A NEW CONSTRUCTED INSTRUMENT BY WHICH IS SHEWN THE TRUE EFFECT OF THE WEIGHT OF THE ATMOSPHERE, WITH THE VARIATION WHICH IS CAUSED BY THE HEAT AND COLD, AND LIKEWISE THE QUANTITY OF THAT VARIATION
Year: 1765

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
PYEFINCH, of Cornhill, London, Optician, send greeting.
WHEREAS I, the said Henry Pyefinch, together with John Hyacinth
de Magalhaens, of Cornhill aforesaid, Gentleman, did, by petition to the
King's most Excellent Majesty, humbly shew that we had found out and
brought to perfection "A NEW CONSTRUCTED INSTRUMENT BY WHICH IS SHEWN
THE TRUE EFFECT OF THE WEIGHT OF THE ATMOSPHERE, WITH THE VARIATION
WHICH IS CAUSED BY THE HEAT AND COLD, AND LIKEWISE THE QUANTITY OF THAT
VARIATION; and therefore, as well as for other reasons contained in the said
petition, did pray His said Majesty to grant unto us His Royal Letters
Patent for the sole use and benefit of the said Invention within that part
of Great Britain called England, Dominion of Wales, and Town of Berwick-
upon-Tweed, and also within His Majesty's Plantations and Colonies abroad,
for the term of fourteen years; to the prayer of which petition His said
Majesty was most graciously pleased to condescend, and Letters Patent
agreeable thereto have accordingly passed the Great Scal.
NOW KNOW YE, that I, the said Henry Pyefinch, in compliance and
in performance of a provisoe or condition contained in the said Letters
Patent, do hereby describe and ascertain the said Invention in manner
following, viz
-
1st. Instead of a simple Torricellian tube, we make use of one bent, or in
form of a siphon, for this instrument.
2d. The inside of this siphon is to be exactly measured by any method
able to settle the capacity of its bore, and account for the different sizes
thereof, which may be done by pouring therein a certain quantity of quick-
silver, adding as often thereto the same quantity till the whole be filled,
making at each time the space occupyed thereby.

page_text: 3d. To observe in temperate weather, viz', at fifty-five degrees of Faberen-
heit's scale, the true bulk of the quicksilver which is necessary for the filling
the siphon, and settle every different altitude of the various mercurial columns
that may happen throughout the year (viz₁, from twenty-seven or twenty-
eight inches to thirty-one, according to the tubes inside, which will be known
by the second article.
4th. To make very exact observations with such siphon in all the different
temperaments of the weather, and to calculate upon them all the different
degrees of the various heighths of the mercurial columns already settled by
article 3, which numbers of the degrees must be marked in an inverse order
(viz), directly down upon the short leg, and inversly right up in the long leg,
always keeping the true mean temperate bulks of the places where are
marked the numbers belonging to the longest leg.
5th. To examine with a good hydrostatical ballance what is the true specific
weight of a cubic inch of the quicksilver contained in each siphon.
And I, the said Henry Pyefinch, do hereby averr and declare, that the
above is a true, full, and perfect description of the nature and practice of the
Invention.
In witness whereof, I, the said Henry Pyefinch, have hereunto set my
hand and seal, the Twenty-fourth day of July, One thousand seven
hundred and sixty-five.