We are prone to look upon the great wonders of the world as destined to last as long as the earth itself. We do not realise that the mountains, miles in height, are slowly crumbling before our eyes, or realise that the rivers are carrying them slowly toward the sea, filling the lakes and lower portions of land along their courses. These slow but ceaseless forces are continually at work, reducing the surface of the earth to that of a level plain and at the same time depriving the land of its lakes by filling their depressions with silt. The winds and the waters, together with the wearing power effected by frost, are the forces struggling at this great levelling task. The work is partly done; in many of the older regions the lakes and elevations have almost entirely disappeared. Other parts of the land are comparatively new; and it is here that one sees the rough mountain or the deep canyon of the river; sufficient time not having elapsed to wear away the elevation in the one case nor the steep banks in the other. One needs but to look at a relief map of the Niagara district to note the Falls and the outline of the Gorge to see at once that this is a comparatively new region or, at least, that the formative forces which gave it its present characteristics were at the highest stage of their career when the lands to the south had almost reached their present stage. These facts can be observed by any person visiting the Niagara district; it does not require a geologist to trace roughly their course. Questions naturally arise in calculating the age of Niagara. If, as all the facts seem to indicate, this river has had a very recent beginning, what then did it do before it occupied its present course? What will be its final destiny? What will happen when it has worn its Gorge back to Lake Erie? Or will the general level of the land be so changed that the Falls will never recede to the lake? The last and most important of all is: How long has it taken the Falls to grind out the Gorge thus far? This latter question, viewed in its relation to the first one, forms the basis of the present chapter. The great work of the Cataract is going on before our very eyes. The history of this great river is working itself out at the height of its glory, in an age when all can behold. It is the more interesting since it is the only example of the kind known. One can easily look back to the time when the water flowed along the top of the plateau to Lewiston and the Falls were situated at that point. This date, of course, witnessed the birth of Niagara, for, wherever the waters flowed before, they could not have taken this course before the Falls began their work. The day that witnessed the beginning of the one witnessed also the birth of the other. Likewise one can not help looking forward to the day when Niagara shall have accomplished its work, when its waters shall have completely ground the plateau in two, and so drained Lake Erie to its bottom.