Popular Science Monthly/Volume 45/June 1894/The Cincinnati Ice Dam
By G. FREDERICK WRIGHT,
PROFESSOR OF THE HARMONY OF SCIENCE AND REVELATION IN OBERLIN COLLEGE.
IN many respects the Ohio is one of the most remarkable rivers in the world. Its drainage basin comprises about two hundred thousand square miles on the northwestern slope of the Alleghany Mountains. Its eastern tributaries rise at an elevation of something over two thousand feet above the sea, and hence are so situated as to carry the rainfall and the melting snows with great rapidity into the main channel, which at Pittsburg is seven hundred feet above the sea, and at Cairo, where it unites with the Mississippi, about three hundred feet; the descent from Pittsburg to Cairo being about four hundred feet in a distance, as the river runs, of nearly a thousand miles.
The whole course of the river is through sedimentary rocks, which, though of Palæozoic age, have been but slightly disturbed. The elevation of the region has been so continental in its proportions that the rocks have retained to a great degree their original THE CINCINNATI ICE DAM. 185
horizontal position. Through these comparatively horizontal strata the Ohio River has worn a gorge of remarkable uniformity, and several hundred feet in depth. Even to the ordinary observer it is clear that this trough is one of erosion ; for the strata of rock upon one side of the river match those upon the other as precisely as do the two ends of a board which has been sawed apart. The seams of sandstone, coal, and lime rock upon one side correspond to similar seams upon the other ; while the river does not pursue a straight course, but follows, throughout, a very tortuous chan- nel, such as is begun by the meandering of a stream over a nearly level surface.
The width of this rocky gorge is from a quarter of a mile, where the rocks are peculiarly hard, to a mile or over, where they are more easily disintegrated. For the most part, also, the tribu- taries occupy corresponding gorges, with a width contracted to the proportion of the individual drainage basins. At the junction of the main stream with the tributaries there is usually an en- largement of the gorge such as would naturally follow from the combination of erosive forces which there occurs. These features of the trough of the Ohio and its tributaries give character to the scenery throughout its course. Nowhere from the decks of the steamer does one get an extended view on either side. Every- where the vision is circumscribed by the hills, more or less pre- cipitous, which rise close at hand upon both the right and the left ; while the windings of the channel are such that no very dis- tant views are obtained either before or behind. The railroads which connect the cities in the valley are compelled either to hug the side of the gorge between the river and the precipitous ledges, or to strike up some one of the tributaries, and then, after cross- ing the country for a while, follow down another to the level of the main stream. The land a little back from the trough of the river is very broken and hilly, since all the affluents of any size have eroded channels for themselves down to the depth of the princi- pal gorge.
Above Louisville, Ky.,the large cities upon the Ohio strikingly reveal the limitations imposed upon them by the character of the river valley. Having begun as a cluster of houses upon the river's bank, they have gradually spread back upon it, until reaching the base of the rocky precipices. With the rapid growth both of population and of improvements in later years, Cincinnati and Pittsburg have literally overflowed their banks and risen to the summit of the hills on either side, the inhabitants being transported from their places of business to their residences by long inclines up which the street cars are drawn at a steep angle to a height of from three to five hundred feet, from which positions extended views are given in every direction over the
VOL. XLV. 14
Map 1, showing the 500-foot and the 1,000-foot contours of the Ohio Valley; also the boundary of direct glacial action and the approximate limits of the slack water produced by the Cinicnnati dam. The figures give the elevation above the sea. Those along the river refer to the low-mark. In the lower right-hand corner is a typical section of the Alleghany, showing the rock channel and the high-level terraces.
broken surface whose summits represent the once comparatively level area. At Parker City, Pa., an elevator was once used to lift foot travelers from the lower terrace to the upper terrace, two hundred feet above.
