IMPROVEMENTS IN THERMOMETERS, BAROMETERS, GAUGES, AND OTHER INSTRU- MENTS FOR ASCERTAINING AND REGISTERING THE TEMPERATURE, PRESSURE, DENSITY, AND SPECIFIC GRAVITY OF AERIFORM FLUIDS, AND LIQUID OR SOLID BODIES
Year: 1852

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, we, ENRICO
ANGELO LUDOVICO NEGRETTI and JOSEPH WARREN ZAMBRA, both of Hatton
Garden, in the City of London, Meteorological Instrument Makers, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date
at Westminster, the Eighth day of March, in the fifteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto us, the said
Enrico Angelo Ludovico Negretti and Joseph Warren Zambra, Her especial
license, full power, sole privilege and authority, that we, the said Enrico
Angelo Ludovico Negretti and Joseph Warren Zambra, our exors, admors,
and assigns, and such others as we, the said Enrico Angelo Ludovico Negretti
and Joseph Warren Zambra, our exors, admors, or assigns, should at any
time agree with, and no others, from time to time and at all times during the
term of years therein mentioned, should and lawfully might make, use,
exercise, and vend, within England, Wales, the Town of Berwick-upon-
Tweed, and in all Her Majesty's Colonies and Plantations abroad, and in the
Islands of Jersey, Guernsey, Alderney, Sark, and Man, our Invention of
"IMPROVEMENTS IN THERMOMETERS, BAROMETERS, GAUGES, AND OTHER INSTRU-
MENTS FOR ASCERTAINING AND REGISTERING THE TEMPERATURE, PRESSURE, DENSITY,
AND SPECIFIC GRAVITY OF AERIFORM FLUIDS, AND LIQUID OR SOLID BODIES;" in
which said Letters Patent is contained a proviso obliging us, the said Enrico
Angelo Ludovico Negretti and Joseph Warren Zambra, by an instrument in

page_text: writing under our hands and seals, or under the hand and seal of one of us,
particularly to describe and ascertain the nature of our said Invention, and in
what manner the same is to be performed, and to cause the same to be inrolled
in Her Majesty's High Court of Chancery within six calendar months next
and immediately after the date of the said in part recited Letters Patent, as
in and by the same, reference being thereunto had, will more fully and at
large appear.
NOW KNOW YE, that in compliance with the said proviso, we, the said
Enrico Angelo Ludovico Negretti and Joseph Warren Zambra, do hereby
declare that the nature of our said Invention, and the manner in which the
same is to be performed, is particularly described and ascertained in and by
the following description thereof, reference being had to the Drawings
hereunto annexed, and to the letters and figures marked thereon (that is
to say) --
This Invention of "Improvements in Thermometers, Barometers, Gauges, and
other Instruments for ascertaining and registering the Temperature; Pressure,
Density, and Specific Gravity of Aeriform Fluids and Liquids, or solid Bodies,"
relates, first, to an improved mode of making registering thermometers, and
consists in choking, or diminishing, or partially closing the bore of the tube at a
certain point, by preference near the bulb, or at any other convenient point that
may be considered more desirable. This choking of the tube or partially closing
the bore may be effected by placing a short piece of wood, glass, or platinum
or other wire, or suitable material in the bore, or by merely bending or twisting
the tube so as partially to close the same, which should be effected to such an
extent that although the mercury will pass when under pressure by the
expansion of the fluid or metal in the bulb, occasioned by an increase of
temperature, yet upon the temperature diminishing the mercury will not, as is
usually the case, pass again into the bulb until force is applied. The column
of mercury or fluid that has by expansion been driven along the tube will
therefore remain stationary, and will consequently indicate the maximum
temperature to which the thermometer has been subjected. It should be
observed that a vacuum is created in the tube of the thermometer above the
column of mercury, and consequently when the mercury by expansion has
reached any given point in the tube it will always remain there until it is
intentionally removed, whereas if the upper part of the tube contained air, the
latter would have a tendency to force back the mercury when the pressure
occasioned by the expansion is withdrawn. In the accompanying Drawings
we have shewn two methods of carrying out this part of our Invention. Fig. 1
represents in elevation a maximum thermometer constructed according to our

