<9.V SHIP WA VES. 



491 



length, but I may tell you that it is as the square of 

 the velocity : the wave-length is four times as great 

 for 1 8 as for 9 knots. Look now at the pattern 

 of the waves in Figs. 9, (48 above), and 10, Plate 

 82. Look at the echelon waves and the thwart- 

 ship waves. Mr. Froude had not worked out the 

 theory that has given the curvature of the trans- 

 verse ridge exactly ; but he drew the waves from 

 general observation, and it is wonderful to see 

 how nearly they agree with the theoretical curves, 

 Fig s - 9> (4-8 above), and the model, Fig. 10. 



VELOCITY AND LENGTH OF WAVES. 



That is a most interesting series of diagrams in 