Although flowing in so deep a trough, the present Ohio River is considerably elevated above the ancient bottom. This is owing to the fact that during the Glacial period such an excessive amount of gravel was brought down from the Alleghany River and other northern tributaries that the old channel was silted up to a considerable depth. At Cincinnati there is more than one hundred feet of gravel between the present river bottom and the rock bottom. Below the mouths of the most important northern tributaries the accumulations were much greater than this. At Cincinnati the channel was choked with gravel from the Little Miami to a height of one hundred and twenty feet above the present river. Subsequently this was partly eroded away, leaving the one-hundred-and-twenty-foot gravel terrace which is now oc- cupied by Fourth Street.
It is fortunate for civilization that there are left along the trough of the Ohio numerous remnants of this high-level glacial terrace ; otherwise the cities would be even more subject to damage from floods than they are now ; for the Ohio River is subject to greater fluctuations of level than almost any other stream in the world. During the flood of 1884 the water rose at Cincinnati seventy-one feet, submerging the railroad stations and much of the lower part of the city, but leaving that portion which was upon the glacial terrace fifty feet above water. The cities which were not favored with so marked a gravel terrace, or had not taken advantage of their opportunities, were for many days turned into miniature Venices, the lower stories of the houses being generally submerged by the muddy torrent, and boats being able to pass freely through all the streets.
The cause of these enormous floods along the Ohio is readily perceived ; for, as already remarked, the slope of the streams rising along the summit of the Alleghany Mountains and flowing into the Ohio is so rapid that the water from the rains and melting snows finds its way into the main trough of the river in an incredibly short time, while the trough is so narrow in places, especially just below Cincinnati, as greatly to impede the progress of the current. Two or three inches of rainfall over two hundred thousand square miles provides an enormous quantity of water, which, upon being suddenly transferred to the river channel, turns a stream which can sometimes be forded in dry weather into a steadily advancing column of water one thousand miles long and from fifty to seventy-five feet deep. It is interesting to watch from the weather bulletins the progress of the waves that move down the
�� � Ohio upon the unusual rise of any of its upper tributaries. At Pittsburg thousands of coal barges collect during low water to take advantage of these waves of translation, and move forward upon them with their valuable freight like a vast army to supply the great cities of the Mississippi Valley with fuel. But, as with
Fig. 1. — Jasper Conglomerate Bowlder, Three Feet in Diameter from North of lake Huron. Found near Union, Boone County, Ky. (See Map II.) From photograph by the author, reproduced in The Ice Age of North America, p. 328.
everything else, the best gifts of Nature are those which come in moderation. Enough is better than more. Excessive floods interfere with navigation as effectually as does a lack of water.
With these facts in mind, while surveying, in the year 1882, the glacial boundary across the Mississippi Valley, I reached Cincinnati, having traced the border line to the river twenty-five or thirty miles above the city. Upon crossing to the general level of the hills in Kentucky, I found various indubitable evidences that the ice had extended across the trough of the Ohio, and left its marks several miles south of the river over the northern part of Boone County, and up to an elevation of more than five hundred feet above low-water mark. This was along the watershed between the Licking and Ohio Rivers, which was continuous at this height to the central part of Kentucky. Among other evidences one of the most conspicuous was a bowlder of jasper conglomerate, three feet in diameter, found near Union, in Boone County, which was subsequently transported to Chicago as a part of the Ohio glacial exhibit at the Columbian Exposition. Its right to have a place in an Ohio exhibit was due partly to the fact that it was discovered by an Ohio man, but chiefly from the fact that, at the snail's pace at which a glacier moves, this bowlder must have been in the territory of Ohio for an enormous period of time, long enough for even a bowlder to become naturalized. If, however, the Canadians should claim it as a fugitive from justice, they would have a prior right, for the ledges from which it was derived are near Thessalon, in Ontario, north of Lake Huron. In searching for bowlders in southern Ohio, I was accustomed to hear them referred to as "niggerheads." In the progress of discovery it was found that the numerous articles of that description which in recent times Kentucky had furnished to Canada were in payment of a debt under which the Dominion had placed the southern commonwealth long ages before.