page_text: improvements. In this instance the choking or partially closing the tube is
effected by inserting a piece of wood, glass, or wire in the bore of the tube
near the bulb, and then bending the tube so as to form nearly a right angle.
The thermometric scale is made exactly in the same way as in ordinary ther-
mometers, but sometimes instead of making it on the wood or metal plate, as
shewn in Fig. 1, we engrave the scale on the glass tube itself, for the purpose
of insuring greater accuracy; and in order that the degrees and figures may be
more legible on the scale we make the tube flat, as shewn in Fig. 2, instead of
round as is usually the case. This mode of constructing glass thermometers
of flat glass tube we also apply to the manufacture of ordinary glass chemical
thermometers, as shewn in Fig. 3. Fig. 2 also represents another method of
making our improved maximum thermometers. In this instance the tube is
flat instead of round, and the choking or partial closing of the bore of the tube
is produced by twisting the tube near the bulb, when warm, instead of insert-.
ing some substance in the bore.
The second part of our Invention relates to water gauges, and is intended to
ascertain and indicate the density of water in steam boilers. This improve-
ment consists in the adaptation of a thermometer, which by indicating the
difference of temperature of the water at different densities will effect the
The bulb of the thermometer is inclosed in a small chamber, cup;
purpose.
cistern, or vessel, into which water from the boiler may be made to flow
through a branch pipe and connection. It is well known that pure water
under atmospheric pressure boils at a temperature of two hundred and twelve
degrees Fahrenheit; but when water holds any body, such as salt or calcareous
matters in solution, it will not boil until it rises to a much higher temperature.
The scale of the thermometer attached to this instrument can therefore be
made to indicate the dangerous points above which it would not be safe to
evaporate the water for generating steam. It will therefore be evident that if
the water when drawn from the boiler and left merely under atmospheric
pressure indicates on the thermometric scale a degree of temperature above a
certain point marked upon that scale, then the engineer will know with
certainty, and by a simple examination of the instrument, that the water in the
boiler is too highly charged or impregnated with salt or other matters, and must
therefore be blown off until the specific gravity of the water is reduced to a safe
point. Fig. 4 is a front elevation, and Fig. 5 a longitudinal vertical section of
one of our improved gauges, which is connected to the boiler by a screw
coupling in the same manner as steam, or pressure, or water gauges are
usually connected. The short tube c, to which the coupling is attached, is
furnished with a stopcock d, and the other end of the tube c enters or is con-

