t actually to touch his work.
He may otherwise be a distributor of knowledge, but not a creator, and
he fails to attain that vitality of thought, and correctness of
judgment, which direct and habitual contact with natural truth can
alone impart.

One large department of the system of Nature which forms the chief
subject of my own studies, and to which it is my duty to call your
attention this evening, is that of physics, or natural philosophy.
This term is large enough to cover the study of Nature generally, but
it is usually restricted to a department which, perhaps, lies closer
to our perceptions than any other. It deals with the phenomena and
laws of light and heat--with the phenomena and laws of magnetism and
electricity--with those of sound--with the pressures and motions of
liquids and gases, whether at rest or in a state of translation or of
undulation. The science of mechanics is a portion of natural
philosophy, though at present so large as to need the exclusive
attention of him who would cultivate it profoundly. Astronomy is the
application of physics to the motions of the heavenly bodies, the
vastness of the field causing it, however, to bed regarded as a
department in itself. In chemistry physical agents play important
parts. By heat and light we cause atoms and molecules to unite or to
fall asunder. Electricity exerts a similar power. Through their
ability to separate nutritive compounds into their constituents, the
solar beams build up the whole vegetable world, and by it the animal
world. The touch of the self-same beams causes hydrogen and chlorine
to; unite with sudden explosion, and to form by their combination a
powerful acid. Thus physics and chemistry intermingle. Physical
agents are, however, employed by the chemist as a means to an end;
while in physics proper the laws and phenomena of the agents
themselves, both qualitative and quantitative, are the primary objects
of attention.

My duty here to-night is to spend an hour in telling how this subject
is to be studied, and how a knowledge of it is to be imparted to
others. From the domain of physics, which would be unmanageable as a
whole, I select as a sample the subject of magnetism. I might readily
entertain you on the present occasion with an account of what natural
philosophy has accomplished. I might point to those applications of
science of which we hear so much in the newspapers, and which are so
often mistaken for science it