It is important to note that my discovery of Canadian bowlders on the hills of Kentucky was not the first which had been made there. As far back as 1845 Prof. Locke had noted the post-glacial conglomerate called Split Rock, below Woolpert's Creek, opposite
Fig. 2. — Split Rock, near Mouth of Woolpert's Creek, Ky. This is part of an extensive deposit of bowlders and gravel with some Canadian pebbles, all cemented together by infiltrated carbonate of lime. From photograph by the author, reproduced in The Ice Age of North America, p. 345.
Aurora, Ind., but had regarded this as the remnants of local strata which had been nearly worn away. In 1872 also, Mr. Robert B. Warder had suggested that this was possibly a terminal moraine. Still later Dr. Sutton, in 1876, and Prof. Cox, in 1878, had noted similar deposits near the summit of the Kentucky hills, on Middle Creek opposite Aurora, and had attributed them correctly to glacial action during the maximum stage of the great 190 THE POPULAR SCIENCE MONTHLY.
Ice period. But because of the imperfect knowledge of the glacial geology of the valley possessed at that time, these discoveries attracted little attention. Various causes, however, conspired to give a somewhat extraordinary notoriety to the facts as they were presented at the meeting of the American Association for the Advancement of Science at Minneapolis in 1883. At that time a systematic exploration of the glacial boundary had been conducted from the Atlantic Ocean to Cincinnati, showing that the Ohio River lay for the most part considerably south of the farthest extension of the ice. Also attention was then first called to the full extent to which the ice had crossed the river in that vicinity. For a distance of nearly one hundred miles it was now demonstrated that the ice came down to the north margin of the trough of the river, and for much of that distance crossed it and mounted the hills upon the opposite side, reaching at one point fully ten miles upon the high land beyond the river. This could not well help suggesting the formation of an ice dam at Cincin- nati which would set the water back up the Ohio and its tribu- taries to the level of the watershed between the Licking and the Ohio, thus forming a narrow and tortuous lake several hundred miles long, which would be five hundred feet deep above Cincinnati and two hundred and fifty feet deep at Pittsburg. (See Map I.)
Finally, some of the geologists who had been engaged upon the survey of western Pennsylvania at once came forward and affirmed that such an obstruction as this supposed at Cincinnati helped to explain a great number of facts respecting certain high- level gravel terraces characterizing the Alleghany and Mononga- hela Rivers, which were surprisingly near the level of the water of the supposed glacial lake. At the meeting at Minneapolis Prof. Lesley, under whose vigilant eye the recent geological sur- vey of Pennsylvania has been conducted, declared that he had for some time been expecting the discovery of a local obstruction to the drainage of the Ohio River which would account for the gravel terraces on the Alleghany and Monongahela to which reference has been made, and now, says he, Providence has pro- vided it, and Wright's dam clears up the whole problem, or words to that efi'ect.
Such was the boom with which the theory of the Cincinnati ice dam was brought before the public in 1883. During the ten years which have since elapsed, the hypothesis has been subject to much criticism, so that the faith of some has been shaken, and the theory itself is thought by many to be left in rather a dam- aged condition. The fullness with which the main facts have been already presented makes it possible to tell the remaining part of the story and state the present condition of the theory in few words.
�� � So complicated are the forces of Nature that one discovery is sure to lead to another, and the man of science soon learns that he never exhausts attainable knowledge even in respect to the simplest subject, and the student has made little true advancement if he has not acquired ability to hold his mind wide open
Map II, showing the partly filled preglacial channel of the Ohio, extending from Cincinnati to the Big Miami at Hamilton. The figures show elevations above the sea.
for the reception of any and all additional facts which may modify and enlarge his theories. In the present case most interesting additions to our knowledge of the facts were made by Prof. Joseph F. James, who called attention to the breadth and depth of the valley running northward from Cincinnati to Hamilton, on the Great Miami River, and to the comparative narrowness and 192 THE POPULAR SCIENCE MONTHLY.
shallowness of the present rocky gorge of the Ohio between Cin- cinnati * and the mouth of the Great Miami. The relative nar- rowness also of the latter opening between the rocky escarpments is readily visible to the transient traveler. Mill Creek Valley be- ing about twice as wide as that of the Ohio for fifteen or twenty miles below the mouth of the creek ; while a low passage joins Mill Creek at Ludlow Grove which sweeps around north of Wal- nut Hills, and enters the Ohio through the valley of the Little Miami Walnut Hills, Mount Auburn, and Mount Lookout, the principal residence portions of the city, being upon a high, rocky pedestal completely surrounded by a depression which has at some time been produced by river erosion.
