444 Hesearches respecting the Laws of the (JUNE, 
philosophers have shown long-ago that when a liquid is enclosed in 
a close vessel it is capable of supporting without boiling a much 
higher temperature than the point at which it boils in the open air; 
and the theory of Mr. Dalton on the formation of vapours gives a 
satisfactory reason for this fact. Accordingly alcohol thermometers 
have been long made capable of bearing the heat of boiling water. 
We sce from our formulas that the dilatation of alcohol in these 
extreme limits, instead of being irregular, continues conformable 
to itself, and follows the same law at the temperature of boiling 
water as at 10° Reaumur below zero; only, as this dilatation is not 
proportional to that of mercury, it is easy to conceive that its abso- 
lute value is not the same in different parts of the thermometrical 
scale for the same number of degrees of the thermometer. ‘This is 
strikingly confirmed by an observation of Mr, Dalton himself on the . 
absolute dilatation of alcohol in a glass vessel from — 17°78° R., to 
+ 62°22°, which includes an interval of 80°. The dilatation in 
this interval ought not to be the same as from 0 to 80. In fact, by 
calculating from our formula, we find 
From 0 to — 17°78 the true dilatation .......... —0°0209325 
From 0 to + 62°22 the true dilatation ....... ... +0°0919566 
Difference of total dilatation from — 17°78 to 
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Substracting the dilatation of the glass — 80K.... 0°0026272 
We have the apparent dilatation..........2+.... O°1102619 
The value found by'Dalton is ¢ 20.0. 22. ce es) OTR 
It is exactly the same with ours in the number of decimals that 
he bas retained. ‘This conformation of our formulas is so much the 
stronger, as no determination below zero entered into their con- 
struction, though I afterwards compared them with the experiments 
of Deluc made at — 10° R., in order to see if they would hold 
good at that point. 
Mr. Dalton likewise gives us a confirmation in his work of the 
value which I have ascribed to the absolute dilatation of water be- 
tween the temperatures of 0 and 80° R.; for he states it from ex- 
periment at 0°0466, precisely as I had deduced it from the thermo- 
metrical observations of Deluc, combined with a single determina- 
tion of the weight of water by Blagden and Gilpin at the tempera- 
ture of 30°22°. 
Saline solutions and oils having very different dilatations from 
water, cannot agree with the hypothesis of Dalton. Accordingly, 
he excludes them from his hypothesis, which he confines to what he 
calls the simple liquids, such as mercury.and water, which are the 
ones that agree with it best, though it is inconsistent with the phy- 
sical properties of mercury. Yet we have seen that experiments 
made upon the most complex liquids, the oils, saline solutions, mix- 
tures of water and alcohol, may be all represented by our formulas, 
and lose in them their apparent irregularity, Besides, as these for- 
