Mr GREEN, ON THE MOTION OF WAVES IN CANALS. 



93 





Mr Russel gives V -§— as the velocity, but at the same time 



remarks, that in consequence of the attraction of the sides of the canal 

 fixing a portion of the fluid in its lower angle, we ought in employing 

 any formula to calculate for an effective depth in place of the real one, 

 p. 442. Instead of adopting this method, let us compare the formula 

 (D) given by the common Theory of Fluid Motion, with Mr Russel's 

 experiments. And as in our theory we have considered those waves 

 only in which the elevation above the surface of equilibrium is very 

 small compared with the depth c, it will be necessary to select those 

 waves in which this condition is nearly satisfied. I have therefore taken 

 from the Table, p. 443, all the waves in which 



and have supposed g = 32i 



Y 

 feet: the results are given below. 



A more perfect agreement with theory than this could scarcely be 



expected. Had the formula \Z~i~ = v keen usec *' tne errors w °uld 

 have been much greater. 