This valley from Cincinnati to Hamilton is now filled with gravel and clay to a great depth. Upon inquiring for the extent to which the old channel had been filled, it was found by the wells which had been sunk in it that the rock bottom descends from Cincinnati to Hamilton, and is considerably lower than the rock bottom of the present Ohio below Mill Creek. Near Ludlow Grove the bed rock is at least sixty feet below present low water in the Ohio. A few miles farther north, at Ivorydale, on Mill Creek, the bed rock where reached was found to be thirty-four feet below low-water mark in the Ohio, while there was nothing to show that in other portions of the valley the gravel was not still deeper. At Hamilton the bed rock was found to be at least ninety-one feet below the bottom of the Ohio River, showing that there is a deeply buried channel through Mill Creek Valley from Cincinnati to Hamilton ; while, according to the inspector, Mr. C. J. Bates, upon building the piers for the great bridge of the Cin- cinnati Southern Railroad, which crosses the Ohio River near the west end of the city, it was found that the rock bottom was everywhere within a few feet of the low-water mark ; thus fully justifying the inference of Prof. James, which can best be given in his own words :
"... Previous to the Glacial period a barrier of land extended from Price Hill on the north to the mouth of the Licking River on the south, preventing the westward flow of the Ohio, and forc- ing it north and northwest along the channels of Mill Creek and Duck Creek. These met at Ludlow Grove (near Cummingsville) and together continued north to Hamilton. Here entered the Great Miami, and the united streams continued in great volume southward to the present channel of the Ohio, at Lawrenceburg.
" At the coming on of the Glacial period a tongue of ice pro- jecting down the valley from the north and surrounding the Cin- cinnati Island, as we may call that high land now covered with
- See Map II.
�� � THE CINCINNATI ICE DAM, 193
suburban liomes, forced the water of the Ohio southward, over the watershed of the Licking, possibly into what is now the Ken- tucky River gorge. This course was pursued for an indefinite period ; but, when the ice had retired, the river returned to its own channel near Cincinnati. Finding, however, its outlet to the north choked by debris of the glacier, and the former barrier of land between Price Hill and the mouth of the Licking lowered or cut away, it followed the line of drainage it holds at the present time.
" If the eye of savage man gazed upon the site of Cincinnati before the age of ice, he beheld a vastly different scene from what he would behold now. Standing on the highest point of Mount Auburn [Walnut Hills], he looked south over a deep, rocky gorge, through which rolled the mighty Ohio. On the west was the rocky shore of Price Hill extending in an unbroken line north and south to Kentucky. The Licking River entered as a tribu- tary here. On the east was another waste of water rolling its dark tide northward, and joining the western branch beyond the hills of Clifton. No broad expanse of valley nor of rolling plain lay beneath him ; no city was there, teeming with life and hum- ming with industry ; no railroad trains were panting and puffing, holding their way toward sites of unknown towns. But the water swiftly, with sullen roar re-echoing from cliff to cliff', pur- sued its journey toward its unknown grave. No steamer plowed its waters, but dugout or canoe probably carried primitive man from camp to camp or shore to shore. Where once the imagi- nary savage stood are now jjalatial mansions. Where once the waters spread their turbid tide is now a busy city of four hun- dred thousand people. The water which was once cleft only by the prow of frail canoe is now a highway for many floating palaces. Where once the stream pursued its northward course, the iron horse carries thousands daily to and from their homes in the wide and fertile Mill Creek Valley. Never would all this have been had not the Glacial period wrought its wondrous change. But the ice filled the valley and forced the river from its course. When permitted to return, the ancient channel was so filled with debris that a new one must be cut out, leaving the old one to 1)e utilized by man as a way for his iron servant and as a place whereon to build his cities." *
An inspection of the general map (Map I) will show that this ancient deflection of the Ohio by way of Hamilton is in analogy with the course of the river in many other i)laces, as at Beaver, Pa., and below Marietta, Ohio, and that Prof. James's discovery of the buried channel, showing the ancient deflection by way of
- Journal of the Cincinuati Society of Natural History, July -October, 1888, pp.
