C. pea new form of Wave apparatus. 385 
tions also that are at the same time taking ae below the 
surface, in the whole mass of liquid ‘affected. This complete- 
ness of. illustration is due to the circumstance, that in the ap- 
paratus, the elementary motions: are the same, essentially, as 
in actual waves; hence, the leading points, geometrical and 
dynamical, of the theory of waves, are presented naturally, 
and in their true relations. 
he construction of the apparatus will be aif understood 
from a brief description, and the accompanying cu 
In front of a oe surface are two series of revolving arms 
r cranks, the length of the lower ones = half that of the 
upper. Two elastic wires connect the ¢ -pins of each se- 
ries ; upright wires also connect each pair of ge and pass 
Cone through a Soy into the base. The cranks paar sigs revolve 
ative re pnt of the cranks of — higiehctad series is eg 
their axes is of a whole wave — Thus, in the apparatus. 
the wave length is upposed to be divided Jen a sie equal 
parts, and hei ens a ties difference betw: re 
Am. Jour. Scor.—Ssconp Series, Vou. ee snare dp 
