usually makes substances--metals in particular--electro-positive.
These statements are also consistent with the view that the elementary
substances lose a portion of their molecular activity when they unite
to form acids or salts, and that electrolytes therefore have usually a
less degree of molecular motion than the metals of which they are
partly composed.

The current from a thermo-couple of metal and liquid, therefore, may
be viewed as the united result of difference of molecular motion,
first, of the two junctions, and second, of the two heated (or cooled)
substances; and in all cases, both of thermo- and chemico-electric
action, the immediate true cause of the current is the original
molecular vibrations of the substances, while contact is only a static
permitting condition. Also that while in the case of thermo-electric
action the sustaining cause is molecular motion, supplied by an
external source of heat, in the case of chemico-electric action it is
the motion lost by the metal and liquid when chemically uniting
together. The direction of the current in thermo-electric cases
appears to depend upon which of the two substances composing a
junction increases in molecular activity the fastest by rise of
temperature, or decreases the most rapidly by cooling.

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AIR REFRIGERATING MACHINE.