IMPROVEMENTS IN THERMOMETERS.”
Year: 1874

page_text: LETTERS PATENT to Henry Negretti and Joseph Warren Zambra, both
of Holborn Viaduct, in the City of London, Meteorological Instrument
Makers, for the Invention of "IMPROVEMENTS IN THERMOMETERS.”
"
Sealed the 9th March 1875, and dated the 10th September 1874.
PROVISIONAL SPECIFICATION left by the said Henry Negretti and
Joseph Warren Zambra at the Office of the Commissioners of
Patents, with their Petition, on the 10th September 1874.
We, HENRY NEGRETTI and JOSEPH WARREN ZAMBRA, both of
Holborn Viaduct, in the City of London, Meteorological Instrument
Makers, do hereby declare the nature of the said Invention for "Im«
PROVEMENTS IN THERMOMETERS," to be as follows:—
Our Invention of improvements in thermometers relates, 1st, to that
class of instruments known as minimum thermometers; and, 2nd, to
what are usually termed "clinical" thermometers, or those used for
medical purposes.

page_text: In minimum thermometers there is usually attached to the graduated
tube a short supplementary tube and bulb, into which (after the mercury
in the graduated tube has sunk to the minimum point) any excess of
mercury will pass on an increase or rise in the temperature taking place.
Upon taking an observation, and resetting the instrument, the mercury
is to be run out of the supplementary bulb. It has been found in
practice that a portion of the mercury is liable to stick in this supple-
mentary bulb, and break off at the neck, so that a correct observation
cannot be taken.
The object of our first improvement is to remedy this defect, which is
done by dispensing with the small bulb, and substituting for it a chamber
terminating with a capillary tube, or elongating the small tube, and
drawing down the bore of this tube to a point.
When the supplementary tube is constructed in this manner the
mercury will have no tendency to stick to the end of the tube, as is now 1
the case.
This supplementary tube may either be attached to the bulb
behind, or it may be placed in front of the bulb, and between it and the
indicating part of the tube.
Our second improvement relates to clinical or medical thermometers
in which, in place of mercury, we employ alcohol for the indicating
column, as colored alcohol is more easily seen than the very fine column
of mercury which has heretofore been employed in thermometers of this
kind.
In constructing the tube we make it with a wide bore just above the
bulb, such wide bore being of sufficient length to take the column of
alcohol up to that point of temperature where it is required to take the
medical observation, say up to 90°. From this point the bore is
narrowed to a very fine onc, so that from 90° up to, say, 98° the thermo-
meter will be very sensitive. At some point between these two
degrees, say at 96°, we make a zero mark, which indicates the tempera-
ture of good health. The tube is then graduated above and below tho
zero point, and the alcohol, by rising above or falling below that point,
wiil Indicate ether a feverish or a low state of health.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Negretti and Joseph Warren Zambra in the
Great Seal Patent Office on the 10th March 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
NEGRETTI and JOSEPH WARREN ZAMBRA, both of Holborn Viaduct,
in the City of London, Meteorological Instrument Makers, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of September, in the year
of our Lord One thousand eight hundred and seventy-four, in the
thirty-eighth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto us, the said Henry Negretti and Joseph
Warren Zambra, Her special licence that we, the said Henry Negretti
and Joseph Warren Zambra, our executors, administrators, and assigns,
or such others as we, the said Henry Negretti and Joseph Warren
Zambra, our 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
"IMPROVEMENTS IN THERMOMETERS," upon the condition (amongst others)
that we, the said Henry Negretti and Joseph Warren Zambra, our
executors or administrators, by an instrument in writing under our, or
their, or one of their hands and seals, 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 immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Joseph Warren Zambra, on behalf of
myself and the said Henry Negretti, do hereby declare the nature of our
said 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 Drawing hereunto annexed, and to the letters
and figures marked hereon (that is to say) :-
Our Invention of "Improvements in Thermometers" relates, first, to
that class of instruments known as mercurial minimum thermometers
.

page_text: and, second, to certain improvements in what are usually termed
"clinical" thermometers, or those used for medical purposes.
In mercurial minimum thermometers there is usually attached to the
graduated tube a short supplementary tube and bulb into which (after
the mercury in the graduated tube has sunk to the minimum point) any
excess of mercury will pass on an increase or rise in the temperature
taking place. Upon taking an observation, and resetting the instru-
ment, the mercury is to be run out of the supplementary bulb. It has
been found in practice that a portion of the mercury is liable to stick in
this supplementary bulb, and break off at the neck, so that a correct
observation cannot be taken.
The object of our first improvement is to remedy this defect, which is
done by dispensing with the small bulb, and substituting for it a chamber
terminating with a capillary tube, or elongating the small tube, and
drawing down the bore of this tube to a point.
Fig. 1 in the accompanying Drawing represents a minimum ther-
mometer constructed in this manner.
a, a, is the ordinary tube, and 6 is the supplementary tube or chamber
terminating with a capillary tube, as shewn at 6, this part of the box of
the supplementary tube being drawn down to a fine point.
When the supplementary tube is constructed in this manner the
mercury will have no tendency to stick to the end of the tube, as is now
the case, but will rather be repelled. This supplementary tube may
either be attached to the bulb behind or it may be placed in front of
the bulb, and between it and the indicating part of the tube.
Our second improvement relates to clinical or medical thermometers,
which, on being applied to the body of a person, will indicate whether
such person be in health or not.
The instrument is constructed on the principle that the body of a
healthy person should be at a given and well-known temperature, say
ninety-eight degrees. If therefore the body of any one exceeds that
temperature it will indicate a state of fever more or less acute. If on
the contrary, the temperature of the body be below the normal state it
will indicate a want of vital heat, and that the patient is in a low state
of health.

page_text: In carrying out our Invention we employ alcohol, colored fusal oil,
or creosote for the indicating column, as colored liquid is more easily
seen than the very fine column of mercury which has heretofore been
employed in instruments of this kind.
Clinical thermometers have usually been made with a tube having a
very fine bore, and graduated with a small portion of the thermometric
scale.
The tube in our improved instruments is made with a wide bore just
above the bulb or a narrowed elongation of the bulb, as shewn at Fig. 2,
such wide bore or elongation of the bulb being of sufficient length and
capacity to take the column of colored liquid up to that point of tem-
perature at which it is required to take the medical observation, say up to
ninety degrees. From this point, say ninety degrees of the thermometric
scale, the bore is gradually narrowed to a very fine one, so that from ninety
degrees up to, say, one hundred degrees, the instrument will be very
sensitive. At some point on the glass tube is made a mark which we
will call zero. This point, if compared with a thermometer, will be
about ninety-eight degrees, which is set to indicate the temperature of
good health. The tube is then graduated into arbitrary divisions above
and below this zero point, and the colored liquid by rising above or
falling below that point will indicate either a feverish or a low state
of health.
In constructing our improved instruments we prefer to use fusel oil
properly colored rather than alcohol, as fusel oil does not boil at so low
a temperature as water, and therefore should the instrument become
deranged by an air bubble getting into the bore it will only be necessary
to immerse the bulb in boiling water when the air bubble will be driven
into the air chamber above.
In order that observations may be taken with accuracy we adapt to
the outside of the graduated tube a sliding index c, Fig. 2, which the
observer can slide up or down the tube to the point where the column
of colored fusel oil has stopped. He may then remove the instrument
from the patient, and examine it at leisure.
Having now described our Invention of "Improvements in Thermo-
meters.” and having explained the manner of carving the

page_text: JOSEPH WARREN ZAMBRA. (L.S.)