IMPROVEMENTS IN BAROMETERS
Year: 1861

page_text: LETTERS PATENT to Richard Howson, of Middlesbro'-on-Tees, in the
County of York, Engineer, for the Invention of "IMPROVEMENTS IN
BAROMETERS."
Sealed the 20th December 1861, and dated the 24th June 1861.
PROVISIONAL SPECIFICATION left by the said Richard Howson at the
Office of the Commissioners of Patents, with his Petition, on the 24th
June 1861.
I, RICHARD Howson, of Middlesbro'-on-Tees, in the County of York,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN BAROMETERS," to be as follows:-
My Invention consists in employing a tube similar to the common straight
barometer, except that in place of the entire bore of the tube being filled with
mercury or other fluid, the central part of it is occupied by a light stalk or
closed tube, leaving only a comparatively small concentric space for the
mercury or other fluid; and instead of making the cistern for the surplus
mercury or other fluid.fixed as in the ordinary barometer, it is attached to the
said stalk or closed tube, so that the stalk, cistern, and fluid are held in
suspension by the pressure of the atmosphere, and rendered free to rise or fall
by every increase or decrease of pressure. By this barometer the pressure of
the atmosphere can be ascertained either by the difference in the level between
the top of the mercury in the cistern and the top of the column in the tube,

page_text: by the position of the stalk and cistern, by the position of the top of the column
of mercury in the tube, or, lastly, by means of a dial and pointer, the motion
of which is derived from the motion of the cistern and stalk through the
intervention of suitable mechanism. The vertical movement of the stalk and
cistern, and the top of the column of mercury in the tube, can be made of any
required range of scale corresponding to any given increase or decrease of
pressure by adjusting the relative proportions of the barometer.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Richard Howson in the Great Seal Patent Office on the
24th December 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
Howson, of Middlesbro'-on-Tees, in the County of York, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fourth day of June, 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 said Richard Howson, Her special license that I, the said Richard
Howson, my executors, administrators, and assigns, or such others as I,
the said Richard Howson, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and at all times.
thereafter during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
MENTS IN BAROMETERS," upon the condition (amongst others) that I, the said
Richard Howson, by an instrument in writing under my hand and seal, 'should
particularly describe and ascertain the nature of the said Invention, and in
what manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Richard Howson, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the follow
ing statement thereof, and the accompanying Drawing, that is to say:-
My Invention consists in employing a tube similar to that of the common
straight barometer, except that in the place of the entire bore of the tube

page_text: being filled with mercury or other fluid, the central part of it is occupied by
a light stalk or closed tube, leaving only a comparatively small concentric
space for the mercury or other fluid; and instead of making the cistern for
the surplus mercury or other fluid fixed as in the ordinary barometer, it is
attached to the said stalk or closed tube, so that the stalk, cistern, and fluid
are held in suspension, and rendered free to rise or fall by every increase or
decrease of pressure.
The object of the Invention is to add to the sensitiveness of the well known
Torricellian column by giving it a comparatively increased range, or greater
extent of rise and fall; also to obtain barometric readings on an extended
scale otherwise than from the top of the column, if desired, and the mode in
which it is to be practically carried into effect in accordance with the above
description will be understood on reference to the Drawing hereto annexed.
The Drawing represents sections of the working parts of the instrument
when divested of its case and all those arrangements which are necessary to
render it complete, but are not required to illustrate the Invention.
A is the barometer tube; B, the cistern, and C, the stalk; these different
parts A, B, and C, being shewn in the position which they occupy relatively
to one another, and to the mercury with which the instrument is filled. The
tube A is freely suspended, and its lower end dips to a greater or less depth
into mercury contained in the cistern. The stalk C (which is supposed hero
to be of glass tube sealed at both ends) is attached to the bottom of the
cistern B concentrically therewith, and it passes axially up the tube A, termi-
nating a little below the top of the column a. The immediate consequence of
this arrangement is that the top of the stalk comes into a region of the
barometric column where the downward pressure upon it is necessarily very
small, so that there is an excess of upward pressure exerted by the atmosphere
outside, which tends to push the cistern upwards, and actually does so unless
the weight of the cistern with its contained mercury up to the level 6 (and
stalk included) is at least equal to such excess. So long as these opposing
forces are in equilibrio the cistern remains stationary, but if the cistern should
get lighter from any cause it will ascend, if it should get heavier it will
descend. This is precisely the action which takes place under the influence
of the fluctuations of atmospheric pressure. As soon as a barometric rise
occurs a portion of mercury leaves the cistern, passes into the tube, and
accumulates above the top of the stalk. The cistern simultaneously ascends
through the influence of the same force, and only comes to rest at a higher
level, when the increased displacement caused by the immersion of the tube A
in the mercury of the cistern exactly balances what has gone out of it; the

