Warbled rounds of music broke.
Winds that held their breath to listen
Swept adown the vine-clad rooms,
Crowned the little prima-donna
With soft-shaken elder blooms.
—Mrs. A. S. Hardy.
SPRINGS, GEYSERS AND ARTESIAN WELLS.
If the earth were transparent as the atmosphere we should see many things of wonderful interest and beauty beneath its surface. If we could see the mineral gems that lie beneath the earth’s surface they would rival in beauty the jeweled firmament above us. We should also see rivers and rivulets of crystal clearness and lakes of broad expanse. I can almost hear my young readers saying, “I wish we could look beneath the surface of the earth and see the wonderful and beautiful things it contains, just as we look up to the stars, or out of the window upon a landscape.” But let me remind them that nature has been very generous in furnishing rare and wonderful things for them to study and admire to which they can have easy access almost every day. The longest life is too short to study and admire more than a few of the things we may see upon the surface of the earth. Nature has opened a few doors so that we may walk in, study and admire the work she is carrying on in the darkness where the light of the sun never penetrates. Nature makes a free use of sunlight to perfect her most beautiful work upon the surface of the earth, but her most delicate and beautiful work beneath the surface of the earth is wrought by other agencies. Caves have been entered and explored by natural openings, and springs and rivers gush out at the surface of the earth, telling us plainly that they are fed by subterranean fountains and lakes.
Following the order of our topic, let us see what we can find out about underground streams and lakes, and why we know they exist when we seldom see them. We know that large rivers after flowing miles upon the surface of the earth suddenly drop into subterranean channels and reappear after running miles underground. Springs which are always flowing must be constantly fed from some source beneath the surface of the earth. In boring wells the augers, after going down to various depths, suddenly drop several feet, showing that they have reached a cavity in the earth or a fountain of water; if the water gushes up it is evident a fountain has been struck.
Where does the water come from to fill the underground lakes and reservoirs and keep the rivers constantly flowing? Geologists tell us that all the land surface of the earth was for vast ages under water; that the great oceans that now roll between the continents once covered them entirely, but after long ages mighty internal forces of the earth raised them above the ocean’s level. For a long time after the hills and mountains were raised above the surface of the ocean, where the valleys and prairies now are there were lakes and inland seas. The water in these lakes and seas did not all evaporate or find its way to the ocean by the rivers that flowed from them. Deep down into the earth much of it found its way, along the fissures and porous strata, until it reached some impervious stratum, as clay or granite. But as this first underground supply would in time become exhausted, by flowing into the ocean through the rivers they fed, nature has made further provision for keeping up the supply. Everywhere upon the surface of the earth where there is water or moisture evaporation is going on. The sun raises enormous quantities of water in the form of vapor, which forms clouds and descends in rain. A part of this water is soon restored to the sea by the rivers, but by far the largest portion penetrates the earth’s surface, as water would penetrate cloth or a sponge when poured upon it. Rain penetrating the earth goes down until it comes to some substance that it cannot penetrate. Then, in trying to find its level, it will distribute itself just as it does upon the surface of the earth. It will find its way into cavities, large and small, or following some underground channel or stratum, it may burst forth a clear and sparkling spring, or it may flow on a rivulet, or river, and perhaps enter into a great subterranean lake. The underground fountain or lake that keeps an artesian well spouting from year to year may be fed by a stream or lake in the heart of some distant mountain. Some artesian wells cease to flow after a while, showing that the fountain that supplies them is at least partially exhausted. We do not know to what depth water penetrates the earth. Artesian wells have been bored in recent years to the depth of four thousand feet. The temperature of springs and artesian wells is regulated by the temperature of the strata through which the water percolates. The geysers of Iceland send up enormous jets of hot water in the midst of Arctic cold.