In following the course of this old shore line a gradual slope is noticed, and if this was a shore line, we must account for this variation in elevation, since the surface of the water is always level. The explanation is to be found in the fact that portions of the earth's surface are gradually rising while others are as gradually sinking. On comparing the old coast line with the level of the present one, we find that the lake has gradually inclined to the south and the west. This change in elevation had its share in determining the configuration of the lake as well as the relief features of the surrounding region. The point of discharge was at Rome, New York, as long as the barrier blocked the regions north of the Adirondack Mountains. As soon as the encroaching warmth of the south had removed this barrier to the level of the Rome outlet, the water began flowing by the St. Lawrence course. True the first outlet was not the same as the present one; but it must have been many times shifted in the course of the retreat of the ice. As a result of this alternate shifting, together with the changing of the level of the lake, there are to be found the markings of numerous shore lines, some of which pass under the present level of the waters. These different variations must of necessity have had a great effect on the work of Niagara River. When the Niagara began to flow, instead of its terminal being nearly seven miles from the escarpment, it was only between one and two miles away, and the surface of the lake was about seventy-five feet higher than now. While the outlet remained at Rome, the eastern end of the lake was continually rising, which caused the waters at the western end to rise over one hundred feet. This placed the shore of Ontario almost at the foot of the beautiful cliff at Queenston and Lewiston. After having occupied this position for a long period, the surface of the waters again fell over two hundred feet, carving an old shore line which is now submerged. After this, various changes of level in the land and shiftings of the ice barrier caused numerous old shore lines to be faintly carved. These changes continued until the present outlet was established and the waters began to flow along the present course of the St. Lawrence. One might think that with these changes all the variable factors of our problem have been discussed; but these same factors also had their effect upon the upper lakes. In a study of the old markings of all the lakes of this region, it seems that the northern shores were continually rising; this, of course, points to an occupation of a more northerly position by the lakes than at present, and also a laying bare of northern parts, and shifting of waters south, or possibly both of these changes at once.