Models illustrating some Properties of the dither. 441 
ae \? & 
a ) + =). If we 
were to build up a tridimensional model by simply putting 
together three such systems of wheels in three rectangular 
planes, the kinetic energy of an element of the model would 
be proportional to 
bouring wheels, will be proportional to (2 
a Pe, 
but its potential energy would be simply 
dep ae)’, dal, dnp | del | dep 
ea oe, 
du| ° dy|  dz| ' da| ° dy| dz 
instead of 
eae as) Gea) 
dy dz dz dv dy 
which is what it should be if it is to represent the ether. 
The electrostatic and electrokinetic energies of an element 
of the ether may be expressed in this form by assuming 
£,,and such that their velocities £, , and ¢ are a, B, and y, 
the components of the magnetic force at the element. Now 
simple band-gearing will not enable us to arrange that no 
straining shall result, when, for instance, =p but this 
may be accomplished by the following arrangement :—Hach 
element of the ether is to be represented by a cube, on each 
edge of which there is a paddle-wheel. Thus on any face of 
the cube there will be four paddle-wheels. Now, if any oppo- 
site pair of paddle-wheels on a face rotate by different amounts, 
they will tend to pump any liquid in which the whole element 
is immersed into or out of the cube, and if the sides of the 
cube be elastic there will be a stress which will tend to stop 
this differential rotation of the wheels. If, however, the other 
pair also rotate by different amounts they may undo what the 
first pair do ; and thus the stress will depend on the difference 
between the differential rotations of these opposite pairs of 
alee dn d 
wheeis, 7. ¢. on ae 
In order that these four wheels may not similarly work 
with any other wheel in the cube it is necessary to place 
diaphragms, cutting the cube into six cells, each a pyramid 
standing on a face of the cube. These must be so made that 
liquid may not be able to pass from one cell to another through 
the diaphragm, nor beside the paddle-wheels. In order 
actually to effect this, the floats on the paddle-wheels would 
have to be drawn down while passing the diaphragm (of 
