What should we think of the prudence of a man who, having been endowed with a splendid fortune of not less than twenty million dollars, spent one cent of that vast sum usefully and dissipated every other cent and every other dollar of his gigantic wealth in mere aimless extravagance? This would, however, appear to be the way in which the sun manages its affairs, if we are to suppose that all the solar heat is wasted save that minute fraction which is received by the earth. Out of every twenty million dollars' worth of heat issuing from the glorious orb of day, we on this earth barely secure the value of one single cent; and all but that insignificant trifle seems to be utterly squandered. We may say it certainly is squandered so far as humanity is concerned. No doubt there are certain other planets besides the earth, and they will receive quantities of heat to the extent of a few cents more. It must, however, be said that the stupendous volume of solar radiation passes off substantially untaxed into space, and what may actually there become of it science is unable to tell. And now for the great question as to how the supply of heat is sustained so as to permit the orb of day to continue in its career of such unparalleled prodigality. Every child knows that the fire on the domestic hearth will go out unless the necessary supplies of wood or coal can be duly provided. The workman knows that the devouring blast furnace requires to be incessantly stoked with fresh fuel. How, then, comes it that a furnace so much more stupendous than any terrestrial furnace can continue to pour forth in perennial abundance its amazing stores of heat without being nourished by continual supplies of some kind? Professor Langley, who has done so much to extend our knowledge of the great orb of heaven, has suggested a method of illustrating the quantity of fuel which would be required, if indeed it were by successive additions of fuel that the sun's heat had to be sustained. Suppose that all the coal seams which underlie America were made to yield up their stores. Suppose that all the coal fields of England and Scotland, Australia, China, and elsewhere were compelled to contribute every combustible particle they contained. Suppose, in fact, that we extracted from this earth every ton of coal it possesses, in every island and in every continent. Suppose that this vast store of fuel, which is adequate to supply the wants of this earth for centuries, were to be accumulated in one stupendous pile. Suppose that an army of stokers, arrayed in numbers which we need not now pause to calculate, were employed to throw this coal into the great solar furnace. How long, think you, would so gigantic a mass of fuel maintain the sun's expenditure at its present rate? I am but uttering a deliberate scientific fact when I say that a conflagration which destroyed every particle of coal contained in this earth would not generate so much