page_text: nected to a small open chamber, cup, cistern, or vessel e, into which steam and
water from the boiler can be admitted by opening the cock d; a small open
overflow pipe f, Fig. 4, is attached to one side of the cistern, cup, chamber, or
vessel e, and when it is required to ascertain the density of the water in the
boiler, it will only be necessary to turn the stopcock d for a few seconds, in
order to allow a small quantity of water to enter the cistern or vessel, and then
the thermometer g will indicate the temperature of the water, which if above
a certain point, marked "dangerous" on the scale, will give notice to the
engineer that some of the dense water should be blown off. It should be here
observed, that as the water from the boiler, when allowed to flow into the
metal cup, cistern, or vessel outside, will be somewhat reduced in temperature,
and would consequently give false indications, it will be found advisable to
allow the water from the boiler to flow through the instrument and out of the
overflow pipe f for a minute or so before examining the scale, in order to raise
the temperature of the instrument to that of the water in the boiler. When
the instrument is brought to the same temperature as the water, which will be
seen at once by the mercury in the thermometer tube remaining stationary at
a certain point, then the stopcock d should be closed and the observation
made, after which the cup, cistern, or vessel e may be emptied by simply
opening the stopcock h and allowing the water to run out at bottom. It is
evident that two, three, or more of these instruments can be placed in different
parts of the vessel, as, for instance, in the captain's, chief officer's, and head
engineer's cabins, and being connected with the boiler by a tube, these officers
can at any time ascertain the density of water in' the boiler, and give orders
accordingly.
The next part of our Invention relates to improvements in the construction
of barometers, and has for its object, firstly, the construction of an improved
pocket barometer, which consists principally of a vacuum thermometer tube,
with an elastic or 'flexible bulb, made of glass, platinum, hörn, tortoiseshell,
platinized silver, or other thin flexible metallic or other substance. The
external air by pressing on the elastic bulb which contains mercury or other
liquid material will force the latter up the vacuum tube and indicate the
amount of the pressure of the atmosphere,' 'due allowance being made, as in
ordinary pocket barometers, for the expansion of the mercury by changes in
the temperature of the atmosphere. In the Drawings, Fig. 6 .represents a
front elevation of the 'most simple form of a pocket barometer, constructed
according to our improvements. "In this instance a simple thermometer
tube i is employed. A vacuum is made therein above the mercury, and the
bulb j being made flat and of thin glass is sufficiently yielding or flexible to be

page_text: acted upon by the changes in the pressure of the atmosphere, so as to indicate
these changes very visibly on the scale by the rising of the mercury or fluid in
the tube. A common thermometer tube and scale m are placed beside the
barometric tube i, for the purpose of indicating the temperature of the atmo-
sphere, so that allowance may be made for the expansion of the mercury by
means of the sliding scale n when taking a barometric observation. In the
instrument shewn in the Figure a mean temperature of sixty degrees Fahren-
heit is assumed, and the instrument is set to shew the pressure of the atmo-
sphere at that temperature; but if the temperature increases or diminishes,
then the scale n must be slidden up or down, until the index point 1 is brought
opposite the degree marked on the scale o to correspond to the indications of
the thermometer m. Fig. 7 is a sectional representation of another method of
carrying out this improvement. In this case a thermometric tube i is screwed
to a metal box, furnished with a thin flexible bottom p, made of platinized
silver, tortoiseshell, or any other suitable material, such as those above
mentioned. Fig. 8 is a longitudinal section, and Fig. 9 a transverse section
of another method of making the flexible reservoir for the mercury. 9, q, is a
rectangular wooden or metal frame, covered on both sides with a thin sheet of
platinized silver or other suitable material, which must be well secured to
the frame q, so as to prevent leakage of the mercury. r, r, are two brass or
other metal plates which are secured to the frame by bolts or screws, which
pass through as seen in the Figures. One or more holes are made in the plates
r, r, to allow the atmosphere to act or press on the thin flexible sheet of
platinized silver or other material. In all these cases the atmosphere acts on
the flexible part of the cistern, and causes the mercury or other fluid to rise
and fall in the tube and indicate the pressure.
Our second improvement in barometers relates to a novel mode of construct-
ing a self-registering barometer, and consists in placing small tubes or
reservoirs by the side of and parallel with the ordinary barometer tube; one
of these small additional tubes or reservoirs should be placed at the upper, and
the other at the lower part of the main barometer tube, with which they are
both made to communicate by lateral tubes. These additional tubes or reser-
voirs are furnished with indexes, and, as the mercury flows into and rises and
falls in these lateral tubes, the indexes which are contained therein are raised
or lowered accordingly, and will thereby indicate the highest and lowest
point of pressure of the atmosphere within a given time. Fig. 10 is a front
elevation of one of our improved self-registering barometers. s is the main
barometer tube, which is closed at top, and is turned up and forms a syphon

