SSLlSrriff] and Microscojpic Physics. 17 
deed, he contrived one form of this experiment for the purpose of 
illustrating my remarks in this paper. 
It consists of a strip of the metal palladium in water. When 
contact is made with a small galvanic battery these strips of metal 
will roll themselves up into spiral coils. Some will vibrate, some will 
actually move forward with a motion closely resembling that of a 
common earth-worm. On the connection with the poles of the 
battery being reversed, all the movements will take place in a 
contrary direction. These strange movements are caused by the 
metallic palladium absorbing the hydrogen which would otherwise 
be given off by the decomposition of the water. This hydrogen is 
expelled when the poles of the battery are reversed, or it unites with 
the oxygen which is now produced, and together they form water. 
This arrangement can also be made automatic. Yet this palla- 
dium will in time lose the property of expanding and contracting 
on being connected with the battery, because its molecules have 
undergone a great change in their arrangement, not, I presume, 
because the palladium has lost its vital force. 
Fortunately we are not in doubt as to what change occurs, for 
Mr. Koberts, after repeatedly charging a palladium wire with 600 
times its own volume of hydrogen, and then expelling it, examined 
the wire with a microscope and found it torn and rent asunder. 
This motion is due to physical causes over which we have com- 
plete control; but, apart from such cases as this, we have good 
reasons for beheving that all forces are modes of motion. 
If we take a powerful galvanic battery, we find the chemical 
action changed into, or producing electricity. Cause this electricity 
to pass through a wire and the wire will become hot ; let it pass 
through a smaller wire, that is, interpose a greater resistance to its 
passage, and the wire will become white hot and give out light. 
By allowing the heat to fall on a thermo-pile, we can again convert 
it into electricity. 
Light has long been considered as due to the rapid undulations 
of ether. Heat and electricity Prof. Tyndall and Mr. Brooke have 
taught us to regard as modes of motion. On this hypothesis the 
correlation of the physical forces becomes an exceedingly simple 
matter to understand. 
When we throw a spectrum on a screen, if we use a delicate 
thermometer, we find that the greatest heat exists beyond the 
visible rays of the red end of the spectrum. Dr. Tyndall has shown 
these heat rays may be separated from the light rays, and various 
substances may be set on fire by such rays brought to a focus by a 
lens, the substances becoming heated and hghted without contact 
with other matter in the dark, the effect being a result of invisible 
motion. This fact would probably be disposed of as inconceivable 
by anyone unacquainted with physics. 
VOL. II. c 
