Thoroughly convinced of these truths, I have imposed upon myself, as a
law, never to advance but from what is known to what is unknown; never
to form any conclusion which is not an immediate consequence necessarily
flowing from observation and experiment; and always to arrange the
facts, and the conclusions which are drawn from them, in such an order
as shall render it most easy for beginners in the study of chemistry
thoroughly to understand them. Hence I have been obliged to depart from
the usual order of courses of lectures and of treatises upon chemistry,
which always assume the first principles of the science, as known, when
the pupil or the reader should never be supposed to know them till they
have been explained in subsequent lessons. In almost every instance,
these begin by treating of the elements of matter, and by explaining the
table of affinities, without considering, that, in so doing, they must
bring the principal phenomena of chemistry into view at the very outset:
They make use of terms which have not been defined, and suppose the
science to be understood by the very persons they are only beginning to
teach. It ought likewise to be considered, that very little of chemistry
can be learned in a first course, which is hardly sufficient to make the
language of the science familiar to the ears, or the apparatus familiar
to the eyes. It is almost impossible to become a chemist in less than
three or four years of constant application.
These inconveniencies are occasioned not so much by the nature of the
subject, as by the method of teaching it; and, to avoid them, I was
chiefly induced to adopt a new arrangement of chemistry, which appeared
to me more consonant to the order of Nature. I acknowledge, however,
that in thus endeavouring to avoid difficulties of one kind, I have
found myself involved in others of a different species, some of which I
have not been able to remove; but I am persuaded, that such as remain do
not arise from the nature of the order I have adopted, but are rather
consequences of the imperfection under which chemistry still labours.
This science still has many chasms, which interrupt the series of facts,
and often render it extremely difficult to reconcile them with each
other: It has not, like the elements of geometry, the advantage of being
a complete science, the parts of which are all closely connected
together: Its actual progress, however, is so rapid, and the facts,
under the modern doctrine, have assumed so happy an arrangement, that we
have ground to hope, even in our own times, to see it approach near to
the highest state of perfection of which it is susceptible.
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