thus, by fixing a vertical
scale upon the upper enlarged portion of the tube the increase of height of
the column of mercury, plus the extent of downward motion of the tube
itself, will be read off for an increase of pressure in the atmosphere, and vice
wersa for a decrease of the same, thus increasing the apparent rise and fall
of the mercury in the tube to any desired extent. Another scale may also
be fixed by the side of the tube, upon which may be
rise and fall of the same, independently of the rise and fall of the mercury.
This amount of rise and fall of the tube, owing to a decrease or increase in
the pressure of the atmosphere, may be made to be greater or less than or
equal to the rise and fall of the column of mercury in the same according
as the area of the interior of the upper enlarged part of the tube and that of
the immersed float are proportioned? Upon the before-mentioned second
fixed scale, or upon a third fixed scale, may also be read off the amount of
rise and fall of the column of mercury independent of that of the tube. A
valuable feature in this barometer is, that it is 'self-adjusting, that is to say,
no matter what is the rise or fall of the column of mercury in the tube, the
level of the mercury in the fixed vessel will always remain the same, inasmuch
as for an increase in the pressure of the atmosphere, the amount of mercury
displaced by the sinking of the tube- is precisely, the same as that which
passes up into the enlarged part of the tube-owing, to, the rising of the column
of mercury, and it is evident that the reverse will take place for a decrease in
the pressure of the atmosphere...
read off the amount of

page_text: The object of another part of this Invention is to ascertain the pressure of
the atmosphere expressed by weight. For this purpose I attach to the upper
end of the before-described tube one end of a fixed lever balance, the other
end of which has a receptacle for weights. According as the tube has a
tendency to rise or fall with a decrease or increase in the pressure of the
atmosphere, it will require more or less weight in the scale to maintain the
balance in equilibrio, which increase or decrease of the weights placed on the
scale will indicate the fluctuation in the pressure of the atmosphere. Or I
attach the upper end of the before-mentioned tube to a fixed spring balance,
which, as the tube rises or falls, will indicate the decrease or increase in the
pressure of the atmosphere. Or in place of the before-described tube I
construct a tube of equal internal diameter throughout, and either wholly of
glass, or the lower part may be of metal, of equal or nearly equal specific
gravity with mercury. The upper closed end of this tube, in which there is
as usual a vacuum, I attach 'to a fixed spring balance, whilst the open lower
end is immersed in the mercury in the fixed vessel. It will be evident that
if the spring balance is so constructed that when carrying the empty tubė
the index of the same stands at zero, then when a vacuum is formed in the
tube in the ordinary manner the balance will exactly indicate the pressure of
the atmosphere upon an area equal to that of the interior of the tube, which
will consequently rise or fall until held in equilibrio by the tension on the
spring of the balance, or the minimum pressure of the atmosphere may be
balanced by weights attached to a lever balance or over a pulley, and the
fluctuations in the pressure only may be sustained by the spring balance.
The object of another part of my Invention is to cause such before-described
barometers to be self-registering. For this purpose I attach to the tube
which rises and falls a pencil or a pointed rod projecting out horizontally.
Behind this tube, and nearly touching the point of the pencil or rod, I place a
sheet of paper of a width proportionate to the rise and fall of the tube, and
each end of which paper is attached to a vertical roller fixed one on each
side of the tube, a considerable portion of the paper is wound round one of
the rollers, and these are caused to revolve by clockwork in such a manner
that the paper is gradually unwound from one roller and wound up on the
other, being thus made to pass slowly in a horizontal direction behind the
barometer tube. Behind this paper is placed a vertical prism having any
desirable number of flat sides, upon each of which may be fixed a piece of
different coloured transfer paper, the length of which corresponds with the
width of the paper on the rollers. This prism is so arranged by clockwork

