ELEMENTARY MAGNETISM. 263 
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 vastnessof the field causing it, however, to be 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 selfsame 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, em- 
ployed by the chemist as a means to an end; while in 
physics proper the laws and phenomena of the agents them- 
selves, 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 enter- 
tain 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 itself. I might, of course, ring cha'nges on the 
steam-engine and the telegraph, the electrotype and the 
photograph, the medical applications of physics, and the 
various other inlets by which scientific thought filters into 
practical life. That would be easy compared with the task 
of informing you how you are to make the study of physics 
the instrument of your pupil's culture; how you are to 
possess its facts and make them living seeds which shall 
take root and grow in the mind, and not lie like dead 
lumber in the storehouse of memory. This is a task much 
heavier than the mere recounting of scientific achievements; 
and it is one which, feeling my own want of time to execute 
it aright, I might well hesitate to accept. 
But let me sink excuses, and attack the work before me. 
First and foremost, then, I would advise you to get a 
