R has a textbook entitled Modern Electricity: Science, History, Theory, and Practice. It was published in 1904. Here is the first paragraph:
The true nature of electricity has not yet been discovered. Many think it a quality, inherent in nearly all the substances, and accompanied by a peculiar movement or arrangement of the molecule. Some assume that the phenomona of electricity are due to a peculiar state of strain or tension in the ether which is present everywhere, even in and between the atoms of the most solid bodies. If the latter theory should be the true one, and if the atmosphere of the earth is surrounded by the same ether, it may be possible to establish these assumptions as facts. The most modern supposition regarding this matter, by Maxwell, is that light itself is founded on electricity, and the light waves are merely electro-magnetic waves [italics in the original]. The theory "that electricity is related to, or identical with, the luminiferous ether," has been accepted by the most prominent scientists.
Isn't that charming?