We all know the consequences of wanton extravagance. We know it spells bankruptcy and ruin. The expenditure of heat by the sun is the most magnificent extravagance of which human knowledge gives us any conception. How have the consequences of such awful prodigality been hitherto averted? How is it that the sun is still able to draw on its heat reserves from second to second, from century to century, from eon to eon, ever squandering two thousand million times as much heat as that which genially warms our temperate regions, as that which draws forth the exuberant vegetation of the tropics, or which rages in the Desert of Sahara? This is indeed a great problem.
It was Helmholtz who discovered that the continual maintenance of the sun's temperature is due to the fact that the sun is neither solid nor liquid, but is to a great extent gaseous. His theory of the subject has gained universal acceptance. Those who have taken the trouble to become acquainted with it are compelled to admit that the doctrine set forth by this great philosopher embodies a profound truth.
A TYPICAL SUN-SPOT
Even the great sun cannot escape the application of a certain law which affects every terrestrial object, and whose province is wide as the universe itself. Nature has not one law for the rich and another for the poor. The sun is shedding forth heat, and therefore, affirms this law, the sun must be shrinking in size. We have learned the rate at which this contraction proceeds; for among the many triumphs which mathematicians have accomplished must be reckoned that of having put a pair of callipers on the sun so as to measure its diameter. We thus find that the width of the great luminary is ten inches smaller to-day than it was yesterday. Year in and year out the glorious orb of heaven is steadily diminishing at the same rate. For hundreds of years, aye, for hundreds of thousands of years, this incessant shrinking has gone on at about the same rate as it goes on at present. For hundreds of years, aye, for hundreds of thousands of years, the shrinking still will go on. As a sponge exudes moisture by continuous squeezing, so the sun pours forth heat by continuous shrinking. So long as the sun remains practically gaseous, so long will the great luminary continue to shrink, and thus continue its gracious beneficence. Hence it is that for incalculable ages yet to come the sun will pour forth its unspeakable benefits; and thence it is that, for a period compared with which the time of man upon this earth is but a day, summer and winter, heat and cold, seedtime and harvest, in their due succession, will never be wanting to this earth.