An Improvement in Barometers.
Year: 1892

page_text: Date of Application, 29th June, 1892
Complete Specification Left, 28th Mar, 1893--Accepted, 13th May, 1893
PROVISIONAL SPECIFICATION.
An Improvement in Barometers.
I, CLEMENT OSBORN BARTRUM, Bachelor of Science of the University of
London, of 19 Well Walk Hampstead N.W., Woollen Merchant do hereby declare
the nature of this invention. to be as follows:-
The object of my invention is to obtain a barometer, in which the variations in
inches of mercury of ordinary barometers are extended to variations on a more-open
scale; and which is not so cumbrous or expensive as such instruments as the glycerin
barometer, at the same time without being less accurate, and which may be
extremely sensitive to small and rapid changes of atmospheric pressure.
In carrying out my invention, I form the lower part of the instrument of a
column of mercury and a cistern, as in any ordinary barometer. The barometer
tube, in the neighbourhood of the upper termination of the mercury column, is
expanded to a larger calibre, and above the surface of the mercury is again
contracted. This narrow portion above is sufficiently long to allow of extreme
pressures being indicated, and is closed at the upper end, and may or may not
terminate with an enlargement. Upon the mercury rests a liquid of small specific
gravity compared with that of mercury, such as glycerin, aniline, methyl-salicylate
or some suitable substance, in sufficient quantity to fill the wide part of the tube
not occupied by mercury, and a part of the narrower portion above.
It follows from the above description, that, when the mercury column rises a
given distance, say one inch, in the wide portion, the other liquid will rise a greater
distance, viz. as many times one inch as the sectional area of the one portion is
greater than that of the other.
The increase of atmospheric pressure indicated by a given rise in the narrow
portion will correspond to the fall of mercury in the cistern, added to the rise of
mercury in the wide portion of the tube, added to the increase of length of the
column of the other liquid, the last reduced to its equivalent of mercury;
The rise of the liquid. in the upper portion corresponding to an increase of
pressure of one inch of mercury nay, according to the ratio of the diameters of the
wide and narrow portions, and to the specific gravity of the liquid employed, be as
much as 8, 10, 12 or more inches.
.
Any suitable method of construction may be employed. The method I adopt is
as follows. The tube having been put together of the requisite proportions and the
upper end left open, a short distance below this end the tube is drawn into a narrow
constriction. The open end is then connected with a Sprengel or other suitable
pump. A stopcock is placed in the connection with the pump for the admission of
the liquid. Mercury is then poured into the cistern and is pumped up the tube as
high as possible. The requisite amount of liquid is now admitted by the stopcock
and the latter carefully closed. The pumping is now continued until all traces of
air, or water vapour, or any gas or volatile substance dissolved by the liquid, has
been removed, this removal being facilitated by heating the liquid. The pumping
When
must be continued at intervals, for days if necessary, until this is the case.
a good permanent vacuum has been obtained, the tube is fused at the narrow
constriction and closed, and the pump removed. It onl, remains to measure the
lengths of the columns of the two liquids, and hence the pressure, corresponding to
a particular point on the tube. The pressure for other points can then be calculated
from the previously measured specific gravity of the upper liquid and the diameters
of the wide and narrow portions.
D30 1aw of Tune 1902

