Licence: Public Domain Mark
Credit: Therapeutic electricity and practical muscle testing. Source: Wellcome Collection.
Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)
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![Electrical Electricity and electrijication.—What is electricity ? Two theoiy. hundx'od and fifty years ago it was a viscous fluid ; to-day we are awaiting proof of some universal connecting medium, some subtle tenuous gether, that will explain electricity, magnetism, and light, perhaps chemical affinity and gravita- tion. It is only open to us to say that electricity is an invisible agent, unknown excepting by its effects. It is appa- rently indestructible and uniformly distributed. The text- books of half a century ago follow Franklin in his one fluid theory and Symner in his two fluid theory. Ac- cording to the former, electricity is a single imponderable fluid, the particles of which, although they mutually repel each other, attract all matter; and every substance has the capacity for containing a definite quantity of this fluid. When the normal quantity is present no ]3henomena are manifested; when there is less than the full quantity the body is charged negatively; with more than the quantity the body is charged positively. In other words, the pheno- mena of electrification depend upon a phis or minus of the fluid. The two fluid theory assumes that there are two kinds of electricity, and these are compared to fluids. They are self-repellent, but mutually attract. They both attract matter. In an unelectrified body they coexist in equal quantities and neutralise each other. The act of separating these fluids constitutes the phenomena of electrification. These fluids are distinguished as positive and negative, and by the signs plus and minus. Whatever it may be, electricity is certainly not a material fluid : it has no weight, and it is impossible to imagine a substance which is self-repellent. The fluid theory gave place to the view that electricity is a form of energy. Now energy, like matter, is inde- structible, and so apparently is electricity; but it is not true to say of any particular form of energy that it is indestructible. It is obvious that any form of energy as such can be created by being transformed from some other form or destroyed by](https://iiif.wellcomecollection.org/image/b21271860_0018.jp2/full/800%2C/0/default.jpg)
