AN IMPROVEMENT ON THE AIR BAROMETER, WHICH IMPROVED INSTRUMENT IS TO BE CALLED A SYMPIESOMETER
Year: 1818

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER,
ADIE, of the City of Edinburgh, Optician, send greeting.
WHEREAS His present most Excellent Majesty King George the Third.
did, by His Royal Letters. Patent under the Great Seal of the United
Kingdom of Great Britain and Ireland, bearing date at Westminster, the
Twenty-third day of December, in the fifty-ninth year of His reign, give and.
grant unto me, the said Alexander. Adie, my executors, administrators,' and
assigns, His especial licence, full power, sole privilege and authority, that,
I, the said 'Alexander Adie; my executors, administrators, and assigns, during
the term of years therein expressed, should and lawfully might make, exercise,
and vend, my Invention of." AN IMPROVEMENT ON THE AIR BAROMETER, WHICH
IMPROVED INSTRUMENT IS TO BE CALLED A SYMPIESOMETER," within England;
Wales; and Berwick-upon-Tweed, in such manner as to me, the said
Alexander Adie, mý executors, administrators, and assigns, should in our
discretion seem meet; in which said Letters Patent is contained a proviso
that if I, the said Alexander Adie, should not particularly describe and
ascertain the nature of my 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 His Majesty's High Court of Chancery,
within two calendar months next and immediately after the date of the said
Letters Patent, that then the said Letters. Patent, and all liberties and advan

page_text: tages whatsoever thereby granted, should utterly cease, determine, and become
void, as in and by the said recited Letters Patent, relation being thereunto had,
may more fully and at large appear..
NOW KNOW YE, that in compliance with the said proviso, I, the said
Alexander Adie, do hereby declare that the nature of my said Invention, and
in what manner the same is to be performed, are particularly described and
ascertained in manner following (that is to say):-
The object for which I claim a Patent is an improvement on the air
barometer, which I call a Sympiesometer; and my Invention consists in
employing an elastic fluid or gas different from air, and any liquid, except
quicksilver, which neither acts upon the gas which it confines nor is percep-
tibly acted upon by the air, to the contact of which it is in some measure
exposed. Hydrogen gas, azotic gas, or any of the gases not liable to be
absorbed by the inclosing fluid, may be used, but I prefer and employ hydrogen
gas. The liquid which answers best is any unctuous oil, or mixture of
unctuous and volatile oils. I prefer and employ almond oil, covered with
anchusu root. The form and construction of the sympiesometer are as
follows: 1st. It consists of a tube of glass of any length or diameter; I prefer
one about eighteen inches long and 07 of an inch diameter inside, terminated
above by a bulb about two inches long and half an inch in diameter (but this
will vary as the instrument is required to have a greater or lesser range), and
having the lower extremity bent upward, and expanding into an oval cistern
open at top. The bulb at the upper end is drawn to a slender thread, and at
first is left open. To introduce the gas and oil I fill the bulb and tube with
quicksilver, and close the mouth of the cistern with my finger; a communi-
cation is then formed between a gasometer containing the gas to be used, and
the slender pipe at the end of the bulb by means of a flexible tube, and the
orifice of the cistern being then opened the quicksilver flows out till it descends
in the tube to the level of the top of the cistern, and the gas enters to supply
its place. The slender pipe is then to be sealed hermetically close to the bulb
by the touch of the flame of a blow pipe. The tube is now to be inverted,
and the mercury poured out of the cistern, allowing the column which occupies
the tube to run towards the bulb, to prevent the escape of the gas; the tube
being again turned upright, the portion of quicksilver which remains is
removed by pouring some of the oil over it, and heating the gas until by
its expansion it forces the column of quicksilver which is left at the lower
end of the tube into the cistern, then holding the tube nearly horizontal,
the oil will enter as the gas cools, and the remaining quicksilver may be
poured out of the cistern. The gas introduced changes its bulk, or occupies

