1905 - 6 .] The Hydrodynamical Theory of Seiches. 155 
and lengthen considerably in period. These irregular oscillations 
gave quite inconsistent results, which were greater than those 
obtained when the oscillations were regular. 
The binodal seiche in the same case presented less difficulty, 
but could not be increased in amplitude beyond a very limited 
amount. This latter was also more persistent than the uninodal, 
which died out very rapidly when left to itself. In the case of 
the concave parabola and the quartic curve, it was possible to 
obtain easily even seiches of a high nodality (in the case of the 
quartic curve as high as the seventh), and these could be forced to 
a considerable amplitude, showing also a remarkable persistency, 
particularly as regards the latter curve. 
(2) When a vertical barrier was inserted at a ventral segment, 
the seiche motion still continued to be transmitted from one 
portion of the liquid to the other, even when the passage between 
these two portions was considerably constricted. 
(3) Rhythmic movements are generally persistent as contrasted 
with random displacements which have no periodic connection 
with the form of the vessel in which they take place. In this 
connection the movement of the water in a rectangular trough 
calls for remark. If the end of the vessel be raised and then 
lowered, a group of high w r aves or a bore passes along the surface 
and is reflected from the end, when it returns along its former 
path. After the motion has somewhat subsided, the movement 
of the water begins to assume a certain symmetry. 
Gradually the smaller waves die out on the slopes of the larger, 
until two waves are left which move backwards and forwards 
