Page:Popular Science Monthly Volume 45.djvu/212

198 Having described the desolation sometimes produced in Switzerland 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 reason 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 population 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."

an English meteorologist, is inclined to believe, from observations and experiments made with his new anemometer, that a gust seldom 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.