144 
Proceedings of Boyal Society of Edinburgh. [sess. 
the various possible periods of oscillation of the liquid and the 
positions of the corresponding nodal lines with reference to any 
fixed line ; also to determine for each curve the effect of altering 
the maximum depth of the liquid. 
The first experimental method to be devised was a means 
to excite the various seiches. Obviously oscillatory motion 
necessitates regularly-timed impulses. A method of imparting 
such impulses to the liquid by means of a weighted spiral spring 
f/G:2T. 
AT: 
AT: 
Wafe r L ine. 
r. 
n 
G Wire-gauze. FFFF Wood frame of pendulum 
KK Knife-edge supports. supporting wire-gauze. 
W Weight of pendulum. T Trough. 
SS Supports of Pendulum. 
is described on p. 612 of the paper by Professor Chrystal referred 
to above. This is not in all cases practicable. Another method 
that suggested itself was to make use of a pendulum with 
a sufficiently heavy bob to give it motive power. To this was 
attached a frame-work of wire gauze, which, besides being rigid, 
had the additional advantage of allowing the water to pass freely 
through it (figs. 2, 3). 
