476 Proceedings of Philosophical Societies. [JUNE, 
retain their old form. The one which we offer at present to the 
public will unite without interruption to the preceding ones. 
Let us hope that Peace, the communications which it opens, and 
the emulation which it excites, will contribute to render the con- 
tents of our analyses more and more interesting. 
PHYSICS AND CHEMISTRY. 
It is well known that the different bodies, and particularly the 
different liquids, are dilated by heat in very different proportions. 
M..Gay-Lussac has endeavoured to discover some law which 
should point out the rule of these proportions. For this purpose, 
instead of comparing the dilatations of different liquids above or 
below a uniform temperature for all, he set out from a point 
variable in point of temperature, but uniform as far as regards the 
cohesion of the molecules; namely, from the point at which each 
liquid boils under a given pressure ; and among those which he exa- 
mined he found two which dilate equally from that point. These 
are alcohol and sulphuret of carbon; which boil, the former at 
173°14°, the latter at 115:9°. The other liquids did not present in 
this respect the same resemblance. On inquiry into the other ana- 
logies of the two liquids in question, M. Gay-Lussac ascertained 
that they resemble each other likewise in this respect, that the same 
volume of each at its boiling point gives under the same pressure 
the same volume of vapour; or, in other terms, that the densities 
of their vapours are to each other as those of the liquids at their 
respective boiling temperatures. 
M. Gay-Lussac promises to prosecute his researches, and to pre- 
sent shortly a more complete set of experiments on the dilatation of 
liquids and their capacity of heat, compared with the capacities of 
their vapours, 
Among the delicate questions with which chemistry is at present 
- occupied, we ought to place that which regards the proportions ac- 
cording to which the elements are capable of uniting to form the 
different kinds of compounds. It has been lately observed that 
there are certain limits which nature affects, expressed by terms 
generally simple; and, according to the researches of Gay-Lussac, 
this is the case particularly with the combinations of the gases when 
we regard not their absolute weight, but their volume under an 
equal pressure. 
These researches are liable to great difficulties, because it is not 
always possible to obtain the combinations isolated ; and when we 
wish to separate them from the salts of which they constitute a part, 
they are decomposed or altered by the other principles of these salts, 
or by the water which almost always enters into them. 
In this way we may explain the striking differences in the results 
of Davy, Dalton, and Gay-Lussac, respecting the combinations of 
azote and oxygen. 
From the experiments presented during this year to the Academy 
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