1816.] Gaseous Bodves and the Weight of their Atoms. 113 
In this table it will be also observed that the new determinations 
of Gay-Lussac respecting the prussic acid, &c. are inserted, to show 
that they correspond with, and further corroborate, the views which 
have been brought forward in the essay above referred to. 
There is an advantage in considering the volume of hydrogen 
equal to the atom, as in this case the specific gravities of most, or 
perhaps all, elementary substances (hydrogen being 1) will either 
exactly coincide with, or be some multiple of, the weights of their 
atoms; whereas if we make the volume of oxygen unity, the 
weights of the atoms of most elementary substances, except oxygen, 
will be double that of their specific gravities with respect to hydrogen. 
The assumption of the volume of hydrogen being equal to the atom 
will also enable us to find more readily the specific gravities of 
bodies in their gaseous state (either with respect to hydrogen or 
atmospheric air), by means of Dr. Wollaston’s logometric scale. 
If the views we have ventured to advance be correct, we may 
almost consider the zparn vay of the ancients to be realised in 
hydrogen; an opinion, by the by, not altogether new. If we 
actually consider this to be the case, and further consider the spe-' 
cific gravities of bodies in their gaseous state to represent the 
number of volumes condensed into one; or, in other words, the 
number of the absolute weight of a single volume of the first matter 
(xparn vay) which they contain, which is extremely probable, 
multiples in weight must always indicate multiples in volume, and 
viee versé; and the specific gravities, or absolute weights of all 
bodies in a gaseous state, must-be multiples of the specific gravity 
or absolute weight of the first matter (apéty Ay), because all 
bodies in a gaseous state which unite with one another unite with 
reference to their volume. 
Articie VIII. 
On the Marquis de Chabanne’s Method of Ventilating Houses. 
By Mr. Arnot, Surgeon. 
(To Dr. Thomson.) 
DEAR SIR, 
Some days ago I went to examine a new plan of warming and 
ventilating houses exemplified at No. 1, Russel-place, Fitzroy- 
square, in the house of the inventor. My first impression on en- 
tering it, and beginning to consider the subject, was a feeling of 
surprise at its never having occurred to me before to inquire atten- 
tively whether objects of such importance are or are not completely 
fulfilled in our present habitations: but my surprise was much in- 
creased when a slight review of the subject convinced me that it 
must have been hitherto almost totally neglected by men of science. 
