ELEMENTARY MAGNETISM. 63 



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 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 changes 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, 1 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 



