ON WAVES. 453 
In order to make these observations the foundation of any 
conclusions, it will be necessary to observe that it is scarcely 
possible to determine whether the wave which brings flood tide 
to the lower station be the same with that which afterwards 
brings flood tide to the higher station; on the other hand it 
seems more likely that the wave which passed the lower station 
was diffused over the intermediate space in the channel, and 
was overtaken by a subsequent part of the tide, which had not 
reached the lower station till a considerable time after the first 
wave had passed it. This is not a conjecture, but has frequently 
been observed in similar cases where the first wave being be- 
come diffused in the channel ceased to pass onwards and was 
overtaken by a subsequent wave. The result obtained in the 
case of waves I., II., and III. of flood tide is consistent with 
this view, and shows that in these cases the progress of flood 
tide is slower than the velocity due by gravity to the wave of 
the fluid. It is also consistent with the experiments of the 
previous part of this paper, that a breaking wave or bore, as 
this was, has a slower velocity than one which does not break. 
Waves IV., V., and VI., the waves of high water, have almost 
exactly the velocities of great waves of translation of the fluid. 
It will be seen at once by examining the transverse sections of 
the river, that wave IV. must suffer great retardation from the 
‘circumstance that its progress is continually intercepted by the 
groins to which it is almost exactly equal in height, while waves 
V. and VI. rise above them and accordingly approximate more 
closely to the velocity due to the depth. The form of these 
waves and their antecedent bores are given in Plate VI. figs. 1 
and 2. and the observations from which they are deduced are 
given in the following table. 
