DRAINAGE BEFORE THE ICE AGE.
We have already said that during the ice age river-beds were changed, valleys were filled up, new lakes were made, and waterfalls created. Great as were the changes made by the carrying power of moving ice, still greater were those made in preglacial times; not, however, from the action of moving ice, but from running water. Erosion caused by running water has, probably, during the life of the world, transported more material from place to place, from mountain to valley, and from valley to ocean, than any other agency; chiefly for the reason that it has been so much longer doing its work.
The valley of the Ohio River, a thousand miles or more in length, together with the great number of feeders that empty into it, is an instance of the wonderful erosive power of running water. The valley of the Ohio River will probably average a mile in width at its upper level and, deep as it is to-day, it was much deeper in preglacial times. There is evidence that the whole bed of the river was from 100 to 150 feet deeper than it is at present. This has been determined by borings at different points to ascertain the depth of the drift that was lodged during the glacial period in the trough of the Ohio River. Anyone traveling up or down the river to-day can readily see that it is a great sinuous groove cut down through the earth by millions of years of water erosion, and not only this, but that at some time in its history this great valley has been partly filled, forming on one or both sides of the river level areas—called bottom land. These lands are exceedingly productive, owing to the great depth and richness of the soil.
For many years the writer lived upon one of the rivers tributary to the Ohio and often made trips by steamboat up and down the Ohio River. Traveling along this river a close observer will be struck by the exactness of the stratifications in the rock and in the coal beds to be seen on each side of the river. They match as perfectly as the grain of a block of wood when sawn asunder—showing that these coal beds were formed at an age long before the water cut this sinuous groove. What the water was doing while these coal beds were forming will be brought out in some future chapter. All the rivers that are tributary to the Ohio, such as the Monongahela, the Alleghany, the Muskingum, the Tennessee, the Cumberland, the Kentucky, the Wabash, the Miami, the Licking, the Scioto, the Big Sandy, the Kanawha, the Hocking, and the Great Beaver, besides numerous smaller streams, have their own valleys that have been worn away by the same process, and to a greater depth than they now appear to be. All of the material that once filled these valleys has been carried down by the water filling up the bottom of the ocean and building out the great delta of the lower Mississippi. Mountains have been worn down and carried away by the action of the running water until their height is much lower than in former times. The great lakes, that were enlarged during the glacial period and in some cases wholly created—by the scooping out and damming up of the waterways and by piling glacial drift around their shores—have had some of their outlets raised to a higher level, and others have been created anew.
The old river beds that formerly carried the water that is now drained through the St. Lawrence were eroded by the action of running water to a great depth, as is shown by numerous borings along the valley of the Mohawk and down the Hudson. The salt wells at Syracuse, N. Y., have been put down through glacial drifts and the salt water is found in the bed of the old river. Great bodies of salt are found at that low level, constantly dissolved by the water percolating through the sand and gravel of the glacial drift. This salt water is pumped up and evaporated, leaving the salt—forming one of the important industries of that region. All of the rivers from the Ohio eastward tell the same story, which is that at some remote period the land was much higher above the level of the sea than it is to-day. The bottoms of many of these old river beds are lower than sea-level, but as they were made by running water they must have been at one time above that point.
There is abundant evidence that the earth sinks in some places and rises in others. Along the ridges of some of the eastern mountains are found in great abundance the products of the bottom of the ocean. These evidences show that at some period, when the mountains were formed, a great convulsion of nature raised the bottom of the ocean to thousands of feet above its level. Evidences of this exist in various parts not only of the United States, but of the world.
You ask, If this erosion goes on and the mountains and hills are carried down and filled in to the low places of the ocean, what is the final destiny of the earth that now appears above the surface of the ocean? Evidently if the earth should remain without further upheaval, at some time in the far, far future the land would gradually wear down and be carried off into the ocean and the ocean would gradually rise, owing to its restricted area, until it would again cover the whole earth as it undoubtedly did at one time in the earth's history. This fact need not occasion any uneasiness on the part of those who are living to-day or for millions of years to come.
The problem of building a world and then tearing it to pieces is a very complicated one. There is a constant battle going on between the powers that build up and those that tear down; and this is as true of character-building as it is of world-building. The world has never been exactly alike any two successive days from the time its foundations were laid to the present moment. It seems to be a fundamental law of all life and growth, as well as of all decay, that there shall be a constant change. There is no such thing as rest in nature. The smallest molecules and atoms of matter are in constant agitation. In the animal and vegetable world there is a period of life and growth, and a period of decay and death; and this seems to be the destiny of planets themselves as well as the things that live and grow upon them. Still, science teaches us that with all this turmoil and change nothing either of matter or energy is lost, but that it is simply undergoing one eternal round of change. Does this law apply to mind and soul? Do we die? Or do we simply change?