1905 - 6 .] The Hydrodynamical Theory of Seiches. 
153 
These give the ratios 
T 
fir 1 ' 84 
as contrasted with 
T 
e- ! “ 
T 
Fp — 1 '79 
1 o 
for the calculated and 
T 
±1=1-81 
do 
^1 = 2-54 
t 3 
T 1 = o. 
2-43 
for the observed periods of the actual loch. 
The experiments whose results are tabulated on pages 146-149 
are by no means exhaustive, nor was it the aim of the writers 
to make them so. The purpose in view was rather to furnish 
sufficient experimental data to supply material for a critical 
comparison with theoretical calculations. 
The respective movements of the water particles at a ventral 
segment, and at a node of a seiche, may be experimentally demon- 
strated by means of a float whose motion is magnified by being 
transmitted to a pointer in a manner best explained by the 
accompanying illustration. When the float is placed at a ventral 
segment, the end of the pointer moves through a range of several 
inches in unison with the oscillating water. When the float is 
placed at a node the vertical movement of the end of the pointer, 
if not entirely eliminated, is reduced to a minimum. 
If we imagine one seiche superposed on another it will be seen 
that the motion due to the one can be recorded independently 
of the motion of the other. For, if a uninodal seiche is in 
existence along with a binodal seiche, a float on the uninodal line 
will have no vertical motion from the uninodal seiche, but only 
from the binodal, and on a binodal line will have vertical 
motion due to the action of the uninodal seiche alone. 
This may be experimentally shown by raising the end of the 
vessel when the pendulum (fig. 3) is keeping up a binodal 
seiche, thus superposing on the latter, a uninodal seiche. At 
the binode and uninode the pointer (fig. 5) moves in the uninodal 
and binodal periods respectively. In all other positions its motion 
is a combination of the two motions. 
