Introduction to the treatment of disease by galvanism / by Skene Keith.

Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Introduction to the treatment of disease by galvanism / by Skene Keith. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    be taken, such as copper and zinc, and brought cogether, it would certainly be found, on using suitable apparatus for testing, that the zinc is electro- positive to the copper or to state the case differently, the copper is electro-negative to the zinc. The elec- trical difference is, however, not great, but with such difference as there is, would it be possible, by making such an arrangement as that figured, to obtain a cur- rent ? It would not be possible, for, though there Fig. 72. would, at the upper junction of the two metals, be a separation of electricities, positive passing to the zinc and negative to the copper, there would be a similar separation at the lower junction, and the zinc would therefore remain charged with positive, and the copper with negative, electricity ; there would be nothing of the nature of a circulation. A current could be ob- tained, however, if this separation at the lower junc- tion could be done away with, or its effects neutralized; while, of course, retaining the separation at the upper junction. Volta's arrangement allows us to secure this, and it does so in the following way. The lower junction is done away with, and the two now disunited ends are placed in water, which is made a better conductor by the addition of some salt or acid. The water is