Improved Long-range Barometer.
Year: 1891

page_text: Date of Application, 7th Dec., 1891
Complete Specification Left, 7th Sept., 1892-Accepted, 3rd Dec., 1892
PROVISIONAL SPECIFICATION.
Improved Long-range Barometer.
I JOHN JOLY Civil Engineer of 39 Waterloo Road Dublin do hereby declare-
the nature of this invention to be as follows: :-
In this barometer a column of mercury of about 26 inches in length is suspended
in a glass tube. Below it in the tube is glycerine or other suitable liquid of lesser
specific gravity.
This liquid communicates with the bath. The pressure of the atmosphere is
balanced by the column of mercury and the column of lighter liquid below the
mercury. The column of lighter liquid alone changes in length with change of
pressure, and the mercury moves up and down through a distance- depending upon
the specific gravity of the lighter liquid.
To sustain the mercury columu in a wide tube without friction a cylindrical.
piston fitting the tube freely with flat upper surface floats in the lighter liquid;
or it may have a projecting float on its upper surface which entering the base
of the mercury column, by its levity in the mercury, pulls the flat piston against
the base of the mercury column, and thereby keeps it from breaking.
Dated this 4th day of December 1891.
JOHN JOLY:
COMPLETE SPECIFICATION.
Improved Long-range Barometer.
I JOHN JOLY Civil Engineer of 39 Waterloo Road, Dublin 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 :-
In this barometer a column of mercury of a certain length is suspended in n.
straight, vertical glass tube closed at the upper end. Another liquid of lower
specific gravity, such as glycerine, creosote etc. occupies the tube below the mercury
as well as a bath below open to the atmosphere, into which the vertical tube dips.
The upper end of the tube is vacuous or contains only the vapours of the
liquids. The pressure of the atmosphere at the base of the tube is at any moment
balanced by the combined downward pressures of the column of mercury and of
the column of lighter liquid. The length of the latter column alone changes with
change of atmospheric pressure the liquid being drawn in from the bath or given
out to it; while the column of mercury exerting a pressure of constant intensity
moves up or down in the tube. By thus loading the lighter liquid by a column of
mercury the barometer is reduced to a convenient length while retaining the full
sensitiveness of a barometer entirely composed of the lighter liquid.
To sustain the column of mercury in the tube and yet leave it free to move up
and down without friction I use a disk d loosely fitting the tube and maintained
pressed against the base of the column of mercury m by the pull of a float f
which projects centrally from its upper surface and enters the base of the column of
mercury. The levity of the float in the mercury pulls the disk against the base
of the mercury column and so keeps the lower surface of the mercury from
breaking. The float and disk may be of any suitable material which does not
become acted upon by the mercury or by the lighter liquid b. The float may be
of any shape as spherical, ellipsoidal, etc. so long as it offers the suitable displace--
ment. It is preferably carried at the end of an iron pin p some two or three

page_text: inches in length projecting centrally and perpendicularly from the upper surface of
the disc and may be provided with three or more projecting points 8, 8, which loosely
fit the tube and so guard against the float pulling unequally upon the disk which
would turn the disk crooked in the tube.
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
A barometer composed of a liquid of low specific gravity loaded with a column
of mercury in the manner described so that the variations of atmospheric pressure
are entirely met by variations in the length of the column of lighter liquid; the
instrument thus preserving convenient dimensions while retaining the sensitiveness
of a barometer composed of the lighter liquid alone.
Dated this Sixth day of September 1892.
JOHN JOLY.