“Terrestrial life depends upon its rays. I say depends upon them—life is a form of solar energy. It is the sun which maintains water in a liquid state, and the atmosphere in a gaseous one; without it all would be solid and lifeless; it is the sun which draws water from the sea, the lakes, the rivers, the moist soil; which forms the clouds and sets the air in motion; which produces rain and controls the fruitful circulation of the water; thanks to the solar light and heat, the plants assimilate the carbon contained in the carbonic acid of the atmosphere, and in separating the oxygen from the carbon and appropriating the latter the plant performs a great work; to this conversion of solar into vital energy, as well as to the shade of the thick-leaved trees, is due the freshness of the forests; the wood which blazes on our hearthstones does but render up to us its store of solar heat, and when we consume gas or coal today, we are only setting free the rays imprisoned millions of years ago in the forests of the primary age. Electricity itself is but a form of energy whose original source is the sun. It is, then, the sun which murmurs in the brook, which whispers in the wind, which moans in the tempest, which blossoms in the rose, which trills in the throat of the nightingale, which gleams in the lightning, which thunders in the storm, which sings or wails in the vast symphony of nature. “Thus the solar heat is changed into air or water currents, into the expansive force of gases and vapors, into electricity, into woods, flowers, fruits and muscular energy. So long as this brilliant star supplies us with sufficient heat the continuance of the world and of life is assured.