Canon Moseley on the steady Flow of a Liquid. 51 



oy experiment. 



And comparing experiment 8 and 3, Series 2, 



Z>=:1-812, c, = -2095, C2 = -1997; 



by theory_, 

 by experiment, 



^=2-6081; 

 %' =2-68. 



Current -lines and Cmrent-sm faces. 



In fig. 3^ A B represents a line supposed to be drawn in a ho- 

 rizontal plane through the point of maximum velocity at right 

 angles to the current experimented on, MM. Darcy and Bazin's 

 Series 53, and represented in fig. 1. The divisions along it, 

 through which are drawn lines parallel to the sides of the chan- 

 nel, represent distances of 0*11 metre each; the figures repre- 

 sent the velocities of the current at those several points as deter- 

 mined by experiment. The velocity at each point is set ofi" on 

 the line passing through it in the direction of the current, twelve 

 successive times ; and then the points so set off are supposed to be 

 joined across the current so as to form a series of polygons, 

 which, if the points of division in A B had been infinitely near 

 to one another, would have been curves. If a line of small 

 floating bodies, such as particles of camphor, be supposed at any 

 instant to be dropped on the surface of the current along the 

 line A B, then at the end of 1" these particles carried along hy 

 the water will have arranged themselves in the curve next to 

 A B, and at the end of 2" in the curve next beyond thatj and so 

 on, until at the expiration of 12'' they will form the curve acb. 



These current-lines are those in which particles of liquid 

 starting at the same given instant from the same line mea- 

 sured across the current will be at the end of the same given 

 time. If instead of a powder being dropped upon the surface 

 along the line A B, a wavelet had instantaneously been created 

 along that line, that wavelet would have taken the form of the 

 current-line, and the ripple would have been created which is 

 seen in currents. It is not necessary that such a wave should 

 be called into existence right across the current. If created 

 by some obstruction in the side of the channel, it would still 

 be absorbed into the portion of the current-line nearest it and 

 constitute an imperfect ripple. 



E2 



