BY PROF. J. T. EDWARDS, D.D.
Director of the Chautauqua School of Experimental Science.
WATER.—PHYSICAL PROPERTIES.
A glance at the map of our earth at once reveals the preponderance of water. Three-fourths of its surface is covered by the ocean, and if we divide the globe into northeastern and southwestern halves, one of the hemispheres will consist almost entirely of water. Yet there was a time when the ocean was still more extensive and covered islands and continents; even the loftiest mountain peaks were beneath the sea. We shall presently see how important an agency water became in moulding the earth and making it habitable for man. The lakes and rivers also constitute no small part of many lands, and even in the air, invisible streams are ever flowing, for “all the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come thither they return again.” The summer’s heat is the power, and the air its instrument, by which vapors, fogs, clouds and rain are lifted and borne back to the mountains and again scattered over the plains.
WATER SEEKING ITS LEVEL.
WATER AS AN ARCHITECT—WORLD-BUILDING.
In the divine hand water has been used as the material with which to shape the earth, even as a workman employs his files, emery and diamond dust to shape the objects upon which he labors. At first the earth was characterized by one dead level—a wide, desolate, fire-scarred plain; then the mountains were upheaved, the depths were broken up, and, no longer resting in their quiet beds, everywhere rolled down the slopes, and by mere attrition, wore away the firm rocks and bore the material into the plains below; all valleys have thus been made. Some are still in process of formation. Far out in the Gulf of Mexico, and in the Indian Ocean, the Mississippi and the Ganges are pouring their sediment and building future continents. Sometimes, where the volume of water was great, or the mountains steep, mighty gorges were carved out, like the river-bed below Niagara, the tremendous cuts of the Congo, or the awful cañons of the Colorado, some of which are five thousand feet in depth. Ceaseless waves beat upon the shore, powdered the rocks, and made the soft beaches; tides ebbed and flowed, and slowly wrought their changes. In addition to the wearing action of the water, which arises from the smoothness of its molecules, and the slight cohesion of its particles, thereby causing ceaseless motion, it possesses a wonderful solvent power. Solution arises from the fact that the adhesion between a liquid and a solid is greater than the cohesion between the molecules of the solid; whenever this is the case the latter will be dissolved. If water is heated, this action will be intensified; such was its condition in the early geologic ages, and this explains the extraordinary rapidity with which rocks were then dissolved. Beautiful grottoes were formed like that of Antiparos, vast caverns, such as those along the coasts of Scotland, the Mammoth Cave of Kentucky, and the Wyandotte of Indiana. It is a curious paradox which appears in this story of world-building that the New World was really the oldest in process of formation, and that the tallest mountains were the latest upheaved.
