PREFACE.

The internal relations of the different branches of the science which we have to study are more numerous and complex than those of any other science developed until now. Its external relations—on the one hand to dynamics The branch of mechanics concerned with the motion of bodies under the action of forces., and on the other to heat, light, chemical action, and the constitution of bodies—seem to indicate the special importance of electrical science as an aid to the interpretation of nature.

It appears to me, therefore, that the study of electromagnetism in all its extent has now become of the first importance as a means of promoting the progress of science.

The mathematical laws of the different classes of phenomena have been, to a great extent, satisfactorily determined.

The connections between the different classes of phenomena have also been investigated, and the probability of the rigorous exactness of the experimental laws has been greatly strengthened by a more extended knowledge of their relations to each other.

Finally, some progress has been made in the reduction of electromagnetism to a dynamical science, by showing that no electromagnetic phenomenon contradicts the supposition that it depends on purely dynamical action.

What has been done so far, however, has by no means exhausted the field of electrical research. It has rather opened up that field by pointing out subjects of inquiry and furnishing us with the means of investigation.

It is hardly necessary to enlarge upon the beneficial...