page_text: in any convenient manner as to be pressed forward at certain intervals, and
thus bring the before-mentioned paper against the point of the pencil or rod
attached to the barometer tube, which by aid of the transfer paper will make
an impression on the recording paper. By this arrangement a diagram
representing the various fluctuations in the height of the barometer tube
during a given time may be obtained. When, after a certain lapse of time,
the paper has been all unwound from one of the before-mentioned rollers and
wound up on the other, the before-described prism is turned so as to bring a
different coloured transfer paper against the recording paper, and this latter is
unwound from the rollers and wound up again upon them in the original
position, so that a fresh diagram of a different colour may be taken on the
same paper, and this is repeated as often as there are different coloured papers
on the prism. Or in place of the before-mentioned prism, a simple flat object
may be employed, having transfer paper upon it, and actuated in the before-
described manner, and a fresh recording paper may be employed for every
diagram. To steady the barometer tube a finger may be made to press
against the same at the point where the pencil is fixed, in the reverse direction
to the pressure of the paper against the pencil every time that such an
impression takes place. Instead of having a separate mechanism to impart
motion to the before-described registering apparatus, the same may receive its
motion from a cluck.attached to the barometer.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Telford Macneill in the Great Seal Patent Office
on the 9th January 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
TELFORD MACNEILL, of 23, Cockspur Street, in the County of Middlesex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of July, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
suid Thomas Telford Macneill, Her special licence that I, the said Thomas.
Telford Macneill, my executors, administrators, and assigns, or such others
as I, the said Thomas Telford Macneill, my executors, administrators, and
assigns, should at any time agree with, and no others, from time to time and

page_text: 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, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN THE CONSTRUCTION OF BAROMETERS, AND IN APPARATUS FOR
REGISTERING THE INDICATIONS OF THE SAME," upon the condition (amongst others)
that I, the said Thomas Telford Macneill, my executors or administrators, by
an instrument in writing under my, or their, or one of their hands and seals,
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 Thomas Telford Macneill, 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, reference being had to the accompanying Drawing,
and to the letters and figures marked thereon (that is to say):-
The object of one part of this Invention is to multiply or increase the indi-
dications of the variable heights of the column of mercury in barometers to
such an extent that the small variations in height which are searcely appreci
able in barometers of ordinary construction may be read off with the greatest
facility. To effect this I construct a tube either wholly or partially of glass,..
and more or less of a greater length than the tubes of ordinary barometers...
The top part of this tube is enlarged to a certain extent, and is closed, whilst
the bottom portion is open, and is surrounded with either a closed casing of:
glass or any other suitable material, or with a solid mass of wood, cork; or any
other suitable light substance serving as a float. This tube is filled with
mercury, and then inverted in a vessel containing mercury, in the ordinary:
manner in which barometers are prepared, so that a vacuum will thus be:
formed in a considerable portion of the upper enlarged part of the tube. 1
the tube is then left to itself it will sink into the mercury contained in the
cistern, until the buoyancy of the immersed part of the float at the bottom of
the tube balances the pressure of the atmosphere on the top of the tube, plus.
the weight of the tube itself, when the tube will float or be suspended in the
mercury contained in the cistern. The tube is maintained in its upright:
position by fixed rings through which it passes, which rings have pointed set
screws, guiding the tube during its vertical motion, so as to diminish friction
or the tube may be held in any other suitable manner.
By the above-described arrangement, according as the pressure of the atnio