page_text: .1.
COMPLETE SPECIFICATION.
An Improvement in Barometers.
I, CLEMENT OSBORN BARTRUM Bachelor of Science of the University of
London, of 19, Well Walk, Hampstead, N.W., Woollen Merchant, 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, reference being had to the accompanying drawing and to the figures and
letters marked thereon:-
The object of my invention is to obtain a barometer in which the variations in
inches of mercury of ordinary barometers are extended to variations on a more open
scale and which is not so cumbrous or expensive as, such instruments as the
glycerine barometer, at the same time without being less accurate and which may
be extremely sensitive to small and rapid changes of atmospheric pressure.
In carrying my invention into effect I form the lower part of the instrument of a
column of mercury and a cistern as in any ordinary barometer..
In the accompanying drawing which represents a vertical section in two parts
of my improved barometer, the cistern a is of glass and is fused on to the laterally
bent lower end of the mercury tube b.
The barometer tube 6 in the neighbourhood of the upper termination of the
mercury column has a bulb or chamber c of larger calibre and above the same is a
smaller tube d which is preferably of like calibre to the mercury tube . This
tube d is sufficiently long to allow of extreme pressures being indicated and is
closed or sealed at the upper end.
Upon the top of the mercury in the chamber c rests a liquid of small specific
gravity compared with that of mercury, such for instance as glycerine aniline,
methyl salicylate or other suitable liquid in sufficient quantity to fill that part of
the chamber c not occupied by mercury and a part of the tube d above such
chamber c.
The increase of atmospheric pressure indicated by a given rise of the liquid in
the tube d, will correspond to the fall of mercury in the cistern a added to the rise
of mercury in the chamber c, added to the increase of length of the column of the
liquid in the tube d, the last reduced to its equivalent of mercury.
The rise of the liquid in the tube d corresponding to an increase of pressure of
one inch of mercury, may according to the ratio of the diameters of the chamber c
and the tube d and to the specific gravity of the liquid employed in the tube d be
.as' much as 8 or 10 inches.
Any suitable method of construction of the barometer may be employed. The
method have adopted and which I have found to answer is as follows. The various
parts of the tube having been put together of the requisite proportions and carefully
dried and the upper end of the tube d left open, a short distance below this end the
tube d is drawn into a narrow constriction. The open end is then connected with
a.Sprengel or other suitable pump. A stop cock is placed in the connection with
the pump for the admission of the liquid. Mercury is then poured into the cistern a
and is pumped up the tube as high as possible.
The requisite amount of liquid of light specific gravity is now admitted to the
tube by the stopcock and the latter carefully closed. The pumping is now
continued until all traces of air, or water vapour, or any gas or volatile substance
dissolved by the liquid has been removed, this removal being facilitated by heating
the liquid.
The pumping must be continued at intervals for days if necessary, until this is
When a good permanent vacuum has been obtained, the tube d is fused
at the narrow constriction and closed and the pump removed.
the case.
It only remains to measure the lengths of the columns of the two liquids and
hence the -pressure, corresponding to a particular point on the tube d.

page_text: The pressure for other points can then be calculated from the previously
measured specific gravity of the upper liquid and the diameters of the chamber c
and tube d.
The scale may however be pointed or laid off by comparison with a standard
barometer in the ordinary manner or other convenient means may be employed.
The drawing represents a constriction a between the upper and lower portions
of the cistern a, this constriction is adapted to receive a stopper of suitable
description when it is desired to render the barometer portable.
I would here remark that I do not confine myself to the method herein shown
and described of forming the cisterna and attaching it to the tube as such form
no part of my invention and can be arranged in any suitable manner and I would
further remark that I am aware of the long range or open scale barometer consisting
of a mercurial syphon tube to the short leg of which is attached a length of glass
tubing of much smaller bore than that of the mercury tube but which rises to about
the same height as the latter is open at its upper end and is supplied with a liquid
of much lighter specific gravity than mercury but in this class of barometer the
rise in pressure is indicated by a fall in the level of the light liquid in the narrow
bore tube thus reversing the ordinary reading in addition to which the said light
liquid is open to atmospheric influence.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The improved construction of barometer substantially as herein shown and
described and for the purpose stated.
2. In a barometer the combination with a lower tube connected with a mercury
cistern of a larger bored chamber or enlargement at the upper part of such tube,
a small bore tube above and in communication with such chamber or enlargement
exhausted and closed at its upper end, a column of mercury in the cistern and lower
tube and rising into the intermediate enlargement or chamber and a supply of
liquid of light specific gravity above the mercury and rising into the upper small
tube substantially as herein shown and described and for the purpose stated.
Dated this 28th day of March 1893
C. O. BARTRUM,
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.