on the Nature of certain Bodies. 103 
owing to water in actual combination with it, like that in mu- 
riatic acid gas, and which may be essential to its elastic state ; 
but it is more probable, from the smallness of the quantity, 
and from the difference of the quantity in different cases, 
that the moisture, is merely in that state of diffusion or solu- 
tion in which it exists in gases in general, though from the 
disposition of water to be deposited in this acid gas in the 
form of an acid solution, it must be either less in quantity, or 
in a less free state, so as to require for its exhibition much 
more delicate hygrometrical tests. 
The facts advanced in this Lecture, afford no new argu- 
ments in favour of an idea to which I referred in my last 
communication to the Society, that of hydrogene being a 
common principle in all inflammable bodies ; and except in 
instances which are still under investigation, and concerning 
which no precise conclusions can as yet be drawn, the gene- 
ralization of Lavoisier happily applies to the explanation of 
all the new phenomena. 
In proportion as progress is made towards the knowledge 
of pure combustible bases, so in proportion is the number of 
metallic substances increased ; and it is probable that sulphur 
and phosphorus, could they be perfectly deprived of oxygene, 
would belong to this class of bodies. Possibly their pure ele- 
mentary matter may be procured by distillation, at a high heat, 
from metallic alloys, in which they have been acted upon 
by sodium or potassium. I hope soon to be able to try this 
experiment. 
As our inquiries at present stand, the great general division 
of natural bodies is into matter which is, or may be supposed 
to be, metallic, and oxygene ; but till the problem concerning 
