The Text-book now offered to the public has been prepared to meet the
existing want of a practical "handy book" for the Assayer.

To mining men the word "assaying" conveys a sufficiently clear meaning,
but it is difficult to define. Some writers limit it to the
determination of silver and gold, and others imagine that it has only to
do with "furnace-work." These limitations are not recognised in
practice. In fact, assaying is becoming wider in its scope, and the
distinction between "assayers" and "analysts" will in time be difficult
to detect. We have endeavoured rather to give what will be of use to the
assayer than to cover the ground within the limits of a faulty
definition.

At first our intention was to supply a description of those substances
only which have a commercial value, but on consideration we have added
short accounts of the rarer elements, since they are frequently met
with, and occasionally affect the accuracy of an assay.

Under the more important methods we have given the results of a series
of experiments showing the effect of varying conditions on the accuracy
of the process. Such experiments are often made by assayers, but seldom
recorded. Statements like those generally made--that "this or that
substance interferes"--are insufficient. It is necessary to know under
what conditions and to what extent.

Students learning any particular process cannot do better than repeat
such a series of experiments. By this means they will, at the same time,
acquire the skill necessary for performing an assay and a confidence in