FREE AND PERFECTLY ELASTIC MOLECULES IN A STATE OF MOTION. 05 
will be remarked that in the act of rising into vapour it is decomposed, and what is 
one volume in the case of oxalic ether vapour is two volumes in the case of nitrous 
ether. Several other examples of this kind will be found. I have already referred 
to such facts as being favourable to the hypothesis of media which attributes a 
mechanical origin to the law of volumes, and have likewise referred to the remarkable 
circumstance that compounds which thus disunite in the act of vaporization neverthe¬ 
less obey the general law of vapours (see Note B). As it seems, from the nature of 
the function that expresses this law, that a mechanical origin may be found for it 
also, the investigation of the subject might, perhaps, be made easier if the chart lines 
of vapour were determined for mixtures of pure alcohol and water in all proportions, 
and also for mixtures of alcohol and ether. 
We should then, perhaps, discover the law of variation of the two constants G and 
H of the chart line, and this might provide us with a new condition or effect of the 
primary cause pointing to its origin from a new ground. 
The two last columns contain the constants G and H, referred to in Note B. ; 
where there are three places of decimals the numbers are nearly exact, when two only 
they are to be considered as approximate. 
Column No. 1 contains the temperature on Fahrenheit scale at which the vapour 
in contact with its generating solid or liquid equilibrates a pressure of 30 inches of 
mercury. 
Column No. 2 contains the specific gravity of the body in its usual liquid or solid 
form. 
Column No. 3 contains, as before mentioned, the specific gravity of the body in its 
gaseous form in terms of hydrogen unity. It expresses the weight of a molecule of 
the hypothetical medium that answers to the gas in its physical relations. 
Column No. 4 contains the inverse of the specific heat of the body in its usual 
liquid, solid, or gaseous form. The numbers are found by dividing the constant 3'2 
by the specific heat. This constant is the product of the specific heat of air by its 
specific gravity in terms of hydrogen unity, and to the same product of all gases that 
conform to the law of equal volumes having the same specific heat. It is likewise 
the product of the specific heat of mercury in its liquid form by the specific gravity of 
its vapour (Note E). In other elementary bodies this product is-a simple multiple of 
the same constant. In compounds the same product is also in most cases a simple 
multiple of the same constant. On the vis viva theory of heat the numbers in this 
column probably show the mean weight of the component parts of the gaseous 
molecule that have an independent motion when the body is in the liquid or solid 
form. Thus, No. 33, arsenious acid : the specific gravity of the vapour is 200 times 
that of hydrogen ; but its specific heat in the solid form is 8 times what it is in the 
state of vapour, if in this form it obeyed the law of the specific heat of gases. Hence 
25 is the number opposite in this column, which, since it goes 8 times in 200, shows 
that the molecule consists of about 8 parts, each of which has an independent 
MDCCCXCII.-A. K 
