1817.] Water is of the greatest Density. 389 
large, this renders it necessary to convert a considerable portion of 
the inner tube into an almost solid lump, in which form glass does 
not expand or contract quite so much as in an attenuated form. Or 
if, to avoid this necessity, the bulb be made comparatively small, 
the risings and depressions of the water in the neck will be propor- 
tionally minute and indistinct. 
Yet these difficulties may, I think, be so far overcome as to re- 
move any reasonable distrust of the general accuracy of the results. 
I procured two glass tubes of the requisite dimensions, equal lengths 
of which did not differ in weight so much as 5 gr. in 300; and 
I had the bulb blown of such moderate size that the inner tube did 
not require to be any where converted into a solid rod, and yet of 
such sufficient size that the expansions and contractions of the water 
were perceptible for one degree of temperature, and quite unequi- 
vocal for two degrees. I was, therefore, satisfied that the instrument 
was capable of determining, not only the existence, but very nearly 
the law, of the anomaly in question. 
The result of my trials, which I repeated oftener and more scru- 
pulously than an older experimenter would have thought at all 
necessary, is conformable to the generally received opinion. Whe- 
ther I plunged the bulb into water at 50°, and then slowly cooled it 
down to 32°, maintaining the temperature for some time stationary 
at each successive interval of two or three degrees, in order to make 
sure of its being uniformly diffused throughout both members of the 
instrument; or whether | reversed the process, by first surrounding 
the bulb with ice, and then slowly communicating heat to it; I 
found that the condensation was greatest either at 40°, or in its near 
neighbourhood, and that the rate of expansion on each side of that 
jimit was apparently the same. I even made the experiment with 
a greater degree of nicety than can be done with a graduated scale, 
by tying a fine hair round the tube, and placing it precisely opposite 
to the level of the water, after having kept it at 40° for more than 
half an hour; and I still found that any change of temperature, 
whether a rise or a fall, caused the water to ascend above the level 
of the hair. I am, therefore, almost convinced that the greatest 
density of water is at a temperature not differing from 40° by more 
than one degree; though I should not like to speak confidently on 
the subject, unless I could have the satisfaction of seeing the 
method approved, and the result verified, by some more experienced 
chemist. 
