heats it with its contained water, we have not only the heated water but also an electrical current; it is evident, therefore, that we should be able to heat the water more when the wire between the two vessels is cut, than when there is a metallic circuit between them, for a part of the energy of the falling weight has become converted into an electrical current. At the terminals of the cut wires there is a difference of electrical potential created for an instant, which, however, instantly disappears. What is the equivalent of the disappearance of this difference of potential? Is it not in the closed circuits through the masses of the metals, a part of which, it is true, becomes sensible heat, but another portion may become latent heat or do internal work among the molecules?
Moreover, is it not reasonable to suppose that certain anomalies which we now find in the determinations of specific heats of complicated aggregation of molecules are due to our failure to estimate the electrical equivalent of the movements and interchanges of the molecules? Let us take, again, the case of friction between two pieces of wood: is it not possible that the friction is the electrical attraction which results from the endeavor to move the adjoining particles of wood in the two pieces asunder? Let us remember, in our endeavor to connect the phenomenon of superficial energy with electrical manifestations, that the friction between two surfaces is modified by keeping these surfaces at a difference of electrical potential. In Edison's motophone, by means of which the voice of one speaking in New York could be made audible to this audience, we see this exemplified in a very striking manner. A platinum point connected with one pole of a battery rubs upon a revolving cylinder of chalk, which is simply moistened with water and is connected with the opposite pole of the battery. The friction between the two is modified in unison with the changes in electrical potential of the battery; and a diaphragm in connection with the platinum point responds to these changes in the friction, and therefore to a transmitter placed anywhere in the electrical circuit.
My own studies have been chiefly in the direction of thermo-electricity, and in the subject of the electrical aspect of what we call superficial energy. I think there is a great field here—in which a large crop of negative results can be reaped—but these negative results I can not regard entirely as thistles. I have tried the following experiment, on the hypothesis that an electrical difference of potential in changing the relations of molecules might modify the heat that is radiated from a surface. I have endeavored to discover whether an electrical current first cools a conductor before it heats it, as we might expect if the molecules being restrained in any way could not radiate as much energy into space as they could under the same difference of temperature, when not submitted to the action of an electrical difference of potential. I have reaped only a thistle so far from this investigation, but I shall