page_text: sphere increases or diminishes,, not only does the mercury rise or fall in the
tube to the usual extent, but the tube itself,sinks or rises to an extent varying
with the proportion between the inside sectional area of the upper enlarged
portion of the tube and the sectional area of the float which is immersed in the
mercury.
Figures 1 and 2 on the accompanying Drawing shew the construction of
my improved barometer. Figure 1 shews an elevation, and Figure 2 shews a
longitudinal section of the same. .
A is the barometer tube, of which the upper part B is enlarged; C is the
float, consisting of a glass tube which surrounds the tube A, forming an
annular space between the two, which space is closed at the bottom, and thus,
when immersed in the mercury contained in the cistern D, displaces the same,
and by its buoyancy sustains the pressure of the atmosphere upon the top of
the part B of the tube, the-weight of a certain portion of the mercury in the
part B, as also the weight of that part of the tube itself which is out of the
mercury in the cistern. The tube is maintained in its upright position by a
fixed ring E through which it passes, in which ring are pointed set screws e, e,
guiding the tube in its motion without any appreciable friction. It will be
readily understood that if, at a certain pressure of the atmosphere, the column
of mercury, stands at a height equal to 1, indicated in Figure 1, and the tube
is maintained by the float C at a height equal to h+h', above the level of the
mercury in the cistern, then if the pressure of the atmosphere diminishes to
a considerable extent, not only will the column of mercury in the tube fall to
the level, as shewn in Figure 2, but at the same time the buoyancy of
the float C will, on account of the diminished pressure of the atmosphere on the
top of the tube, and also from the less weight of mercury in the tube B, cause
the tube to rise up out of the cistern until it again becomes stationary at a
height equal to h²+h, thus making the amount of relative motion of the
mercury in the tube, or the apparent fall of the mercury equal to h-h
instead of h h2, which latter is the difference of level indicated by ordinary
barometers, that is to say, if a scale a be fixed upon the upper part B of the
tube, the relative motion of the level of the mercury along that scale will be
the distance to which the mercury will fall ordinarily, plus the height to which
the tube itself will rise, and vice versa, for an increase of pressure of the atmo
sphere. A second scale b, fixed independently of the barometer tube, will indi-
cate the ordinary, rise and fall of the column of mercury, whilst a third fixed
scale c will indicate the rise and fall of the tube itself, independently of that
of the mercury. This rise and fall of the tube can be made to be greater than

page_text: or equal to or less than the rise and fall of the mercury itself, according as the
annular sectional area of the float C is proportioned to the internal sectional
area of the part B of the tube. Thus, in Figure 3 is shewn an arrangement
in which the motion of the tube is considerably less than in the arrangement
of Figures 1 and 2, owing to the difference between the area of the float C
and that of the upper part of the tube B being greater in the former than in
the latter case. In all cases the sectional area of the float must be somewhat
in excess of that of the interior of the tube B.
A valuable feature in this improved barometer is, that the level of the
mercury in the reservoir D is always constant, no matter what the rise and fall
of the mercury in the tube may be, for it will be evident that by the sinking of
the tube just the same amount of mercury must be displaced, as is forced up
into the tube by the increased pressure of the atmosphere, and vice versa, for
a decrease of pressure.
In some cases I attach to the tube a small extra conical float F, as shewn in
Figure 3, the object of which is to compensate by its variable buoyancy for
the increase and decrease of weight of the tube to be sustained by the float C,
according as the tube is immersed to a lesser or greater extent in the mercury
of the cistern, or I sometimes make the float C itself conical to the required
extent.
I also sometimes make the sectional area of the float C exactly the same as
the internal area of the upper part B of the tube, and increase the sectional
area of the extra conical float to such an extent that it shall also contain the
excess of area over the internal area of the tube B,,which is necessary for
giving the requisite exaggerated motion to the tube.
Although I prefer to make the float C. of glass, as described, I sometimes
also make it of thin metal, or other substance that is not injuriously acted
upon by the mercury, or I make it solid, of wood, cork, or any other suitable
light substance. When it is only required to register the motion of the baro-
meter tube without any reference to the level of the mercury in the same, I
sometimes make the whole of the barometer tube A, upper chamber B,. and
floats C and F of metal or other suitable material that is not affected by the
mercury.
In some cases I make the barometer tube of the same internal diameter
throughout, and proportion the area of the float accordingly.
The object of another part of my Invention is to cause such before-described
barometer to be self-registering. Figure 4 on the accompanying Drawing
shews one arrangement I adopt for this purpose. To the fixed frame A is

