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minute of mean time, as correct. On this presumption, I shall 
proceed to the examination of weight. 
(§.5.) From the opinion of different skilful persons, with 
whom I have conferred, as well as from the result of my own 
considerations, I am inclined to believe there is hardly any body 
in nature, with which we are familiarly acquainted, that is of so 
simple and homogeneous a quality as pure distilled water, or so 
fit for the purposes of this inquiry ; and I have concluded, that 
if the weight of any quantity of water, whose bulk had been 
previously measured by the abovementioned scale, could be 
obtained, under a known pressure* and temperature of the at- 
mosphere, we should be in possession of a general standard of 
weight. 
(§.6.) With this view, I directed Mr. Troughton to make, 
in addition to the very sensible hydrostatic balance before men- 
tioned, a solid cube of brass, whose sides were 5 inches ; and 
also a cylinder of the same metal, 4 inches in diameter, and 6 
high. From St. Thomas's hospital, by the favour of Dr. For- 
dyce, I procured 3 gallons of distilled water. With these I 
made the following observations ; but, before I relate the ex- 
■ ■; periments, I will describe the apparatus. 
Mr. Whitehurst's machine for measuring the pendulum 
has been sufficiently explained in his pamphlet mentioned 
above; my divided scale, which was a new instrument, was 
as follows. 
• I d© not here mean to infer any opinion respecting the compressibility of water ; 
but only to say, that where water, or any thing else, is weighed in air, the density of 
that medium, as shewn by the barometer and thermometer, must be known, in order 
to make allowances fo-r it, if necessary. 
