Niagara Falls and the History of the Great Lakes, by the writer, and published by the Commissioners of Niagara Falls Reservation, under the presidency of Hon. Andrew H. Green.*

THE BIRTH OF THE GREAT LAKES.-This marks only an episode in the chain of events which are being described, when the waters fell three hundred feet below the Algonquin and Lundy planes. Although the subsidence of the waters was not continuous and left some evidences of temporary pauses, yet the long rest was not reached until they had sunk to the level of the Iroquois beach. By this time the land had risen so high, and, as there were no sufficient barriers, the upper lakes sunk far within their present basins, as is shown on the map (Fig. 14). Still, the waters of these upper lakes discharged by way of the narrow Nipissing Strait.

Lake Erie at this time had its birth, but then it was a very small body of water, as shown on the map. The Niagara district was then covered with a strait expanded into a lakelet, and afterward a river at first without a fall. In the further sinking of the water to the Iroquois level the falls of Niagara commenced their history, and then there was a comparatively long rest, but Ontario was still a gulf, as shown on the map (Fig. 14).

The plane of the Iroquois shore was at identically or nearly the same level as the Nipissing beach (of Taylor) at the outlet of Lake Huron by way of the Ottawa Valley. It is not apparent, and it is theoretically improbable, that the Nipissing River was characterized by more than a gentle slope, for by the time that the land rose high enough to produce a rapid river the water of the upper lakes had changed their outlet into Lake Erie. The proof of these changes rests in the tilting of the beaches, which aggregates several hundred feet (see Fig. 12).

BARRIER TO LAKE ONTARIO. Still, the land has continued to rise, and the deformation since the Iroquois episode amounts to more than before that date. The tilting at the head of Lake Ontario becomes an absolute elevation above the sea, amounting to three hundred and sixty-three feet, and at the northeastern corner of the Adirondacks it is fifteen hundred feet, while near the outlet of Lake Ontario it is seven hundred and thirty feet. This warping of the continent is illustrated in Fig. 15, and to it is due the barrier (to a large extent) which retains the waters of the Ontario basin at an elevation of two hundred and forty-seven feet above the sea.

SINKING AND SUBSEQUENT GROWTH OF THE MODERN LAKES AND CHANGE OF OUTLETS.-The continuing elevation of the con

* The surveys of the deserted shore lines of the lakes have been mostly made by Messrs J. W. Spencer, G. K. Gilbert, A. C. Lawson, and F. B. Taylor.

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FIG. 14.-MAP OF THE EARLY LAKES. Broken shading represents extension of the early lake epoch; solid shading, a lower stage of Iroquois Gulf before the birth of Lake Ontario; modern lakes, by dotted lines.

overflowed. The upper lakes were the first to sink far within depended upon the rims of the lake basins from which the waters tinent lowered all the waters of the lake region until their levels

their basins (see Fig. 14), but later even the Iroquois Gulf was contracted so as not to occupy even the head of the present Ontario basin (see Fig. 14).

The great deformation of the whole region since the close of the Iroquois episode has from that day to this been slowly raising the northeastern rims of the lake basins so as to cause them to flood more and more the lowlands and valleys at their southwestern extremities, and even to raise the waters so high as to cover some of the deserted shores in those directions. At the same time the waters are leaving their old margins at their northeastern ends, as shown on the map (Fig. 14).

The changes have not been quite simultaneous in the different basins, as the heights of the lake barriers and the rate of terrestrial movements have not been uniform. Thus, in terms of Niagara Falls, it is estimated that the Iroquois Gulf sank below the Iroquois plane about fourteen thousand years ago; but that the

FIG. 15.-SECTION SHOWING THE TILTING OF THE IROQUOIS BEACH SOUTH OF LAKE ONTARIO AND THE ST. LAWRENCE RIVER as far as thE NORTHEAST Corner of thE ADIRONDACKS.

waters of Lake Huron, which had been emptying by way of the Nipissing Strait for twenty-four thousand years, were turned into Lake Erie only eight thousand years ago. Again, after the waters of the Ontario basin had sunk much below the present western margin of the lakes, they were rising again to near their present height only some three thousand years ago.

Of the absolute amount of rise of the continent we do not know, for the axis of uplift has not been ascertained, but it is evidently in the interior of the continent. The differential rate of elevation varies, being about a foot and a quarter a century in the Niagara district, two feet northeast of Lake Huron, and nearly four feet north of the Adirondacks.

THE FUTURE DRAINAGE OF THE UPPER LAKES INTO THE MISSISSIPPI RIVER.-With the land rising as at present, it will be only a matter of time until the northeastern rim of Lake Erie will be so high that the drainage must turn into Lake Huron, and thence by way of Lake Michigan and the Chicago Canal into the Mississippi, and Niagara Falls will then end their life history. Some fifteen hundred years ago there was a barrier about a mile north of the present site of the falls that had risen so high in the general regional uplift as to actually cause some of the waters of the upper lakes to overflow where the Chicago Canal is now being built; but, owing to the peculiar buried valley just behind this ridge crossing Niagara River, when the falls had passed the barrier, before the change of outlet of the upper lakes from the Ni

agara to the Mississippi was completed, the upper lakes were rapidly lowered, and this re-established the life of the Niagara for some time longer. Upon the basis of calculations made it would appear that the change of outlet for the upper lakes from the Niagara to the Mississippi will not be more than another five thousand years hence to us living a matter of indifference, but only showing how the present days are simply passing events in the history of the lakes. In the meanwhile the waters of Lake Ontario will more and more flood the head of its basin. However, the end of the lakes is so far removed in geological time that, until such great changes in the configuration of the land shall have obtained of which we have no prophetic vision, the lakes will continue to exist.

AGE OF THE GREAT LAKES.-When the rate of movement of the earth's crust, as determined in the history of Niagara Falls, is applied to the deserted strands of Warren Water and its successsors, it is estimated that since the commencement of the Warren epoch fifty thousand or sixty thousand years have elapsed. This estimate, although based upon the most analytical knowledge obtainable, can, after all, be regarded as only approximate. The time ratio tells us that the lakes are still youthful; although in terms of solar years very old, yet perhaps not older than the human race.

The vicissitudes between the end of the ice age proper and the birth of Warren Water are too little known to enter into any proportional division of time, except that the ice age culminated prior to or at the date of the closing of the old valleys with drift.

The Great Lakes are the most striking feature of the eastern part of the continent, yet what we know of their history has been mostly discovered within the last few years. In this sketch only some of the more important and generalized results have been given. Many of the observations are beyond doubt, but there is plenty of room for students to add to our knowledge and correct our imperfect work. While the history of the lakes can be told with considerable certainty, the attempt at computing their age in terms of solar years has the same fascination, although not so extravagant, as the speculations concerning the antiquity of the earth itself, as the former question probably comes within the human period.

HARVARD College Observatory publishes a list of fourteen new variable stars of long period, in addition to those previously announced, which have been discovered by Mrs. Fleming from the examination of Henry Draper memorial photographs. The spectrum of one of these stars is of the fourth type, while all the other stars have spectra of the third type, with the hydrogen lines also bright.