54 Kansas Academy of Science. 



by the chemical action of the atmosphere, in part by the mechan- 

 ical action of the flowing water. It matters not what the agencies 

 are in detail, the point is that it cuts its channel deeper. This 

 deepening of the channel will be continued until by and by a con- 

 dition will be reached which prevents the deepening process being 

 carried any further until general environments are changed. To 

 give all the details substantiating this would require too great a 

 time, but they are connected principally with the law governing 

 the carrying power of flowing water. The carrying capacity of 

 moving water varies as the sixth power of the velocity. Suppose, 

 for instance, we have a stream with its water moving one mile an 

 hour, and a second stream with its water moving two miles an 

 hour. The carrying capacity of the water in the second stream 

 will be sixty-four times as great as the water in the first stream. 

 It is difficult for one to believe that this statement is true, and yet 

 it is true both in theory and in practice, and has been incorporated 

 in our standard text- books for twenty-five years or more. 



Our stream under consideration during ordinary times will have 

 but a small amount of water in it, and that will move at a slow 

 pace, and will have but little carrying capacity. Its work in deep- 

 ening the channel will consist principally in the dissolving power 

 of the water. But when the heavy rains come and ten, twenty, 

 and a hundred times the amount of water is poured into the chan- 

 nel the velocity of the moving water is greatly increased, and the 

 carrying power correspondingly increased according to the ratio 

 above named. The energy of this moving water will be devoted 

 principally to cutting its channel deeper, until the water has all 

 the load it can carry. In order to deepen its channel more, there- 

 fore, it must be given a greater velocity, or in some way it must 

 get rid of some of its load. 



Suppose now that at some place along the channel the velocity 

 should be checked, never so little possibly. With a decrease in 

 velocity the carrying power will be decreased sixty-four times as 

 much. If the water was loaded to its limit a part of that load will 

 be deposited the very instant a perceptible checking of the velocity 

 is brought about. At that instant, therefore, the water ceases to 

 cut its channel deeper and the reverse process is begun — that of fill- 

 ing up the channel. Usually the decrease in velocity is at or near 

 the mouth of the stream, so that the filling up process begins at 

 the mouth. It is common, therefore, to find a stream which is still 

 cutting its channel deeper in its upper parts and the same stream 

 filling up its channel in the lower part of its course. 



