LIGHT.

CHAPTER I.

INTRODUCTION.

ALL about us are men busy with their various trades and professions: sailing ships, digging in mines, making all manner of useful tools and machinery, planting seeds and reaping harvests, and doing many other works and labors according to certain fixed rules that they found printed in books, or that they learned of others, or that they discovered for themselves. Each one has to do with the physical phenomena around him. The more he knows about these phenomenathe more he knows about things, their relation to each other, and their action one upon another-the better he can work. A knowledge of the phenomena of Nature is the most important knowledge one can have who wishes to succeed in life. More than this,

the observation of facts in Nature gives readiness of perception, and study and reading upon the causes of these facts stimulate the mind to healthful and pleasurable action.

The laws that govern the physical phenomena about us were not told to us by ancient gods, or divinely-instructed men. They were discovered by experiment or observation. Men asked questions of Nature; they watched her phenomena, till they felt sure they saw a reason for their action. Sometimes they did not understand all that happened, and made strange guesses at the laws that governed the happenings. Other men repeated the experiments and got new answers; and thus, in time, the truth about things became known. Many of these facts in Nature, and the laws that govern their action, are now known of all men. Others are still obscure, or dimly known, and are being investigated every day in the hope that they may be better understood.

The farmer, the sailor, the mechanic, and artisan, most familiar with these facts and laws of Nature, is, other things being equal, the most likely to be successful in his work. You hope to have a share in the world's work, and you wish to study Nature and her phenomena. You can read about these things in books. A better way is to make experiments-to ask