VOL. XLV. 15
�� � 194- THE POPULAR SCIENCE MONTHLY.
Hamilton, adds greatly to the significance of the ice obstruction at that point, for it extends the distance of it about fifty miles, and the distance covered by the ice beyond the original river bed twenty miles.
While every attempt to calculate the chronology of the Glacial period is necessarily but approximate, still we can get from cer- tain data a pretty good idea of the relative periods of time occu- pied by different stages of the advance and retreat of the ice. It is clear that the obstruction of the Ohio near Cincinnati con- tinued during the whole time occupied by the advance of the ice from Hamilton to its farthest point, ten miles southwest of Cin- cinnati that is, during the advance of the ice front over a space of about thirty miles and until its retreat to Cincinnati again. The only statement approaching to definiteness which we are warranted in making concerning the rate of this advance is that it was probably the slowest which we should assign to any part of the movement of the great continental ice-sheet ; for, being near the extreme point of extension, the equilibrium of forces must have been very nearly established, and the momentum of the glacier from the north was constantly diminished at the front by the increased rapidity with which a more genial climate was melting the ice. So to speak, the glacier was here getting upon doubtful territory and had carefully to consider every forward step, until finally, having reached the height of the Kentucky hills, the balance was turned, and the retreat began. It is alto- gether probable that this close balancing of forces resulted in an exceptionally slow movement from Hamilton to Cincinnati, caus- ing the glacier to occupy many centuries, or even thousands of years, in that part of the march.
Something of a measure of this time is perhaps to be found in the erosion of the cross-cut from Cincinnati to the mouth of the Great Miami, which must have begun as soon as the obstruction of the valley near Hamilton first occurred. The length of this new channel of erosion is from twelve to fifteen miles ; but how much of the work had been previously done by the small streams formed by the local drainage it is difficult now to calculate. Many such questions remain to reward the labors of local investi- gators. The general impression which I have received from a study of the facts is that a period of several thousand years maj^ have been occupied by the ice-front in its advance from Hamilton to the farthest point in Kentucky and its subsequent retreat to the north side of the river.
But it is not to be supposed that this period was by any means one of dull uniformity in the history of that region, for upon the first formation of the dam at the bend of the old river at Hamil- ton, raising the water to the height of the rock obstruction across
�� � THE CINCINNATI ICE DAM. 195
the present gorge of the Ohio just below Cincinnati, the river would at once begin the process of cutting down its new channel. A waterfall of far larger proportions than Niagara must have been at once developed in the lower portion of this short cut, near the junction with the Great Miami, which would steadily wear back toward the old channel at Cincinnati, when, if the ice had not reached so far, the water level above the dam would be speed- ily lowered, but only to be raised again at a later time when the advancing ice reached its farthest extent and obstructed the newer channel. It is altogether probable, however, that this new chan- nel below Cincinnati had not been lowered to its full extent be- fore the maximum advance of the ice. If this were the case the final retreat of the ice across the river would leave a rocky bar- rier below Cincinnati, such as to maintain the water for a while at a level much higher than that maintained at the present time. There are some deposits up the riyer indicating that this was the case, as, for instance, some in Teazes Valley extending from the Kanawha River to Huntington. By reference to the first map it will be perceived that this valley is less than seven hundred feet above tide, but it is covered with several feet of very fine sedi- ment, distributed evenly over the bottom of the valley, which must have been deposited in still water during the later stages of the Glacial period.
