or more, and reduce the descent of the river by eighty feet or

more.

EPISODES OF THE NIAGARA RIVER AND THEIR DURATION.— At first the river flowed without falls, as shown by the old banks and terraces, for a period estimated at at a thousand years. Then the waters of the lower lake began to subside, whereupon the Niagara Falls had their birth. The new cataract slowly grew in height, although characterized by temporary pauses, until the river cascaded two hundred feet from the tableland into the edge of the gulf or lake which occupied the Ontario basin, as shown in Fig. 16.

The volume of the water of Lake Erie is about one fourth that of all the upper lakes, and only this proportion of the discharge of the modern Niagara River formed the abrading agent of the falls at that early date. This general condition lasted for seventeen thousand two hundred years. After this episode, the descent of the river was increased to four hundred and twenty feet, and the lake receded twelve miles from the foot of the mountain, and then there was a series of three cascades, the lower always gaining upon the upper on account of the softer rocks. Yet the increased amount of work to be done, even though easier than the recession

*For the methods of computation of the duration of the episodes of Niagara Falls see

FIG. 16.-LONGITUDINAL SECTION, SHOWING THE RETREAT OF THE FALLS AND THE GEOLOGICAL STRUCTURE. A, Brow of escarpment and original site of
falls; I, Iroquois beach and level of that water; Bb I, chasm at the end of the first episode; C c h g, falls retreating in three cascades, but from h to g
the slope was extended over a distance of twelve miles beyond the escarpment; D d m g, position of cataracts at the end of the second episode;
E e g, development of gorge at the end of the third episode; F, present site of falls, and F m g, the modern cañon; g, level of the lowest stage of
water in the river history; L, Lundy beach capping the drift; J, Johnson's ridge. Broken shading about whirlpool shows occurrence of drift on west
bank only with rock on the eastern; block shading represents limestone; dotted, sandstone; broken lines and unshaded portion, shales. Bottom of
river eighty feet below present surface of Lake Ontario, as shown in figure.

Duration of Niagara Falls and the History of the Great Lakes, pp. 1-126, 1895. Also see Duration of Niagara Falls, American Journal

of Science, December, 1894, pp. 455-472-both works being by the writer.

of the upper cascade, prolonged the episode to six thousand years, when Foster's Flats were passed. By this time the waters of Lake Huron were probably turned into the Niagara by way of Lake Erie. With the increased magnitude of the river the falls are thought to have receded as far as the head of the whirlpool, requiring four thousand years. By the close of this stage there were some important changes in the river, as when the narrows of the whirlpool rapids were excavated, and the three cataracts of the second episode appear to have been united into one great fall. With the increased volume of water at the maximum height of the falls, as at the apex of the modern horseshoe cataract, the recession was very rapid, so that the falls receded to above the railroad bridges in eight hundred years more. It was in the next episode that the descent of the river was reduced from four hundred and twenty feet to three hundred and twenty-six feet, which is that of the present day. These changes of height of falls and volume of the river must not be supposed to have been sudden, and, although they were secular, yet there were long periods of rest, as shown by the landmarks, which are mostly obliterated where they were imperfectly engraved during short epochs of repose. The first stage of the last episode is characterized by the retreat of the falls through the great rocky barrier (Johnson's Ridge, e e, Fig. 9) on the northern side of the buried Tonawanda Valley. Beyond this barrier the river speedily removed some ninety feet of drift for a distance of a mile and a half to the head of the rapids above the horseshoe cataract, and the recession across the buried valley has been the last stage of the present episode of the falls. Here the necessary time for the retreat of the falls since passing the railway bridges has been three thousand years.

Adding the duration of the various stages of the river together, the age of the falls is computed at thirty-one thousand years, or of the river thirty-two thousand years. These figures are based upon the severest analytical methods at present attainable, but the discoveries in the physics of the river cover most of the doubtful points; yet in the determination of the amount of work performed in the middle episodes some points are open to revision, but the errors they cover form only a small portion of the life of the cataract, and a little time, more or less, would not greatly change the results given. No general guesses or objections have been found worthy of consideration. The determinations had to be attempted in parts, and the aggregate results have been confirmed by two other sets of investigations: one on the relative amount of tilting of the deserted shores, and the other upon the rate of the rising of the land in the Niagara district, which has been found to be about one foot and a quarter a century, but much more rapidly to the north and east.

