stitute for this part; then its electroscopic force, measured in the way described, will, when it happens to be different at the various places, make known the relative difference with regard to electricity between these places.
The intention of the preceding explanations is to give a simple and determinate signification to the expression "electroscopic force"; it does not come within the limits of our plan to take notice either of the greater or less practicability of this process, nor to compare inter se the various possible modes of proceeding for the determination of the electroscopic force.
2. We perceive that the electroscopic force moves from one place to another, and from one body to another, so that it does not merely vary at different places at the same time, but also at a single place at different times. In order to determine in what manner the electroscopic force is dependent upon the time when it is perceived, and on the place where it is elicited, we must set out from the fundamental laws to which the exchange of electroscopic force occurring between the elements of a body is subject.
These fundamental laws are of two kinds, either borrowed from experiment, or, where this is wanting, assumed hypothetically. The admissibility of the former is beyond all doubt, and the justness of the latter is distinctly evident from the coincidence of the results deduced from calculation with those which actually occur; for since the phænomenon with all its modifications is expressed in the most determinate manner by calculation, it follows, since no new uncertainties arise and increase the earlier ones during the process, that an equally perfect observation of nature must in a decisive manner either confirm or refute its statements. This in fact is the chief merit of mathematical analysis, that it calls forth, by its never-vacillating expressions, a generality of ideas, which continually excites to renewed experiments, and thus leads to a more profound knowledge of nature. Every theory of a class of natural phænomena founded upon facts, which will not admit of analytical investigation in the form of its exposition, is imperfect; and no reliance is to be placed upon a theory developed in ever so strict a form, which is not confirmed to a sufficient extent by observation. So long, therefore as not even one portion of the effects of a natural force has been observed with the greatest accuracy in all its gradations, the calculation employed in its investigation only treads