page_text: converse action of course holds good when a fall occurs in the pressure of the
atmosphere.. Thus it is that when the column moves, the cistern also moves
simultaneously, dragging the column with it, to a new, position, and the range
is enlarged over and above the ordinary barometric range by an amount which
is determined by the ratio which the internal area of the tube A bears to the
area of glass which bounds it.
The action of the instrument may also be regarded as that of a long piston
or plunger working in a cylinder, with a vacuum above it and a self-graduating
weight below. The stalk may be considered as the body of the piston, and
the mercury as a mobile packing. The piston moves in obedience to atmos-
pheric fluctuations, and the packing does so as well, the entire range of the
top of the column being compounded of the two motions, as before explained.
It will be inferred from the foregoing description that the most convenient
mode of taking observations with this construction of instrument will be to
read off the indications afforded by means of a scale applied to the top of the
column. This however is not the only way in which observations may be
taken. The scale for instance may be applied to the cistern, either vertically
to measure its motion direct, or circularly, that is to say, as a dial and pointer
(like that of the well known wheel barometer), the pointer being worked by
the motion of the cistern through the intervention of a rack and pinion, or
other suitable mechanism. Readings may also be taken by a system of
measuring the difference of level between the top of the column a and the
surface of mercury b in the cistern. All measurements taken in this manner
will clearly correspond to similar measurements taken from the common
standard barometer for the time being, any given oscillation will shew of the
same length in both instruments. The indications taken from either the top
of the column-or the cistern are not confined to any particular limit of range
on the contrary it is possible to obtain a great variety of ranges. For instance.
if the interior area of the tube A be made equal to the area of the material
of which it is composed, it is not difficult to see that the range of the cisterr
will be equal to the barometric range, and that of the top of the column wil
be double the barometric range. If a more extended range is required in any
proportion it is only necessary to make the internal area of A correspondingly
in excess of that of the annulus which bounds it, or, in other words, of the
displacing element. Reference has been made so far to a system of observation
which only enables us to know the state of the barometer during the time o
inspection, but it will be clear to all persons conversant with the subject that the
cistern affords special facilities for permanently recording its own movements, by
the adaptation to it of registering clockwork, such as is at present in use for

page_text: purposes of a similar character. The recording line may be traced on paper,
either continuously or dotted, by means of a pencil or other tracer, or by a
series of perforations, or photographically, all these systems being sufficiently
well understood, the last being also applicable to register the oscillations of the
top of the column as well as those of the cistern.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I would have it understood that, first, I do not
confine myself to any particular form of instrument, or details of external
construction not affecting the main features of the Invention. Second, neither
do I confine myself to the precise form and arrangement shewn in the Draw-
ing of those parts which do contain the essential features of the Invention,
these features in reality may be preserved consistently with various modifi-
cations. The stalk, for instance, is shewn as terminating underneath the top
of the column, but it might be preferred in some cases to make it pass com-
pletely into the vacuous space above it. Instead also of the tube A being of
uniform bore it might be made either larger or smaller at any part thereof. The
same remarks will also apply to the stalk in reference to its external shape.
Third, I do not claim as being new and of my Invention all the particulars
which have been described in the foregoing Specification; but what I do claim
is as follows-I claim the mode of supporting the cistern in free and sensitive
suspension by attaching a rigid stalk to the bottom of the said cistern, and
passing it up the axis of the Torricellian column, as herein-before described.
In witness whereof, I, the said Richard Howson, have hereunto set my
hand and seal, this Twentieth day of December, in the year of our
Lord One thousand eight hundred and sixty-one.
RICHARD HOWSON. (L.S.)