[Illustration: The American Fall, July, 1765. From an unsigned original drawing in the British Museum.] What did the waters of the lakes do before the Niagara began its history? How long has it been at its present work? These are the questions interesting to every one; and by far more interesting to one who is making a study of the formative forces now contributing, and which have contributed to bring about the present characteristics of surface structure. A few important facts exist, and these now are beyond doubt, upon which rest the inferences concerning the age of the Falls. In ancient times the waters of Lake Erie did not find an outlet through Niagara River, so there was no channel ready made for the river when it began its present course. Even after the beginning of the river the upper lakes, Huron, Michigan, and Superior, did not discharge their waters through Niagara. Until comparatively recent times only the waters from Lake Erie discharged through this channel and therefore for many ages only a small fraction of the present volume could possibly have been at work on the Falls. The striking features of the Gorge are modern, and have been very little affected by those agencies which are continually moulding the contours of land surfaces. The inclination of the river's bed has varied greatly with the ages, due to gradual uplifting or depressing of the earth's crust; consequently the current has varied greatly in velocity with these changes. A calculation of the work done by the river during each epoch of its history is indeed fraught with many difficulties. Much investigation, however, has been made along this line and with a rather satisfactory degree of success. Niagara appears to have had a life peculiar to itself; but what is unique in its history, is the presentation of characteristics which in the case of other rivers have long since passed away. Rivers, and especially very large ones, appeal to us as "unchangeable as the hills themselves"; but the truth is, that the very hills and mountains are changing as a result of the forces exerted by water. Niagara, as viewed by the geologist, is unique, not on account of its having a different history than any other river, but for the reason that it had a more recent beginning. The calculation of the life of such a stream is interesting in itself, besides the other great questions settled by the solution of such a problem as the probable number of years that the river shall exist in its present form, the centuries which have elapsed since the ice retreated from this region, and the ascertaining of certain facts concerning the antiquity of man. In order to make a thorough study of these topics, one must take a view of the relief features of the Niagara region, and make a careful review of what conditions existed at the time that this district was covered by the great ice sheet, together with the changes effected during the retreat of the Great Glacier to the north.