AN IMPROVEMENT IN THE CONSTRUCTION OF HYDROMETERS
Year: 1802

page_text: R'S
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
SPEER, of the City of Dublin, Esquire, send greeting.
WHEREAS His most Excellent Majesty King George the Third, by
His Letters Patent under the Great Seal of Great Britain, bearing date
at Westminster, the Second day of August, in the forty-second year of His.
reign, did give and grant unto me, the said William Speer, my executors,
administrators, and assigns, special licence, full power, sole privilege and
authority, that I, the said William Speer, my executors, administrators, and
assigns, during the term of years therein expressed, should and lawfully might
make, use, exercise, and vend the Invention therein-mentioned, to wit, "AN
IMPROVEMENT IN THE CONSTRUCTION OF HYDROMETERS," within that part of the
United Kingdom of Great Britain and Ireland called England, the Dominion of
Wales, and Town of Berwick-upon-Tweed, in such manner as to me, the said
William Speer, my executors, administrators, and assigns, should seem meet,
to have, hold, receive, and enjoy the said licence, powers, privileges, and advan-
tages therein granted or mentioned to be granted unto me, the said William
Speer, my executors, administrators, and assigns, for and during and unto the full
end and term of fourteen years therein expressed; in which said Letters Patent
there is (amongst other things) contained a proviso that if I, the said
William Speer, should not particularly describe and ascertain the nature of

page_text: the said Invention, and in what manner the same is to be performed, by an
instrument in writing under my hand and seal, and cause the same to be
inrolled in the High Court of Chancery within six calendar months next and
immediately after the date of the said Letters Patent, that then the said
Letters Patent, and all liberties and advantages whatsoever thereby granted,
should utterly cease, determine, and become void, as in and by the said
Letters Patent, reference being thereunto had, may more fully appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
William Speer, do hereby describe and ascertain the nature of my said
Invention and improvement, and the manner in which the same is to be
performed, that is to say:-
I construct my hydrometer as usual of a ball or hollow metallic part, to
which is affixed a short stem with a load or weight, and diametrically opposite
a longer stem, for the purpose of graduation. The figure and dimensions of
those several parts may be varied according to the well-known principles of
this instrument, but the peculiar advantages of my improvement consists in
the figure and method of graduating the stem, by means of which the
gradations of strength of spirits at any known temperature can be seen
at once by immersion of the instrument without the necessity of changing
weights by trial, or making any computations, or referring to any tables or
sliding rule, or other instrument whatever. I accomplish these purposes by
constructing the upper stem in the form of a polygonal prism of such dimen-
sions that the whole of the said stem shall float above the surface of water at
the temperature of thirty-five degrees of the thermometer of Fahrenheit, and
.the surface of the water shall intersect the lowest line of graduation upon one
of the faces of the prism, and upon the said face I mark lines of graduation
at the several stations to which the instrument has been found to be immersed,
and to float in known mixtures of water and ardent spirit of different
strengths, at the temperature of thirty-five degrees aforesaid above or under proof
up to the strongest which can by produced by distillation, and I mark the
said graduations on the stem by numbers denoting the ultimate results
or strengths commonly known by the term per-centages, which said
.results have heretofore been ascertained by computation instead of direct
inspection, as is done by the instrument with my improvement. And
farther, in explanation of the term per-centage, I here observe that a
'spirituous liquor is said to be ten per cent. or any other given quantity over
: hydrometer proof, when it is so strong that one hundred gallons of the said
spirit will admit of an addition of ten gallons of water to reduce it to the
.strength of proof; and it is said to be ten per cent. under proof when one

page_text: hundred gallons of the spirit contains ten gallons more of water that the
same quantity of proof spirit contains. And lastly, I engrave at the upper
end of the said face the figures 35, to denote that the graduations on that
face of the prism are applicable to spirits at that temperature or number of
degrees. And, moreover, upon the next contiguous face of the prism I form
and apply by the means aforesaid a similar graduation for an higher tempera-
ture, such for example as the temperature of forty degrees; and again
upon the face or side next contiguous to the last-mentioned face or.
side, I form and apply a similar graduation for a still higher temperature,
such for example as the temperature of fifty degrees; and in this
manner I graduate the several faces of my stem, so that the face last
graduated shall be applicable to the highest ordinary temperature, as for
example seventy degrees. The number of sides of the polygon may be
greater or less according to the number of temperatures respectively to which
the determinations are required to be made, but I adopt and recommend eight
sides as the best adapted for the general purposes of revenue and commerce,
so that each side shall bear a scale of per-centages of spirit differing in
temperature by five degrees, namely, beginning at 35 degrees and ending at
70 degrees; and to prevent any error which might possibly arise from an
unskilful operator reading off the strength upon a wrong face of the instru-
ment, I apply to the stem a small index, which embraces the same, and can be
slided upwards and downwards to any part thereof, so as to point at the proper
division. This index, which is of a different colour from the stem itself, con-
stitutes part of the weight of the instrument above the fluid, but it is by no
means a trial weight, for it is put on from the indication of temperature before
the instrument is immersed at all; and farther, although it is very easy, from
the contiguity of the divided faces for each temperature upon the eight-sided
instrument, to read the result for the intermediate temperatures to a degree of
precision fully adequate to the purposes of revenue and trade, I do nevertheless
make and apply, as an addition to the said improved instrument (to be used or
not at the pleasure of the operator), two other indexes which, being lighter
than the first-mentioned index, do cause the instrument to shew the strengths at
two equal intermediate temperatures between those marked upon any contiguous
face of the general scale; thus, for example, supposing the temperature to be
fifty degrees, nothing further would be required but to place the index No. 1
on the side marked fifty, & immerse it in the fluid, of which it will at once
shew the strength; but if the temperature be 51 or 52, I use the next lighter
index, marked No. 2, which will cause the graduations to indicate strengths
for the temperature 51°; or in case the temperature had been 53 or 54, then

