72 Sir H. Davy's Account oj some new Experiments 
this principle, or of other principles, should not be assumed 
where they could not be detected. 
In all cases, in which bodies support combustion or form 
acids, oxygen has been supposed by the greater number of 
modern chemists to be present ; but as there are many dis- 
tinct species of inflammable bodies, so there may be many 
distinct species of matter which combine with them with so 
much energy, as to produce heat and light ; and various bodies 
appear capable of forming acids; thus hydrogen enters into 
the composition of nearly as many acids as oxygen, and three 
bodies, namely, sulphuretted hydrogen, muriatic acid, and 
fluoric acid which contain hydrogen, are not known to contain 
oxygen. The existence of oxygen in the atmosphere, and its 
action in the economy of nature, and in the processes of the 
arts, have necessarily caused it to occupy a great portion of 
the attention of chemists, and, being of such importance, and 
in constant operation, it is not extraordinary, that a greater 
number of phenomena should be attributed to it, than it really 
produces. 
In the views that I have ventured to develope, neither oxy- 
gen, chlorine, or fluorine, are asserted to be elements ; it is 
only asserted, that, as yet, they have not been decomposed. 
As the investigation of nature proceeds, it is not improbable, 
that other more subtile bodies belonging to this class will be 
discovered, and perhaps some of the characteristic differences 
of those substances, which apparently give the same products 
by analysis, may depend upon this circumstance. 
The conjecture appears worth hazarding, whether the car- 
bonaceous matter in the diamond may not be united to an 
extremely light and subtile principle of this kind, which has 
