In the early geological history of the Delaware it is found that all southern New Jersey lay deep beneath the Atlantic, whose waves broke against the ranges of hills northwest and north of Philadelphia, and an inlet from the sea extended into the great Chester limestone valley behind them. This whole region, then probably five hundred feet lower than now, was afterwards slowly upheaved, and the waters retreated. Subsequently the climate grew colder, and the great glacial ice-cap crept down from Greenland and Labrador, forming a huge sea of ice, thousands of feet thick, which advanced on the Delaware to Belvidere, sixty miles north of Philadelphia. Then there came another gradual change; the land descended to nearly two hundred feet below the present level, and again the waters overflowed almost the whole region. This was ice-cold, fresh water, bearing huge icebergs and floes, which stranded on the hills, forming a shore on the higher lands northwest of Philadelphia. The river channel was then ten miles wide and two hundred feet deep all the way down from Trenton, and a roaring flood depositing the red gravel along its bed. As the torrent, expending its force, though still filled with mud and sand from the base of the glacial ice-cap, became more quiet, it laid down the clays, the stranded icebergs dropping their far-carried boulders all along the route. This era of cold water and enormous floods is computed to have occupied a period of about two hundred and seventy thousand years, and then the "Ice Age" finally terminated. The land rose about to its present level, the waters retreated, and elevated temperatures thawed more and more of the glaciers remaining in the headwaters, so that there came down the last great floods which deposited the "Trenton gravel." The river was still wide and deep, and Arctic animals roamed the banks. Mankind then first appeared, living in primitive ways in caves and holes, and hunting and fishing along the swollen Delaware ten thousand years ago. Occasionally they dropped in the waters their rude stone implements and weapons, which were buried in the gravel, and, being recently found, are studied to tell the story of their ancient owners. The river deposited its gravel and the channel shrunk with dwindling current, moving gradually eastward as it eat its way into the cretaceous measures. The primitive man retired, making way for the red Indian, and the present era dawned, with the more moderate climate, and with again a slow sinking of the land, which the geologists say is now in progress. TRENTON AND ITS BATTLE MONUMENT.