page_text: more or less space, according to the pressure of the atmosphere upon the surface
of the oil in the cistern. The scale for measuring the change in the bulk of the
gas occasioned by a change of pressure is formed experimentally by placing
the instrument in an air-tight glass case, along with an accurate barometer
5 and thermometer. The glass case is furnished with a condensing and exhausting
syringe, by which any density may be given to the enclosed' air, so as to sup:
port a column of quicksilver in the barometer of 28, 29, 30, or any other
required number of inches. The height of the oil in the tube of the sym-
piesometer corresponding to these points being marked on its scale, and the
spaces between being divided into a hundred parts, these parts correspond with
hundredths of an inch on the scale of the mercurial barometer. As the bulk
of the gas is altered by any change that takes place in the temperature of
the atmosphere, it is necessary to apply a correction on this account. For this
purpose the principal or barometric scale is made to slide upon another
scale, which is divided into degrees and parts so as to represent the changes
of bulk in the gas produced by a change of temperature under the same
pressure, and corresponding to the degrees of a common thermometer attached
to the instrument. This scale is constructed in the same manner as the scale
of a common thermometer, by changing the temperature of the bulb while the
pressure is the same, and noting the range of the oil occasioned by it. In
using the instrument observe the temperature of the thermometer, and set the
index which is upon the sliding sympiesometer scale opposite to the degree of
temperature upon the fixed scale, and then the height of the oil, as indicated
on the sliding scale, will be the pressure of the air required. When the height
of one place above another is to be measured by the diminution of the
pressure of the atmosphere, another correction is necessary to insure perfect
accuracy in all instruments indicating this change, because the pressure of a
column of air of a given altitude varies according to its humidity or moisture.
Another of my improvements connected with the sympiesometer consists in
the invention and application of a new hygrometer, which may either be
attached to the instrument or used separately. This hygrometer is constructed
of the fine internal film or membrane which lines the hollow tube of the
arundo phragmites. A small bag made of this membrane is filled with quick-
silver, and attached to the lower end of a thermometer tube, so as to form as it
were its bulb. The quicksilver in the bag occupies part of the glass tube,
and rises and falls by any change of humidity, which is indicated upon a scale
attached to the tube. The lower end of the glass tube, instead of being merely
inserted in the top of the bag, may pass through it, the quicksilver in the bag
communicating with that in the tube by an opening made in the side of the
:

page_text: tube. By this means the bag is supported by the glass tube, and prevented
from being injured by any slight accident, and the instrument is less affected
by any change of temperature. The hygrometer may be also made in the
same manner as Saussure's, by substituting a slip of the membrane already
mentioned in place of the hair employed by the philosopher. In some of my
sympiesometers the scale is divided into parts corresponding to the increase in
bulk which takes place in the gas by the diminished pressure of the atmo-
sphere on ascending a given height, the temperature being 32° of Fahrenheit.
This scale is also formed by experiment as follows:-The instrument being
placed in the glass case as before described, increase the density of the
inclosed air until it support a column of quicksilver of 31 inches, the tempe-
rature, being 32°; mark this point zero. Then to the logarithm of 31 add
0100, and find the corresponding number, which is 30 294, regulate the
density of the air to support a column of quicksilver of this length, number
this point on the scale 100, and divide the space into a hundred parts, each
part will equal the increase of bulk or fall of the oil in the tube by ascending
one fathom, the ordinary correction being allowed for any change of tempe
perature in the atmosphere. In the above manner proceed. by adding ⚫0100
to the logarithm last found, and marking the points corresponding to these
densities, until the scale is complete. By subtracting the number of fathoms
indicated by the spmpiesomèter at the under station from that indicated at
the upper station the difference will be the number of fathoms which the one
place is above the other.
In witness whereof, I, the said Alexander Adie, have hereunto set my
hand and seal, the Thirteenth day of February, in the year of our Lord

page_text: Improvement on the Air Barometer, which improved instrument is to be called
a Sympiesometer. And this Deponent further maketh oath and saith, that the
name or character "Alex" Adie," set at the foot of the said Deed Poll, as
the Party executing the same, is of the proper handwriting of the said
Alexander Adie, and that the names or characters "John Dunn and John
McDonell" indorsed on the said Deed Poll, as Witnesses to the signing and
sealing thereof, are of the respective handswriting of this Deponent and John
McDonell, Optician, also of the City of Edinburgh.
AND BE IT REMEMBERED, that on the Affidavit of the said John
Dunn, the Instrument aforesaid was inrolled, word for word, as above written.
And also the Instrument aforesaid was stamped according to the tenor of
the Statute made in the fifty-fifth year of the reign of His Majesty King
George the Third.
Inrolled the Sixteenth day of February, One thousand eight hundred and
nineteen.