1878.] Uniform Regime in Rivers and other Open Channels. 125 



from the bottom, or of water retarded by the influence of the river- 

 bed, we ought to expect the forward velocity to increase from the sur- 

 face to very nearly the bottom. The accelerative influence of gravity 

 due to the surface inclination, and more particularly due to the fall of 

 free-level experienced, as an accompaniment of that inclination, by the 

 water throughout the body of the current in its onward flow would 

 generate in every portion or particle of this water increase of velocity 

 for advance along its course ; because, in the absence of rushes of 

 deadened water from the bed, such as it appears do commonly intrude 

 into the body of the current, there would be no retardative influence to 

 counteract the gravitational accelerative influence ; since the mere 

 viscosity of the water unaided by transverse commingling is, I con- 

 sider, insignificantly small and quite ineffectual as a resisting influence 

 or means of transmitting resistance from the bed to any part of the 

 water in the body of the current out of close proximity to the bed. 

 But as this forward moving water is also descending towards the 

 bottom while it is gaining forward velocity, it follows that, in the cir- 

 cumstances of flow supposed, we ought to expect the forward velocity 

 to increase with descent from the surface to very nearly the bottom. It 

 is to be understood that the freedom supposed from upward rushes or 

 intrusions of deadened water will not be maintained in the water when 

 it arrives into proximity to the bottom. In approaching very near to 

 the bottom the water must begin to receive important resisting forces 

 communicated to it from the bottom through commingling of dead- 

 ened water, and by intense distortional actions with viscosity. 



It is also to be noticed in connexion with the case under con- 

 sideration that if, in one part of the width of the river, there is a pre- 

 vailing descent towards the bottom, there will be upward flows to 

 compensate for this in other parts of the width. Then obviously the 

 whole character of the action of the water will be very different in the 

 regions where ascent prevails from that in the regions where there is 

 a prevailing descent; and the distribution of forward velocities 

 throughout any vertical line in the one region will be quite different 

 from the distribution of forward velocities throughout any vertical 

 line in the other region. Local circumstances casually affecting the 

 flow in the way here described I think may perhaps account for some 

 of the apparent anomalies in respect to the distribution of velocities 

 through different parts of the depth from surface to bottom which 

 have been met with by various experimenters, and have been included 

 among the recognised causes of the perplexity and bewilderment with 

 which this branch of hydraulic science is pervaded. 



I wish next to draw attention to one of the results of observation 

 and experiment announced by Captain Cunningham in his book 

 already referred to ("Hydraulic Experiments at Roorkee"). In his 

 discussion of his experimental results on the flow of water in each of 



