Now when you reflect upon these various changes you will see that through the agency of this same internal heat land is preserved upon the face of the earth. If rain and frost, rivers, glaciers, and the sea were to go on wearing down the surface of the land continually, without any counterbalancing kind of action, the land would necessarily in the end disappear, and indeed would have disappeared long ago. But owing to the pushing out of some parts of the earth’s surface by the movements of the heated materials inside, portions of the land are raised to a higher level, while parts of the bed of the sea are actually upheaved so as to form land.
This kind of elevation has happened many times in all quarters of the globe. As already mentioned most of our hills and valleys are formed of rocks, which were originally laid down on the bottom of the sea, and have been subsequently raised into land.
This earth of ours is the scene of continual movement and change. The atmosphere which encircles it is continually in motion, diffusing heat, light, and vapor. From the sea and from the waters of the land, vapor is constantly passing into the air, whence, condensed into clouds, rain and snow, it descends again to the earth. All over the surface of the land the water which falls from the sky courses seaward in brooks and rivers, bearing into the great deep the materials which are worn away from the land. Water is thus ceaselessly circulating between the air, the land, and the sea. The sea, too, is never at rest. Its waves gnaw the edges of the land, and its currents sweep round the globe. Into its depths the spoils of the land are borne, there to gather into rocks, out of which new islands and continents will eventually be formed. Lastly, inside the earth is lodged a vast store of heat by which the surface is shaken, rent open, upraised or depressed. Thus, while old land is submerged beneath the sea, new tracts are upheaved, to be clothed with vegetation and peopled with animals, and to form a fitting abode for man himself.
This world is not a living being, like a plant or an animal, and yet you must now see that there is a sense in which we may speak of it as such. The circulation of air and water, the interchange of sea and land; in short the system of endless and continual movement by which the face of the globe is day by day altered and renewed, may well be called the Life of the Earth.
SUNDAY READINGS.
SELECTED BY THE REV. J. H. VINCENT, D.D.