AND OTHER WATER WAVES 313 



for any one day. The figures show a less simple 

 relationship, the period increasing somewhat slowly 

 at first, although towards the end of the course the 

 increase is more nearly proportional to distance 

 run. 



It will be seen from the tables that the rate of 

 increase of period is nearly the same on different 

 days when the depths differed by moderate 

 amounts. In order to make a thoroughly satis- 

 factory examination of such relationship it would 

 be necessary to know, not only the distance run 

 by the wave relatively to the bank, but also the 

 distance travelled through the water, which was 

 not determined on every occasion. 



The following figures show the degree of irregu- 

 larity in the intervals between successive wave- 

 crests at the outfall. This measurement, made 

 with a stop-watch, is very easily taken, and is free 

 from the uncertainties which attended the measure- 

 ment of depth, and, to some extent, of the velocity 

 of current. 



The intervals between Successive Wave-crests at Outfall of the 

 Griinnbach. In Seconds. 



5, 3, 4, 8, 4, 7, 4, 4, 2, i, 



5, 4, 5, 6, 4, 5, 3, 3, 4, i, 



6, 3> 4) 2, 4, 4) 3, if 7, 2, 



7, 9, 2, 9, 8, i, 10, i, 5, 6, 

 i, 4, 9> J > 6 , *i 2 > 6 > 7, 4, 