A glance at the first map will also show some other most inter- esting problems of change in drainage systems caused by the Gla- cial period which have not been adequately studied ; for example, it will be noticed that a stream rising near Madison, Ind., pursues a very singular course with reference to the contour lines. This is the Muscatatuck River, which rises within less than a mile of the Ohio River and four hundred feet above it ; but instead of following the strike of the strata, as it naturally would, around to Louisville, it cuts across a broad north-and-south valley of ero- sion to join the East Branch of the White River, when both to- gether, continuing on in a westerly course, follow a gorge several hundred feet deep through the highest portion of the State till they unite with the West Branch of the White River to reach the Ohio through the Wabash. It is extremely difiicult to explain the course of this stream, except by some such process of reasoning as has been adopted with respect to the Ohio below Cincinnati. The projection of the tongue of ice which extended below Madison de- flected the drainage of a considerable region through a j^artially formed pass across the elevated plateau to the west, while the morainic deposits about the farthest extension of the ice lobe per- manently obstructed the channels in that direction, so that upon the withdrawal of the ice the Muscatatuck still continued to run into the Ohio by way of the Wabash.
�� � 196 THE POPULAR SCIENCE MONTHLY.
As lias been said, the first announcement of the Cincinnati ice dam was thought to give a natural and sufficient explanation for certain high-level gravel terraces occurring in the upper Ohio Val- ley. Subsequent investigations have brought to light other con- siderations which must more or less modify the first conclusions. It still remains true, however, that the ice dam accounts most naturally for many of the slack- water deposits which occur in the valley of the upper Ohio and its tributaries, while there are many areas which are yet but inadequately explored, but which promise important light upon the problem when the facts are all obtained. At the same time it appears that some of the terraces in the Alle- ghany and Monongahela Rivers are slightly higher than the ob- struction at Cincinnati, compelling the advocates of the ice-dam theory to suppose some very probable changes of level since the deposition of the terraces which were at first supposed by Prof. Lesley to be so completely explained by it.
But more important is the bearing of recent discoveries upon the extent to which glacial gravels accumulated in the gorge of the upper Ohio and Alleghany Rivers, as shown in the section in the lower right-hand corner of Map. I. All along the Alleghany and Ohio Rivers there are remnants of gravel accumulations, from fifty to sixty feet deep, resting upon rock shelves about three hundred feet above the present rock bottom of the Ohio. There is now little reason to doubt that during the Glacial period the floods of water which poured into the Alleghany and the Ohio from all their northern tributaries brought along silt, gravel, and bowlders enough to fill up this rocky gorge with great rapidity, down as far probably as Wheeling. As the Alleghany River received glacial floods and glacial debris in great quantities, while the Monongahela did not receive any, it will be seen that the Monongahela must have been dammed by both the silt and the water which came down the Alleghany.
Instances in which the water of a tributary is dammed by that of the main stream will occur to any one upon a little reflection. "Whenever one large tributary perceptibly rises, it raises the water level of the main stream as well above as below the junc- tion, while a large rise in the main stream may temporarily re- verse the current in a tributary. The Columbia River, for exam- ple, in Oregon, is subject to very extensive floods at seasons of the year when the Willamette is comparatively low. At such times a current sets up stream past the city of Portland. I remember, also, hearing, when a boy, the story of a June freshet on the Poultney River, in Vermont, caused by a succession of thunder- showers about its head waters. The rise in the lower part of the stream amounted to thirty or forty feet. The thing which fixed itself most deeply in my mind was that a milldam upon Hub-
�� � THE CINCINNATI ICE DAM. 197
bardton Creek, which was not affected by the showers, was carried up stream by the water which set back from the river. Thus it is easy to see that the glacial floods which poured into the Ohio from its northern tributaries would, during their continuance, produce slack water in its southern tributaries.