page_text: the index No. 3 would have been to be applied, and the said face would then
indicate strengths for the temperature 53, so that the result by the instru-
ment will be true for the intermediate temperatures within half a degree, and
even this small difference, if attended to or thought of any importance, may
be obtained by holding the jar containing the spirit a few moments in the
hand. And in the construction of an instrument for the immediate purposes
of revenue and trade, I do recommend, and in practice make, the graduations
on the stem to comprehend only those per-centages or strengths which are
met with in the spirits usually dealt in. In commerce, instead of beginning
my graduations as low as water, near which strength no spirits are made, sold,
or of carrying the said graduations up to the very highest alcohol, which is
comparatively an article of little sale or transfer, by which means I render
my instrument more convenient and the divisions more open and clear. And
with regard to the higher or lower strengths, I would recommend another
stem to be applied to the same instrument as herein-after described. And
lastly, in this my new improvement of the hydrometer, and the method of
graduating the same, since I do not confine myself to the number of sides
in the prism or stem, but make them as numerous as the intended precision of
experiment may require, I do also apply the same method of graduation to
a cylindrical stem which (as mathematicians well know) may be considered
as a prism with an infinitely great number of sides. In this construction my
lines of division, beginning from the lowest point (as for water at thirty-five
degrees), are passed obliquely upwards round the stem, and intersect certain
straight lines drawn at equal distances from each other up the stem, which by
their intersection with the former obique lines, afford certain points of gradua-
tion which answer to the several temperatures. And by this means, when the
temperature is known, the immersion of the instrument will show by the
intersection of the surface of the fluid, and one of the oblique lines on the
very line of that known temperature, what may be the strength of the spirit
or otherwise. I make the stem of any figure whatever of equal dimensions
throughout its length, and instead of the flat sides of a prism I divide the
surface into longitudinal compartments by lines drawn lengthways thereon, and
I make my several scales of graduation as herein-before described within and
upon the said several compartments; and in all the before-mentioned construc-
tions wherein the same may be thought necessary or desirable with regard to
the intermediate degrees (instead of using different indexes as aforesaid), I
alter the weight of the instrument before immersion by inserting four small
pins in holes in the load or counterpoise below, or, if preferred, in the top of
the upper stem, one of which pins being taken out causes the instrument to

page_text: become lighter for one of the intermediate degrees of temperature, and two
of the said pins being taken out produce a change answerable to two degrees
of temperature.
Having, as above, described the use and application of my Invention to
the ascertainment of the degrees or per-centages of the strength of spirits, at
the temperature of from thirty-five to seventy, both inclusive, I now proceed
to shew by what variation of my hydrometer the degrees of strength greater or
less than those above mentioned may be ascertained. And this I accomplish
in the following manner, that is to say, from forty per cent. over proof at the
temperature of 55 or thereabouts, up to alcohol or pure spirit, I use a short
stem instead of that above described; which I remove on this occasion,
screwing on the latter in it's stead, and which, being lighter, the immersion of
the instrument is diminished, and thereby adopted to the shorter stem, and on
this short stem I mark the different gradations or per-centages of strength in
like manner as I have herein-before mentioned in relation to the other stem,
and which being duly attended to no further description is necessary. In like
manner I adopt the instrument to the ascertainment of the strengths of spirits
of a weaker quality than those first above-mentioned, by putting on a longer
stem instead of that first described, and by graduating such longer stem so as
indicate the gradations or per-centages of strength of the spirit to be examined;
and in order to prevent evasion in the two last-mentioned cases, I think it
proper to add, that though I have mentioned a shorter and longer stem,
yet the same purposes may be answered by using in the one case a lighter
instead of shorter stem, and, in the other by using a heavier instead of a
longer stem.
In witness whereof, I, the said William Speer, have hereunto set my
hand and seal, this First day of February, in the year of our Lord
One thousand eight hundred and three, and in the forty-third year
of the reign of our Sovereign Lord George the Third, by the grace
of God of the United Kingdom of Great Britain and Ireland King,
Defender of the Faith.

page_text: AND BE IT REMEMBERED, that on the same First day of February, in
the year above mentioned, the aforesaid William Speer came before our Lord
the King in His Chancery, and acknowledged the Specification aforesaid, and
all and every thing therein contained, in form above written. And also the
Specification aforesaid was stamped according to the tenor of the Statute
in that case made and provided.
Inrolled the same First day of February, in the year above written.