IMPROVEMENTS IN THERMOMETERS
Year: 1885

page_text: I ANDREW HADDOW of 1 Keith Place, Easter Road, Edinburgh (Engineer) in
the county of Edinburgh do hereby declare the nature of my invention for
IMPROVEMENTS IN THERMOMETERS to be as follows:-
Thermometers as hitherto made are liable to shew errors in course of time due to
the contraction of the bulb causing the mercury in the stem to indicate a higher
temperature than it should; also, the mercurial column is often difficult to read
owing to it's extreme fineness and the object of the present invention is to provide
an easy means of correcting thermometers, so that for a given temperature they can
be made quite accurate, and also to render the mercurial column more easily seen,
These objects are effected by attaching the end of the thermometer tube furthest
away from the bulb to a sliding piece which can be moved longitudinally in the
scale for a short distance, equal to five degrees or less of the thermometer scale.
The sliding piece and attached tube can be moved into the correct position and
fixed there by tightening a screw.
The mercurial column is made more easily read by making the thermometer tube
with the inner portion of the tube of glass having a greater index of refraction
than the outer portion of the tube. The mercurial column is thus magnified more
than it would be by using only one kind of glass and so there is less chance of
misreading The thermometer tube is attached to the sliding piece beforementioned
by one or more turns of a wire instead of fixing the tubo to the scale by clamps
and screws as is now customary,

page_text: I ANDREW HADDOW of 1 Keith Place, Easter Road, Edinburgh, in the county of
Edinburgh Engineer do hereby declare the nature of my invention for IMPROVE-
MENTS IN THERMOMETERS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
Thermometers as hitherto made are liable to shew errors due to contraction or
dilation of the bulb causing the mercury, alcohol or other liquid in the stem or tube
to indicate a higher or lower temperature than it should. A permanent error due
to contraction of the bulb begins to take place as soon as the thermometer tube is
finished or made and the error continues to increase for ten months or more.
Temporary errors are caused by the thermometer being exposed to very sudden,
great changes in temperature which produce a temporary contraction or dilation of
the bulb, and the object of the present invention is to provide a means of quickly
and easily correcting these permanent and temporary errors without the assistance
of anyone accustomed to repairing thermometers..
This object is effected by providing an easy means of quickly shifting the
thermometer tube along the scale until the correct position is attained, when the
thermometer tube is again fixed to the scale in the position to which it has been
brought.
Various arrangements of mechanism are suitable for rendering the thermometer
tube adjustable with relation to the scale but I find the apparatus hereinafter
described with reference to the accompanying drawing specially suited for
correcting the errors due to the contraction or dilation of the bulb.
This invention is applicable only to thermometers in which the scale is separate
from the thermometer tubo although it may be in contact with the thermometer
tube.
Fig. 1 represents a thermometer constructed or arranged according to my
invention for the correction of errors due to, or caused by the contraction or
dilation of the bulb.
Fig. 2 is a longitudinal section and Fig. 3 is a transverse section shewing the
sliding piece hereinafter described, with the manner of attaching the thermometer
tube to the sliding piece and of attaching the sliding piece to the scale.
An opening "O" is made in the thermometer scale B into which is passed the
sliding piece A A, with its attached screw S.
A piece of rubber or other clastic material is laid on the sliding piece at C, the
thermometer tube is laid on the rubber or other clastic material and is fastened to
the sliding piece A A, by winding a wire or string of metal or other material round
the tube and sliding piece as shewn at D.
The ends of the wire or string are twisted or tied behind the scale or are soldered
together to prevent unwinding.
The sliding piece A. A, has two lugs as shewn at L. The sliding piece has a
hole in it at E into which a part of the thermometer tube is fitted. The scale B is
cut away at G to allow the bulb room to move longitudinally.

page_text: Although I have described a sliding piece with only one screw in it, there may
be two or more screws for fixing it to the scale and although my drawing shews
part of the sliding piece on the back of the scale it may be all on the face of the
scale and with the screw or screws inserted from the back of the scale instead of
from the front as shewn on drawing.
The method of correcting or adjusting a thermometer constructed according to
my invention is as follows. The screw S is slackened. The thermometer is placed
in water kept steadily at the desired temperature for a sufficient interval of time
along with another thermometer which is known to be correct or with which the
thermometer to be adjusted is desired to agree at the given temperature. When
the mercury, or other liquid is steady in the thermometer tubes the sliding
piece A A, with it's attached screw S and with the attached thermometer tube
to be adjusted are shifted into the desired position so that both thermometers
indicate the same temperature. The sliding piece with it's attached thermometer
tube is then fixed in this position by tightening the screw S. A mark can be
made on the scale with the point of a needle or penknife which will indicate the
position to which the sliding piece was brought when the thermometer was
corrected or adjusted.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
(1.) The sliding piece, essentially as and for the purpose herein before described.
(2.) The construction of thermometers having a sliding piece, essentially as and
for the purpose herein before described.
(3.) The manner or method of attaching the thermometer tube to the sliding
picce essentially as herein before described.