NIAGARA FALLS NARROWLY ESCAPED EXTINCTION.-Fifteen hundred years ago the terrestrial movements raised the Johnson barrier to the Erie basin so high that the waters of that lake reached not merely the level of Lake Michigan, but the point of turning all the water of the upper lakes into the Mississippi drainage by way of Chicago. But the falls were then cutting through the ridge, and when this was accomplished, before the change of drainage was completed, the surface of Lake Erie was suddenly lowered by many feet, and thus the falls were re-established for some time longer.

DEATH OF THE FALLS.-Slowly, year by year, one sees the cataract wearing back and suggesting the time when the river will be turned into a series of rapids; but another silent cause is at work, and one not easily seen-namely, the effects of the changing of level of the earth's crust. From the computations already referred to it was found that for the first twenty-four thousand years of the life of the river only the Erie waters flowed by way of the Niagara River, and for only eight thousand years have all the waters of the upper lakes been feeding the falls. If the terrestrial movements continue as at present, and there appears no reason to doubt it, for the continent was formerly vastly higher than now, then in about five thousand years the rim of the Erie basin promises to be raised so high that all the waters of the upper lakes will flow out by way of the Chicago Canal. Thus the duration of Niagara Falls will have continued about thirty-seven. thousand years. But the lakes will endure beyond the calculations of the boldest horologist.

RELATION OF THE FALLS TO THE ICE AGE.-In telling of the times of the great mutations in the physical history of the lake region, the story of Niagara Falls seems completed, but as a timepiece they are much more important in being used as a stepping stone back to the great period of frost which separated the former order of the continent from the modern. Having ascertained the approximate amount of the rising of the land recorded in the deserted beaches, before and since the birth of Niagara Falls, and the rate of the rising of the land, and applying it to the movement recorded in the abandoned shores, it is concluded that the epoch when the lake region formed great expansions of more or less open water commenced fifty or sixty thousand years since. Going so far back in time, other conditions may have obtained to vary the rate, but these have been allowed for as far as possible.

Beyond the lake epoch the vicissitudes between the periods of great regional submergence and the earlier high continental elevation of the ice age proper are apparent, but the events are certainly unexplained, for what was done by glacial action and what by waves has not been determined. Niagara Falls

VOL. XLIX.-2

shows that the end of the Glacial period in the lake region was long ago.

HOW NIAGARA FALLS MAY BE USED TO ASCERTAIN THE ANTIQUITY OF MAN.-The relation of Niagara Falls to the deserted shores of the lake region and the high terraces is now pretty well known, and the old water margins have been traced over wide areas; but these may be much further extended and their relations to other regions beyond the drainage basins of the Great Lakes be ascertained, so that we may hope that Niagara Falls may be used as a means of at least roughly estimating the age of the deserted river banks on which the oldest inhabitants left their scanty treasures long ago. Concerning this application, it seems as only a question of the work of so many men and so much time. To the geologist, the birth, life, and death of Niagara Falls show no more rapid changes than come within the limit of modern observations. There have been no sensational catastrophes, although in the popular mind these changes come with new and startling revelations, so that the most conservative observer may be surprised. The changes in the history of Niagara have now been told, so far as we know them. We can still watch the river performing its wonderful amount of work and the slow recession of the falls, as shown in Fig. 17.

If the reader of this sketch of the history of Niagara Falls desires the fuller information upon which this study is based, he is referred to Duration of Niagara Falls and the History of the Great Lakes, by the present writer, whose labors have been brought together by the Commissioners of Niagara Falls Reservation, under the presidency of the Hon. Andrew H. Green, whose liberal policy is not merely to preserve the falls as an international park, but to make known their scientific history.

In the ascension of the balloon Phenix, made from Stassfurt, Prussia, in December, 1894, the weather being misty at starting, the temperature at first increased up to a considerable height, but afterward fell, and at 32,150 feet stood at -20° C. At about 29,500 feet the balloon passed through a veil-like stratum of cirrus clouds, consisting of perfectly formed flakes of snow. At 31,500 feet the thermometer dropped to -54°, and indicated only -11° in the sun's rays. The highest temperature recorded was 43°. During the ascent of three hours and the descent of two hours and twenty minutes the balloon traveled one hundred and eighty-six miles, although it was almost calm at the surface.

OBSERVING the growth of bamboos in the Botanical Garden of Buitenzorg, Java, Mr. Gregory Kraus noticed one plant which added to its length 22.9 centimetres a day for fifty-eight days. Another plant grew 19.9 centimetres, and a third nineteen centimetres a day for sixty days. The longest single day's growth observed was 42:45 centimetres.