354 WAVES OF THE SEA 



train of waves behind. This suggests that by drip- 

 ping oil out behind a vessel one might succeed 

 in showing the detailed pattern of the ship-waves 

 even when there is a slight breeze on a lake. I 

 had to do the double journey before I could get 

 my camera, and the photographs were taken on 

 the second journey down the lake. 



The effect of interference between the diverg- 

 ing waves from bow and stern was noticeable in 

 the series of breakers which came in upon the 

 beaches near Gunten after the passage of a steamer 

 on the Thunersee. The surf was found to be inter- 

 rupted by lulls during which the breakers were 

 much smaller. 



When observing from the ship, or from a posi- 

 tion near her, the strong curvature of the fronts 

 of the individual diverging waves is a marked 

 feature of the wave -track. When, however, I went 

 to a considerable height upon the hillsides in order 

 to obtain a bird's-eye view of the wave-track I 

 often passed the distance where the waves were 

 individually distinct or even discernible. Curved 

 lines then ceased to be seen and were entirely re- 

 placed by lines which were of rigid straightness 

 whenever the ship was running a straight course. 

 When we are near, the case is similar to that de- 

 scribed in the phrase " one cannot see the wood 



