Some years before this discovery was made there were terraces found along the banks of the Ohio River and its tributaries that had been the subject of much speculation. It is well known that by the action of water from rainfall, earth, gravel, and other débris will wash down the side of a hill or mountain until it strikes a water level, and there it will build out a terrace near the level of the water surface. The width of these terraces will be determined by the time the water has stood at that level and the extent and nature of the soil from which the débris comes. The evidences that are cited, pro and con, would fill a small volume, but it is sufficient to say here that the sum of the evidence goes to show that there was an ice dam formed at a point near Cincinnati and that it was maintained for a considerable period of time. Terraces were formed running up the Ohio and its tributaries corresponding to the level that the water must have risen to if the valley were filled up with ice. These facts, taken with the greater fact that the ice sheet actually did cross the Ohio Valley into Kentucky, as is shown by the terminal moraine, seems to prove conclusively the existence of such a lake during the period that the ice rested at its extreme limit. The fact that in some places successive terraces are found does not disprove the theory, because it is more than likely that when the ice receded it did so in successive stages, remaining at different positions for a considerable length of time. There is abundant proof of this in the successive moraines and also in the formation of successive terraces. Some of these terraces could have been formed from other causes. It does not require any great stretch of the imagination to understand how numerous lakes, much larger than any at the present day, may have extended over large portions of the West and Northwest during the period that the ice was receding. The ice did not stand with an even thickness over the surface of the glaciated area, but at some points it moved down in great lobes, which marked the lines of greatest pressure as well as the greatest accumulation. As the ice melted away, the thick bodies of ice might be many, many years in melting, and they might block the outlet to a very extensive drainage area and thus form a great inland sea from the vast amounts of water that would come from the melting ice.