But this is only a beginning of the string of everyday incidents that are rendered curiously interesting as soon as their scientific relations and meanings become evident to you. Science is right at your elbow to raise questions and to answer them the moment you step out of bed, and your mind begins to work. As you throw open the window to see what kind of a day it is going to be, whether fair, or cloudy, or rainy, cool or warm, you draw your conclusions from the appearance of sky and air, but in doing that you are entering another field covered by another branch of science and included in our little library--meteorology, or the realm of the air--and you may be sure that the correctness of the conclusions that you draw from the aspect of the clouds and the feeling of the air will be greatly increased, not only in certainty, but also in interest, if you read what the students of this subject have learned about the laws and the mysteries of the rains, clouds, cyclones, barometric pressures, great winds and genial breezes, great storms and little storms; in short, the whole wonderful science of the atmosphere, that invisible, yet powerful kingdom of the air, which we are just beginning to annex to our world of activities without regard to what its natural occupants, the birds, think of such an invasion. Now you leave the window to begin making your morning ablutions. You turn on a faucet and take a drink, or plunge hands and face into the refreshing liquid, so cool, lively, and invigorating. But a bird or any four-footed animal may find just as keen physical enjoyment in the touch and taste of the water as you do. You, however, because you are a thinking being, possess a source of enjoyment from the touch and appearance of the water that is not open to those humbler creatures, and that source of enjoyment springs from the principles and facts of another branch of science which the mere sight of the running water may call to mind if you have caught the spirit of these books--the science of chemistry, whose early history is filled with that irresistible kind of romance that pertains to the search for Eldorado, or the strivings of the human spirit after the powers of magic; for the realm of chemistry was once a kind of semi-scientific dreamland, wherein the "alchemists" delved at the same time for the "philosopher's stone" which was to turn base metal into gold, and for the wand of the magician which would give to its possessor the boundless gratifications of a Faust. Water is no mystery to the lower animals, but it is a great mystery even yet to the highest ones--ourselves--because we have been enabled to analyze it. You cannot look at it pouring from the faucet, and sparkling into bubbles, without recalling the fact that it is composed of two invisible, silent gases, and that chemistry tells us not only how to make the water disappear by taking those gases apart, but also how to form new water by making the two gases combine. The