page_text: attached the cistern B of the barometer, in which the tube C works up and
down in the manner before described. To the top of this tube is fixed a small
arm D, carrying either a pencil or pointed rod E. The upper part of the
frame A is made of a width corresponding with the amount of rise and fall of
the tube C, and between grooves a, a, formed on it a board F is caused to
slide immediately behind the barometer tube C, but at such a distance that the
pencil E does not quite touch it ordinarily. This board F has a rack G
attached to it, in which rack a pinion H, moved by the clock I, gears, so that
by the motion of the clock the board F is caused to travel very slowly in the
direction of the arrow, a small weight J being attached to it to facilitate its
motion. A second rack K is attached to the face of the board, in the teeth of
which a pawl L attached to the rod M works. The rod M is attached at top
and bottom to the frame A, so that it can turn on its axis, but is acted upon
by a small spring m in such a manner that it always presses the pawl Lagainst
the rack K. The rod M has further attached to it two arms N, N, carrying
a second rod O, situated immediately in front of the arm D of the barometer
tube.
By this arrangement it will be seen that as the board F travels along, the
short lever or pawl L will alternately be pushed outwards by the teeth of the
rack K, thus turning the rod M and bringing the rod O away from the arm D
of the tube, and will then be forced back into the next space between the teeth
of the rack by the spring m, by which the rod O will be caused to press the
pencil E against the board F, thus registering the height at which the tube C
stood at that moment, by means of a dot upon a sheet of paper fixed on the
board F, with a sheet of transfer paper behind it. Thus, at fixed intervals of
time, a series of dots at different levels corresponding with the height of the
barometer tube at the end of those intervals will be recorded on the paper,
forming a more or less exaggerated Diagram of the variations in the height of
the column of mercury in the barometer during a certain period of time. I
sometimes also provide the rod O at the bottom with a fixed pencil or pointed
rod, as shewn at Q, which would always mark a dot at a constant level at the
same time that the dots representing the heights of the barometer tube are
recorded, thus forming a datum line somewhat below the lowest level to which
the tube can sink, from which line the variations of height can readily be
measured. Or the pencil or pointer may be fixed to the frame A, and so
arranged as to draw a continuous datum line on the paper as the board F
moves along. When the board has moved to its extreme position after the
lapse of such a period, the paper is removed, and is replaced by a fresh sheet;

page_text: the pinion H is drawn out of gear with the rack G by a small lever P, and the
board F is pushed back into its other extreme position for commencing a fresh
diagram.
Another arrangement which I adopt is shewn in Figures 5 and 6 on the
accompanying Drawing. Figure 5 shews a part elevation, and Figure 6 shews
a sectional plan of the arrangement. Behind the top of the barometer tube C,
which is furnished with a pencil or pointed rod E, is placed a sheet of paper A
of a width corresponding with the motion of the barometer tube, and each end
of which is wound round each of the cylinders or rollers B, B', attached to the
frame F. One of these rollers B has a spiral spring G attached to it, by which
it is caused to pull the paper in the direction of the arrow, and unwind it off
the roller B'; this roller is connected by gearing 6 to the clock H in such a
manner that it is only allowed to deliver the paper A according to the motion
of the clock. Immediately behind the paper A and barometer tube C is fixed
a prism I of any required number of sides. Upon each side of this prism is
attached a piece of different colored transfer paper, and a different side of the
prism is turned to the front every time the paper is rewound upon the
cylinder B. This prism is connected by levers J, J, to the spindle K, which
is caused by the clockwork to turn at certain intervals slightly on its axis, and
by this means to bring the prism, and with it the paper, against the point of
the pencil E, thus causing a dot to be made upon the paper of the particular
color of the transfer paper then in front. By this means a series of different
colored Diagrams of the fluctuations of the barometer during different periods
of time may be made upon one piece of paper. Instead of moving the prism
against the pencil, as described, the pencil may be pressed against the prism in
a manner similar to that indicated in Figure 4, and instead of connecting the
escapement of the roller B to the clock, it may have a separate escapement.
Another arrangement which I adopt is shewn in Figures 7 and 8. Figure 7
shews a part elevation, and Figure 8 shews a plan of cylinder & tube.
Here the paper upon which the Diagram is traced is fixed round á cylinder A,
which is caused to revolve by the gearing a connecting it with the clock B.
The arm D with the pencil E attached to the barometer tube C is at stated
intervals pressed against the paper on the cylinder A by means of the rod F,
and levers G, G, attached to the spindle H, which receives a slight motion
round its axis by means of gearing in connection with the clock B.
Another arrangement for registering the accumulated rise of the tube
of my improved barometer during a given time, combined with an
arrangement for registering the maximum and minimum indications of the

