Page:Popular Science Monthly Volume 70.djvu/269

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HE basis of modern physical science is the conservation of energy. This doctrine, that the sum of the energy in our universe is constant while its modes of manifestation and transformation are indefinitely variable, has been established only within the last century, though vaguely foreshadowed many hundreds of years ago. Assuming the use of any machine for the transmission of energy, the amount of useful work done is less than the amount expended by the source because a part must be absorbed in the production and maintenance of motion in the machine itself, and in friction. With the development of heat and the radiation of this from the machine, energy that was initially available becomes transformed and ceases to be available. Such economic loss is physically a conservation.

The human brain is a machine for the transmission of energy, even though the work thus done may not be so readily measurable as that accomplished through the medium of a steam engine. The assimilation of food is the process by which energy from external sources is applied to the human machine and utilized through the medium of the brain. No physiologist has yet been able to analyze the mechanism of thought, but with the failure of the supply of carbon, hydrogen, oxygen and nitrogen, which in suitable combination constitutes food, the power of thought vanishes with the paralysis of the brain. The function of the educator is to guide and help young human beings to use to the best advantage every part of the human machine, and especially that part whose function is to originate ideas, to convey them by the use of suitable symbols, and to apply them for the benefit of the race.

The use of words for the oral conveyance of ideas, or of what are intended to be such, has always been the favorite occupation of more than a single sex. Every speaker acquires his own habits of expression that become recognized among his associates. A certain amount of what we familiarly call mental energy is put by him into the expression of an idea. Another output of such energy is expended by the hearer in the effort to take in that idea. Success is usually only partial, as every practical teacher will sorrowfully admit. Clearness of thought must precede clearness of expression, and this in turn must precede clearness of apprehension. The man's style may not be ornate, it may not be conventionally elegant, but it is good in proportion to his