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XXV. On the Variation of the Temperature- of boiling 
Water. By Sir George Shuck burgh, Baronet , F. R. 
and A. S. and Member of the Academy of Sciences and 
Belles Lettres at Lyon. 
Read March 1 1, 1779. 
* I "'HE heat of boiling water having for fome years been 
ufed as one of the terms for graduating the fcale 
of thermometers ; together with the particular attention 
the Society has lately given {vide the Report of the Com- 
mittee, Phil. Tranf.vol. lxvii.) to this branch of inquiry, 
and I may add the lingular fuccefs with which this age 
and nation has introduced a mathematical precilion, hi- 
therto unheard of, into the conftru&ion of philofophical 
inftruments, will render it unneceffary for me to fay 
more in refpecSt of the following experiments, than lim- 
ply to lay them before the Royal Society. 
That the heat of boiling water was variable, accord- 
ing to the preffure of the atmofphere, feems to have 
been known to Fahrenheit as early as the year 1 7 24/^. 
(a) Vide Phil. Tranf. N° 385. wherein is propofed a curious projeft of de- 
termining the weight of the atmofphere by means of a thermometer alone, un- 
der the title of u Barometri novi defcriptio.” 
A few 
