thought best to intersperse throughout the book, placing each
where it seemed to be especially needed; in this way, it is hoped
that the tedium which pupils find in studying consecutively many
chapters of theories will be avoided, and that the arrangement
will give an occasional change from the discussion of facts and
experiments to that of principles. In these chapters additional
questions should be given, and the pupil should be particularly
encouraged to make new problems of his own, and to solve theta.

It is needless to say that this treatise is primarily designed to
be used in connection with a laboratory. Like all other text-
books on the subject, it can be studied without such an
accessory; but the author attaches very little value to the study
of Chemistry without experimental work. The required apparatus
and chemicals involve but little expense, and the directions for
experimentation are the result of several years' experience with
classes as large as are to be found in the laboratory of any
school or college in the country.

During the present year the author personally supervises the work
of more than 180 different pupils in chemistry. This enables him
not only to assure himself that the experiments of the book are
practical, but that the directions for performing them are ample.
It is found advisable to perform most of the experiments, with
full explanation, in presence of the class, before requiring the
pupils either to do the work or to recite the lesson. In the
laboratory each pupil has a locker under his table, furnished
with apparatus, as specified in the Appendix. Each has also the
author's "Laboratory Manual," which contains on every left-hand
page full directions for an experiment, with observations to be