372 Analyses of Books. [May, 
which is not the case with those substances that contain oxygen 
as a constituent. , 
When we consider the metals with regard to their combustibi- 
lity, we get a new example of a similar gradation of a property 
in the same series. From the most combustible metal to gold, 
the metals form a series of gradations, the terms of which are 
sufficiently known. When we come to gold, we may continue 
the series by platinum, which is still less combustible than gold. 
Then come osmium and iridium, in which the combustibility is 
so weak that acids are incapable of attacking them; though the 
alkalies favour. their oxidation in a state of incandescence. 
Having thus come to a point in the series where the combusti- 
bility in some measure disappears, we may continue it to the 
most absolute incombustility. A body is perfectly incombustible 
when its presence is necessary for combustion going on.* 
Among the unburnt bodies which we know, oxygen is the only 
one that we can consider as incombustible.+ Tf it should be 
discovered hereafter that oxygen may be burned by means of 
another principle, it will not be the less true that the body whose 
properties are most opposite to those of combustible bodies is 
the only really incombustible substance. Oxygen, therefore, 
must obviously terminate the series of undecomposed bodies as 
being perfectly incombustible, and thus at the greatest possible 
distance from the body with which the series commenced, 
Thus Professor GErsted makes the same division of simple 
bodies that I have done in my System of Chemistry ; namely, 
into combustibles and supporters; which last bodies he calls 
bodies possessing la proprieté comburente. I think the term 
which I have been in the habit of using is better suited to our 
lapguage than any translation of his appellation which I could | 
have adopted. It is gratifying to observe such a subdivision 
advanced by a gentleman that im all likelihood was unacquainted 
with my arrangement ; because it adds greatly to the probability 
that the arrangement itself is founded in the nature of things. 
CErsted’s series of simple substances then begins with the most 
perfect combustible, and terminates with the mest perfect 
supporter. 
Some bodies are very combustible in certain circumstances, 
while they are very little so in others. We must, therefore, 
establish a comparison between these bodies while they are in 
the same circumstances. Carbon is capable, for example, of 
reducing the greater number of the metals, and yet it cannot be 
considered as a very combustible body; for at the ordinary 
* Todine was unknown when this book was published ; and though CErsted was: 
aware of Davy’s hypothesis respecting chlorine, he at that time leaned to the old 
doctrine, for reasons which he assigns; but which do not seem of much weight.—T. 
tT My readers will understand-what Prof, Girsted means when I mention that 
his perfectly incombustible bodies are those which I call supporters of combustion, —T, 
