Classification of simple Bodies. 439 
Hitherto chemists have confined themselves to ranging simple 
bodies according to the degree of their affinity for oxygen, and 
the natifre of the combinations which they form with it. They 
ought naturally to have adopted this kind of classification, when 
they thought that the properties which characterized the oxygen 
belonged to it in a manner so exclusive that no other body could 
be associated with it. But nowadays that new facts, and a 
more accurate interpretation of the facts already known, have 
rectified whatever was too absolute in the theory established by 
the celebrated Lavoisier; and now that other substances have 
presented similar properties ; it appears to me that we must of 
necessity banish from chemistry the artificial classifications, and 
begin by assigning to each simple body the place which it ought 
to occupy in the natural order, by comparing it successively with 
all the rest, and uniting it with those which resemble it by a 
greater number of common characters, and particularly by the 
importance of those characters. The first advantage whieh will 
result from the employment of such a method, will be to give us 
4 more exact and more complete knowledge of all the properties 
of simple bodies; and frequently to refer to general laws a mul- 
titude of isolated facts. Another advantage will arise from this, 
namely, that after having ascertained among those which we 
shall have thus united, analogies so multiplied that we cannot 
refuse to regard them as connected very closely in the natural or- 
der, we shall be led to try upon some, experiments similar to those 
which have been attempted with success on others. A classifi- 
eation, which should have induced every person from the very 
origin of modern chemistry to consider all the salifiable bases as 
belonging to one and the same class of bodies, would have taught 
chemists to place potash and soda in contuct with iron at a high 
temperature, and potash and soda would have been discovered 
twenty years sooner. When it was ascertained that chlore was 
a simple body, it was at first compared to oxygen ; and it was 
only when M. Gay-Lussac remarked its analogies with sulphur, 
that he was led to a discovery, the consequences of which upon 
the ulterior progress of chemistry can only as yet be guessed at, 
viz. that of the chlorie and iodic acids, and of the perfect ana~ 
logy of the chlorates and iodates with the nitrates, A second 
approximation followed almost instantly by another diseovery 
to which it naturally led, that of cyanogene, and of the true na- 
ture of the hydrocyanic acid. Finally, these very analogies 
doubtless guided M. Dulong in the work which he communi- 
eated to the Institute on the 7th of November 1815, in which 
we see that the oxalic acid is composed of carbonic acid gas and 
hydrogen gas combined in the bog of two to one in volume ; that 
e4 this 
