200 ^V J MCGEE OUTLINES OF HYDROLOGY 



(expressed in terms of declivity or slope) and friction; and it may be said 

 to be tlie primary function of moving water to modify and eventually to 

 regulate the declivity and other factors in such manner as to develop the 

 harmonic lineaments of the earth face — ^to produce dendritic river sys- 

 tems and paraboloid grades adjusted to the internal harmony of water 

 . movement, sculpturing square miles of surface and displacing and re- 

 placing cubic miles of earth matter in the course of its work. 



REFLEX FUNCTJOSS OF WATER WORK 



The running water is itself modified by its own work : The matter car- 

 ried in solution (ordinarily small in amount) adds to its weight, and 

 generally to its volume and specific gravity, while the matter carried in 

 suspension commonly adds to weight and volume and also to viscosity; 

 and generally both modifications are within limits cumulative — for ex- 

 ample, the presence of matter in solution may add to the solvency for 

 other substances, and the presence of suspended matter adds to the effi- 

 ciency in corrasion if not to the capacity for load. 



Still more responsive to the work of the stream is the matter carried in 

 saltation; this matter is itself the chief agent of corrasion; with in- 

 creased volume or declivitj^, both its amount and vigor of movement 

 increase cumulatively in a geometric ratio; with diminishing velocity 

 or volume of the stream, the saltatory matter and its activity decline 

 geometrically until the stream, as it were, lays aside its tools (virtually 

 disposing of them as building material) and turns from vigorous and 

 chiefly mechanical to sluggish and largely chemical work. "^Tiile in 

 movement the saltatory rock matter adds to the volume and weight and 

 specific gravity and measurably to the viscosity of the flowing medium; 

 and since it is taken up and laid down at what is frequently paraphrased 

 as the caprice (or will) of the stream — actually its responsion to gravity, 

 friction, etcetera — it, like the matter in solution and suspension, intro- 

 duces an autonomous factor in the behavior of the stream and thereby 

 transfers the moving medium from the domain of the hydrodjTiamic 

 into what may be considered the domain of the hydrokinetic — that is, 

 from the merely passive to the partly self -active. 



So not only in the large way noted above does the hydrosphere assume 

 an autonomous or kinetic property' in regulating temperature and other 

 planetary conditions, ])ut in a special way, through what may be ex- 

 pressed (hardly paraphrased) as exercise of function, that division of 

 the hydrosphere found in running water displays at least an approach 

 toward autonomy and kinesis. As a part of the hydrosphere, the stream 