A more permanent class of dams is produced when a super- abundant amount of earthy debris is contributed by one tributary of a stream. It is thus that the Chippewa River, in Wisconsin, has brought down an excessive amount of sand and gravel into the Mississippi, where, owing to the gentler gradient and the slower current in the larger valley, a delta has been pushed out across the Mississippi, ponding back the water so as to form the enlargement known as Lake Pepin. Dr. George M. Dawson de- scribes a more striking instance in one of the principal tributaries of the Fraser in British Columbia, where Dead Man's Creek joins the Thompson. Here a sufficient amount of gravel has been brought down to silt up the main stream to a depth of four hun- dred and fifty feet, forming Kamloop's Lake, which is eighteen miles long and two miles wide. It is thus that the glacial silts coming into the channel of the Ohio from its northern tributaries have assisted the Cincinnati ice dam in the work that was laid upon it.
On the other hand, it is clear that the Cincinnati ice dam must in turn have assisted greatly in the silting process already re- ferred to ; for, as far up the Ohio as slack water was produced by the obstruction at Cincinnati, the deposition of the finer silt must have been greatly facilitated by it. At the same time the deposition of gravel near the mouth of the streams joining the Ohio above Cincinnati, and the obstruction offered by the rock strata, which have since been worn out in the new channel below Cincinnati, combined to relieve the ice gorge there from the sup- posed incredible hydraulic pressure which some have thought to be fatal to the hypothesis.
In conclusion, it may be said with a fair degree of confidence that the theory of the Cincinnati ice dam still "holds water," though the obstruction itself disappeared many thousand years ago. One may readily admit that some things were at first at- tributed to the dam which were the result of other causes. But fresh considerations have given increased interest to the theory, so that altogether it remains one of the most striking of all the episodes connected with geologic history, and it is all the more dramatic because of its probable connection with human history. There is, therefore, ample justification for the language of Prof. Claypole, in his paper upon the subject, read before the Geological Society of Edinburgh in 1887, and printed in the Transactions of that year.
�� � 198 THE POPULAR SCIENCE MONTHLY.
Having described the desolation sometimes produced in Switz- erland by the bursting of glacial lakes, he remarks that to a still greater extent the " period of conflict between the ice and the river must have been a terrible time for the lower Ohio Valley and its inhabitants. At times the river was dry, and at others bank-full and overflowing. The frost of winter, by lessening the supply, and the ice-tongue by forming a dam, combined to hold back the water. The sun of summer, by melting the dam, and the pressure of the accumulated water, by bursting it, combined to let off all at once the whole of the retained store. Terrible floods of water and ice, laden with stones, gravel, and sand, must have poured down the river and have swept away everything in their path trees, animals, and man, if present.
" How many years or ages this conflict between the lake and the dam continued it is quite impossible to say, but the quantity of wreckage found in the valley of the lower Ohio, and even in that of the Mississippi, below their point of junction, is sufficient to convince us that it was no short time. ' The Age of Great Floods ' formed a striking episode in the story of ' The Retreat of the Ice.' Long afterward must the valley have borne the marks of these disastrous torrents, far surpassing in intensity anything now known on the earth. The great flood of 1884, when the ice-laden water slowly rose seventy-one feet above low- water mark, will long be remembered by Cincinnati and its inhabitants. But that flood, terrible as it was, sinks into insignificance beside the furious torrent caused by the sudden even though partial breach of an ice dam hundreds of feet in height, and the discharge of a body of water held behind it, and forming a lake of twenty thousand square miles in extent.
"To the human dwellers in the Ohio Valley for we have rea- son to believe that the valley was in that day tenanted by man these floods must have proved disastrous in the extreme. It is scarcely likely that they were often forecast. The whole popula- tion of the bottom lands must have been repeatedly swept away ; and it is far from being unlikely that in these and other similar catastrophes in different parts of the world, which characterized certain stages in the Glacial era, will be found the far-off basis on which rest those traditions of a flood that are found among all savage nations, especially in the north temperate zone."
��Mr. W. H. Dines, an English meteorologist, is inclined to believe, from ob- servations and experiments made with his new anemometer, that a gust sel- dom maintains its full power for more than one or two seconds; and that the extreme velocity occurs in lines which are roughly parallel to the direction of the wind.