page_text: below somewhat similar to the tube of an ordinary syphon barometer; t is a
side tube connected at top and bottom, by short lateral tubes, with the upper
part of the main barometer tube; and u is a similar side tube connected at
top and bottom, by short lateral tubes, with the lower end or syphon part of
the main barometer tube. The upper end of the syphon tube, and also the
upper end of the tube u, are of course open to the influence or pressure of the
atmosphere, although shewn in the Drawing as covered up to keep out dust or
extraneous matters. Each of the side tubes t and u are furnished with metal
indexes 2 and 3, which will indicate the highest and lowest pressure that has
been exerted by the atmosphere within a given time. For instance, when the
pressure of the atmosphere increases it will cause the mercury to rise in the
main tube s, and also in the side tube t, and thereby force up in the latter the
index 2; if, on the contrary, the pressure of the atmosphere should diminish,
then the mercury' will rise in the syphon part of the main tube, and also in the
side tube t, in which latter it will push up the index 8, and thereby indicate
the lowest amount of pressure. The barometric scale for the main tube is
made in the ordinary manner, but for the two side tubes the length of the
column of mercury is divided into two portions, and the scales for both side tubes
commence from the central line, as in the ordinary syphon barometer.
The last head of our Invention relates to instruments for measuring or
ascertaining the specific gravity of liquids by means of their expansion at cer-
tain degrees of temperature. The form or construction of instrument which
we prefer for effecting this object, and have found practically to answer the
purpose, is shewn at Figures 11 and 12. It consists of a reservoir, cistern, or
vessel composed of three principal parts a, b, and c. This reservoir or vessel
is made of thin metal, such as thin sheet brass, copper, silver, or other metal,
and is constructed in such a manner as to expose a large surface; the part a
forms the upper chamber of the reservoir, and is furnished with a socket d,
into which is fitted a glass tube c, of small bore and open at top, and to which
is adapted a graduated scale f; the scale f and tube e are enclosed in a larger
glass tube to protect them from injury or derangement. The part b, b, of the
reservoir, cistern, or vessel consists of two hollow columns, which connect the
upper part or chamber a to the lower part c, which is furnished with a stop-
cock g, whereby the reservoir or vessel is filled or emptied. The part c also
carries a socket, into which is fixed the tube of a thermometer h, the bulb of
which is enclosed in the chamber c of the reservoir. The instrument is used
in the following manner:-A sufficient quantity of the liquid to be tested is
poured into a tall vessel, in which the instrument is to be slowly immersed, the

page_text: stopcock g having been previously opened in order to allow the parts a, b, c, of
the reservoir, and also part of the tube e, to fill with the liquid to be examined.
Upon closing the stopcock it will perhaps be found that the liquid extends
some way up the tube e, it must therefore be carefully adjusted to the zero
point by opening the stopcock and allowing some of the liquid to run out until
the surface thereof reaches zero on the scale; but previous to this adjustment
the instrument must be immersed in a vessel containing water at sixty-two
degrees Fahrenheit, so as to bring the instrument to that temperature; after
adjustment at 62° it must be taken out and quickly immersed in another vessel
containing water at ninety-two degrees Fahrenheit, thereby raising the tempera-
ture thirty degrees, then the amount of expansion of the liquid in the reser-
voir a, b, c, will be indicated on the graduated scale, which will at once shew
the alcoholic strength, if spirits, or specific gravity of any other liquid. The
graduated scales of these instruments must be made by experiment, as every
instrument will vary in some slight degree from others; we will, however,
describe a plan which will be found convenient for making these scales, but we
do not intend to confine ourselves thereto; zero is an arbitrary point, and
merely means the point at which distilled water at sixty-two degrees, or any
other point of Fahrenheit, will stand on the scale. Having filled the instru-
ment with this water and marked the zero point, immerse the instrument in
water at ninety-two degrees, and mark off the expansive temperature, and call
it one hundred. Then take some alcohol, well ascertained to be, say sixty
degrees overproof, and, having emptied out the water, fill the instrument to
zero with this liquid, and, after raising the temperature of the alcohol to ninety-
two degrees in the manner already explained, carefully mark off the point 60°;
then take other strengths of alcohol, vizt, at fifty, forty, and so on overproof
down to proof, and proceed in the same manner, and mark these points on the
scale, using the letter P for proof; then proceed with other and weaker solu-
tions, that is, those under proof, down to ninety degrees under proof, and then
the scale will be complete, and will indicate correctly the alcoholic strength
of any liquid of any specific gravity between distilled water and alcohol sixty
degrees overproof. We would here observe that although we have stated
that the examination of liquids to ascertain their specific gravities should be
made between the temperatures of sixty-two degrees and ninety-two degrees
of Fahrenheit's thermometer, yet other limits may be employed. We, how-
ever, prefer those set forth, as in practice we have found them the most
convenient.
Having now described our several improvements, and the best means with

