328 WAVES OF THE SEA 



caused a stationary wave, also caused progressive 

 waves. Close to Schloss Ralligen (between Gunten 

 and Merlingen) is a short and very steep conduit, 

 3 feet wide, with a pavement of ribbed form, each 

 rib extending quite across the conduit. The 

 distance from the summit of one rib to that of 

 the next is 6 inches, and the line of the crest of 

 the ribs is about 0.3 inches above the line of their 

 troughs. The depth of water covering the crests 

 of the ribs was 0.5 inch. The appearance of 

 the whole is that of a cascade with transverse 

 bars of white foaming water, situated at the 

 summit of each rib, these transverse bars showing 

 (as is usual in cascades and waterfalls of small 

 dimensions) a longitudinal striping, so that the 

 form of the standing waves caused by each 

 rib is that of a comb, the back of the comb 

 representing the principal transverse line of white 

 water, and the teeth the smaller longitudinal lines 

 of white water. This, with a slight flicker, was all 

 that I saw in 1904. But in 1905, being now aware 

 how stationary objects fix the eye so that it cannot 

 distinctly see moving things, 1 I tried the expedient, 



1 Conversely when moving bodies are many and conspicious 

 the attention is distracted from stationary objects. A good 

 example of this may be obtained by visiting the vicinity of the 

 Mansion House in the City of London early on a Sunday 

 morning. Those who think that they are familiar with the sur- 