page_text: tube is shewn in Figures 9, 10, and 11 on the accompanying Drawing ;
Figure 9 shews a front view of the accumulator; Figure 10 shews a side
view of the apparatus; and Figure 11 shews a front view of the maximum
and minimum apparatus. A is the top part of the moveable tube of my
improved barometer, as before described; to this is attached, by means of
a slight cord a passing over the wheel C, a very small weight B. The wheel C
runs very loosely on the spindle D fixed to the frame X by means of brackets
Z, Z', and is caused by means of the cord a to revolve when the tube A rises
or falls; this wheel C is connected to the dial E, which also runs loose on the
spindle D by means of a slight spring c attached to the wheel, which catches in
the small serrations formed round the circumference of the back face of the
dial E. This dial is also provided with serrations or teeth upon its edge, in
which a pawl F catches, and which are so formed that the pawl will allow the
dial to revolve in the direction of the arrow, but not in the reverse direction.
By this arrangement, when the tube A rises, it causes the wheel C, and with
it the dial E to revolve, but when the tube sinks, as the dial cannot move in
the reverse direction, the slight spring c will be made to loose its hold in the
serrations by the pull on the wheel C, which will revolve as the barometer
tube sinks. Thus, a hand or pointer K being placed on the fixed spindle D,
the portion of a revolution of the dial past this pointer during a certain interval
of time will indicate the accumulated rise of the barometer tube during that
time. The pointer K can be moved round on the spindle D to any required
position, according to where the zero point of the dial E is situated at the
commencement of the observations.
In the arrangement for registering maximum and minimum indications
shewn in Figure 11, J is a fixed annular dial graduated on its circumference,
and held by the bracket Z' of the framing. On the fixed spindle D are placed
two hands H and I, which are actuated by the projecting pin G fixed on the
face of the revolving wheel C, so that when this wheel revolves in one direction
in consequence of the tube A descending, the pin G will come against the hand
I, or maximum indicator; and as this moves with a very slight friction on the
spindle D, it will follow the motion of the pin G until the wheel C begins' to
revolve in the reverse direction, in consequence of the tube A rising, when, the
hand I remaining stationary, will register the maximum indication of the
barometer tube. In the same manner the pin G will move the hand H in the
reverse direction, and cause it to register the minimum indications of the baro-
meter tube. In order that the hands H and I may be brought to the same point
at the commencement, of the observation, they are bent out, as shewn, where

page_text: the pin G comes against them. It is obvious that the various moving parts of
this apparatus must be made very light, and must move as free as possible.
Having now described the nature of my Invention, and in what manner
the same is to be performed, what I claim under the before in part recited
Letters Patent is,―
Firstly, the construction of barometers, in which the tube is freely sus-
pended in the mercury contained in a fixed cistern by means of one or more
floats attached to it, and which tube rises and falls vertically, or nearly so, by
the action of this float, according to the lesser or greater pressure of the
atmosphere, substantially as herein-before described.
Secondly, registering the rise and fall of the tubes of such before-described
barometers, according to the variations in the pressure of the atmosphere by
means of apparatus, substantially as herein-before described.
In witness whereof, I, the said Thomas Telford Macneill, have here-
unto set my hand and seal, this Fourth day of January, in the year
of our Lord One thousand eight hundred and sixty-two.
TELFORD MACNEILL. (L.8.