324 WAVES OF THE SEA 



pool When there was very little water, the 

 formation of the waves appeared to be capricious, 

 a long interval occurring, during which the stream 

 flowed steadily, to be succeeded by a fairly regular 

 series of waves. On the small conduit of St. 

 Maurice, 1 already referred to, this capriciousness 

 was still more marked, and more obviously de- 

 pended upon some slight variations in the strength 

 of the stream, caused one knows not how. It is 

 evident that in this case we have something rather 

 like the roll-waves of the Tees on a minute scale. 



The average depth in the conduit of the 

 Guntenbach was difficult to determine on account 

 of the inequalities of the pavement, but 2 inches 

 was a usual amount. The speed of the current 

 was determined at 8.5 feet per second, and the 

 true speed of the wave at approximately 2.25 feet 

 per second. On one occasion the depth at crest 

 at outflow was estimated at 3.5 inches, and at the 

 trough 2 inches. 



On more than one occasion a thunderstorm filled 

 the conduit to a depth of from 5 inches to 9 inches, 

 and then there was absolutely no roll -wave or 



1 Average period of waves, 13-5 seconds. The conduit was 

 only 3 feet wide, and paved with blocks extending the whole 

 width, so that there were no longitudinal joints, which in the 

 Guntenbach tend to spoil the wave by making unequal depths in 

 cross-section. 



