IMPROVEMENTS IN APPARATUS FOR BAROMETRICAL AND THERMOMETRICAL PURPOSES
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Leonhard Wollheim at the
Office of the Commissioners of Patents, with his Petition, on the
18th February 1868.
I, LEONHARD WOLLHEIM, of Triest, in the Empire of Austria, but
at present of Gloucester Gardens, Hyde Park, in the County of
Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN APPARATUS FOR BAROMETRICAL AND THERMOMETRICAL
PURPOSES," to be as follows:-
I construct an apparatus for barometrical and thermometrical purposes
consisting mainly of two hollow vessels communicating with each other
by means of a tube, of which the one vessel is closed while the other
is open at top. These vessels are filled with a fluid, by preference
mercury, in such a manner that the fluid encloses a certain quantity
of air or other suitable gas in the closed vessel, while in the other
vessel it is in contact with the atmosphere. These combined vessels
are so connected to the beam of a balance that any passage of mercury
from the one vessel into the other owing to a change in the atmospheric
pressure will disturb the equilibrium of the balance by producing a
preponderance on the one side thereof and thus cause it to alter its

page_text: position. As from the construction of the vessels it is evident that,
irrespective of any change of atmospheric pressure, a change of tem-
perature will also affect the equilibrium of the balance, I counteract or
neutralize such latter effect upon the equilibrium of the balance by
adding to the apparatus a contrivance so arranged that a change of
temperature shall affect it in such a manner as to produce a pre-
ponderance on the other side of the balance beam equal to the pre-
ponderance produced by the same change of temperature in the
combined vessels, whereby it will be evident that any alteration in the
position of the balance beam will indicate only a change of atmospheric
pressure. The aforesaid contrivance may consist either of another
closed vessel nearly filled with mercury, the expansion or contraction of
which by variations of temperature will produce the desired prepon-
derance;. or it may consist of an arrangement of bars or rods formed of
two different metals that expand unequally under the action of heat
and which consequently alter their relative positions under a change
of temperature, and thus also produce the desired preponderance.
..
The apparatus is furthermore provided with a scale and a pointer, by
means of which the angles of deviation of the balance beam are made
to indicate the variations of atmospheric pressure which produce such
deviations. If it be desired to adapt the apparatus for indicating
variations of atmospheric pressure beyond the range of those which it
is ordinarily intended to indicate this may be effected by adding to
the one side of the balance beam a corresponding weight. For
measuring altitudes the graduated marks on the scale of deviation of
the apparatus may have numbers indicating either the differences of
pressure of the atmosphere or the corresponding different altitudes
instead of the different pressures of the atmosphere or the corresponding
height of the column of mercury. In order to determine the divisions
of the scale of deviation it is only necessary to determine two points
of the same by empirical means, after which all the others may bo
obtained by construction.
If the two modifications of the apparatus before mentioned are so
arranged that at times the two combined vessels first described may
be entirely removed or turned in a horizontal direction to an angle of a
90° degrees with the longitudinal axis of the apparatus this can be
converted into an oscillating thermometer. The communication between
the two combined vessels may also be intercepted by means of a cock

page_text: placed in the connecting tube. By means--of a contrivance the entire
balance beam may be raised off its bearings, securely fixed, and at the
same time the before-mentioned open vessel closed by means of an
elastic cover. The horizontal adjustment of the apparatus is effected
by means of a spirit level attached thereto. The case serving for the
transport of the apparatus is so arranged that it serves as a protection
at the points of observation against the detrimental action of the wind.