Sixteenth Annual Meeting. 133 



DISCHARGE. 

 1 have not seen the Arkansas where it leaves the State, but from my information and 

 knowledge of the stream, I estimate an average width of 840 feet, a depth of 1 j feet for 

 ten months in the year, and a velocity of 3^ miles per hour. Adopting this estimate, we 

 find that L33 billion cubic feet of water would be discharged from the State, on an aver- 

 age, in the course of a year. Of this amount, 72 billion cubic feet is carried into the 

 State from Colorado, leaving 01 billions to be collected in the State. The Kaw is not 

 quite so wide as the Arkansas, but is very much deeper, and flows with about the same 

 velocity ; and, unlike the Arkansas, the bed is not filled with quicksand. Besides, the 

 Kaw is never dry, as is the Arkansas, but flows all the year round. Yet I have no re- 

 liable data as to its average width and depth at its mouth. But calculating from the 

 annual precipitation and evaporation, I find that the Kaw should discharge 201 billion 

 cubic feet in a year, of which 70 billions come down from Colorado and Nebraska, leaving 

 130 billions to be gathered from the State. Similar calculation makes all other streams 

 carry off 134 billion cubic feet, entirely from Kansas. 



LOAD. 



The amount of earth carried by a stream is in proportion to the square of the pitch 

 or slope of surface of the earth multiplied by the excess of rainfall over evaporation and 

 seepage, and divided by the comparative solidity of rocks or tenacity of the soil, or in 

 other words, multiplied by the comparative friability and solubility of the earth and 

 rocks. This omits one important factor — time, because of the difficulty and uncertainty 

 of applying it. It is well known, for instance, that in a rainfall of three inches, dis- 

 tributed over three days and nights, the excess of rainfall would scarcely swell the 

 streams, whereas a rainfall of three inches, precipitated in an hour, would carry torrents 

 of muddy water and sand into the rivers. To put this formula into algebraic form it 

 would appear thus : 



1 = 0*- f or 1 = I? 2 



1 & l S 



In which I represents the load of earth carried by the water; r is the excess of rainfall; 

 p is the pitch of surface of the land; /is the comparative friability and solubility of the 

 earth and rocks; s is the solidity or tenacity, and t is the time from the beginning of a 

 rain to the end of it. However, this last factor (t) may be omitted, since it is only the 

 excess of rainfall over evaporation and seepage which is considered. The term seepage, 

 as used here, applies to that water which percolates through the earth deep enough to 

 pass ofl' in springs or subterranean streams, or lies quiet in the earth, and not to that 

 water which soaks into the earth and is afterwards taken up by plants, or otherwise used 

 or evaporated. 



Repeated observations show that the waters of the Arkansas carry about one five- 

 hundred-and-twenty-fifth of their bulk of earthy matter in suspension. A foot depth of 

 water dipped from the Arkansas will, when settled, contain a deposit of nearly one-for- 

 tieth of an inch of soil. The amount in solution is undetermined as yet; but for the 

 purposes of this article, may be figured at one-twentieth of the above amount, 

 or enough to say the Arkansas carries one cubic foot of solid matter for every five 

 hundred of water. The Kaw carries out one foot of solid matter for every six hun- 

 dred and twenty -five cubic feet of water. The other streams of the State are estimated 

 to carry off one foot of solid matter for every twelve hundred and fifty cubic feet of 

 water. 



Knowing, then, by experiment and deduction, the amount of water carried off by the 

 different streams, and the comparative amount of solid matter contained therein, it is 

 easy to arrive at the gross amount of earth removed from the State by its rivers in a 

 year, thus: The Arkansas carries out 306,960 cubic feet of earth per hour, and in ten 



