Page:Popular Science Monthly Volume 28.djvu/567

Rh Mr. Eads bad not commenced the jetties before he turned his attention to the improvement of eleven hundred miles of the Mississippi throughout its alluvial basin by the jetty system. On March 15, 1874, in a letter to the Hon. William Windom, chairman of the Senate Committee on Transportation Routes to the Seaboard, the first outline of this novel plan was suggested.

In his review of the United States Levee Commission, February 19, 1876, Mr. Eads said:

"By the under-charge theory of the Delta Survey Report, caving banks are attributed to the direct action of the current against them, by which strata of sand underlying those of clay are supposed to be washed out. This is not eorrectcorrect [sic]. If the water be charged with sediment to its normal supporting capacity, it can not take up more unless the rate of current be increased. Caving banks are caused wholly by the alternations in the velocity of the current. Alternations are inseparable from a curved channel, because the current in the bend is usually more rapid than on the point; but, if the channel be nearly uniform in width, the caving caused by the curves will be very trifling. And, in proof of this, many abrupt bends exist in the lower part of the river where the whole force of the current has set for years directly against them without any important caving of the banks. The bend at Fort St. Philip is a notable instance, the great difference in the width of the flood-channel constituting the real cause of the destruction and caving of the banks. This tends to great irregularities in the slope of the flood-line, and, consequently, great changes in current velocity by which a scouring and depositing action are alternately brought into very active operation. The whole of the river below the Red River proves this; caving banks are much less frequent there than above, because the flood width of the river is far more uniform. A correction of the high-water channel, by reducing it to an approximate uniformity of width, would give uniformity to its slope and current, almost entirely preventing the caving of its banks, and through its present shallows, which now constitute the resting-places for its snags, there would be a navigable depth, in low water, equal to that which now exists in its bends. By such correction the flood-slope can be permanently lowered, and in this way the entire alluvial basin, from Vicksburg to Cairo, can be lifted, as it were, above all overflow, and levees in that part of the river rendered useless. There can be no question of this fact, and it is well for those most deeply interested to ponder it carefully before rejecting it; for the increased value given to the territory thus reclaimed can scarcely be estimated.

Two years later, in a review of Humphreys and Abbott's "Report on the Physics and Hydraulics of the Mississippi River," published in Van Nostrand's "Engineering Magazine," Mr. Eads elaborated this plan, and combated the declaration that the bed of the river is formed of blue clay and will not erode unless very slowly under the effect of