page_text: which we are at present acquaintedi for carrying, the same into effect,, we would
observe in conclusion that we do.not intend to confine, ourselves to the. precise
arrangement and construction of parts: herein. shewn and described, as. they
may, doubtless, be varied, in some particulars: without. departing from the
nature and object of our Invention;: nor do we intend to claim the exclusive
right to all the parts of the several instruments above described and set forth,
as some parts: may have been heretofore applied to.similar uses; but that which
we consider to be.new. in the above-described improvements, and therefore wish
to claim as the Invention, secured to us by the herein-before in part recited
Letters. Patent, is
First, making a registering maximum thermometer or instrument to indi-
cate and register the maximum temperature to which it may be submitted, in
the manner herein-before set forth and described; that, is,. by choking or
partially closing the bore of the tube at any convenient place, so that when,
by expansion by reason of an increase of temperature, the mercury. or indicating
liquid may be forced beyond this: point; it will not return of itself into. the bulb,
as in ordinary thermometers, but will: remain stationary in the tube until
removed therefrom. by some external. agency. We particularly claim the
choking or partially, closing thermometer: tubes to effect this purpose, by
whatever means: such choking or partial closing of the tube may be produced.
Second, as regards water gauges, we claim the instrument above shewn,
or any mere modification thereof, in which the density of water, or liquids more
dense than water, (or in other words the amount of salt or other matters it or
they may hold in solution or suspension,) may be known and indicated by
ascertaining the temperature of such liquid or liquids at or above the boiling
point, such instrument, being founded on the principle that liquids at different
densities boil at: different. degrees of temperature when under atmospheric
pressure.
Third, we claim constructing pocket barometers with a vacuum tube of a
shorter length than the ordinary Torricellian tube, such tube being furnished
with a flexible bulb or cistern, so that the pressure of the atmosphere may act
thereon, and cause the mercury to rise and fall in the tube, as shewn and
:described. And further, in reference to registering barometers, we. claim the.
suse of the lateral or side tubes or reservoirs, to which indexes may be applied
to shew and register the highest and lowest points to which the mercurial
column may be made, by the variation in the pressure of the atmosphere, to rise
and fall within any given time.
Fourth, we claim the instrument above shewn and described, or any mere

page_text: nodification thereof, for ascertaining the specific gravity of liquids by their
expansion under a given increase of temperature.
In witness whereof, we, the said Enrico Angelo Ludovico Negretti and
Joseph Warren Zambra, have hereunto set our hands and seals, this
Eighth day of September, in the year of our Lord One thousand
eight hundred and fifty-two.
JOSEPH WARREN (L.s.) ZAMBRA.
AND BE IT REMEMBERED, that on the Eighth day of September,
in the year of our Lord 1852, the aforesaid Enrico Angelo Ludovico
Negretti and Joseph Warren Zambra came before our said Lady the Queen
in 'Her Chancery, and acknowledged the Specification aforesaid, and all and
every thing therein contained and specified, in form above written. And also
the Specification aforesaid was stamped according to the tenor of the Statute
made for that purpose.
Enrolled the Eighth day of September, in the year of our Lord One
thousand eight hundred and fifty-two.