called _weighing_. The
denomination and quantity of the weights used as an unit or standard for
this purpose are extremely arbitrary, and vary not only in different
kingdoms, but even in different provinces of the same kingdom, and in
different cities of the same province. This variation is of infinite
consequence to be well understood in commerce and in the arts; but, in
chemistry, it is of no moment what particular denomination of weight be
employed, provided the results of experiments be expressed in convenient
fractions of the same denomination. For this purpose, until all the
weights used in society be reduced to the same standard, it will be
sufficient for chemists in different parts to use the common pound of
their own country as the unit or standard, and to express all its
fractional parts in decimals, instead of the arbitrary divisions now in
use. By this means the chemists of all countries will be thoroughly
understood by each other, as, although the absolute weights of the
ingredients and products cannot be known, they will readily, and without
calculation, be able to determine the relative proportions of these to
each other with the utmost accuracy; so that in this way we shall be
possessed of an universal language for this part of chemistry.

With this view I have long projected to have the pound divided into
decimal fractions, and I have of late succeeded through the assistance
of Mr Fourche balance-maker at Paris, who has executed it for me with
great accuracy and judgment. I recommend to all who carry on experiments
to procure similar divisions of the pound, which they will find both
easy and simple in its application, with a very small knowledge of
decimal fractions[54].

As the usefulness and accuracy of chemistry depends entirely upon the
determination of the weights of the ingredients and products both before
and after experiments, too much precision cannot be employed in this
part of the subject; and, for this purpose, we must be provided with
good instruments. As we are often obliged, in chemical processes, to
ascertain, within a grain or less, the tare or weight of large and heavy
instruments, we must have beams made with peculiar niceness by accurate
workmen, and these must always be kept apart from the laboratory in some
place where the vapours of acids, or other corrosive liquors, cannot
have access, otherwise the steel will rust, and the accuracy of the
balance be destroyed. I have three sets