On the results of a series of experiments on the decomposition of water by the galvanic battery : with a view to obtain a constant and brilliant lime light / by N.J. Callan.

  • Callan, N. J. (Nicholas Joseph), 1799-1864.
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: On the results of a series of experiments on the decomposition of water by the galvanic battery : with a view to obtain a constant and brilliant lime light / by N.J. Callan. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    changed move frequently than the lime; and there is more reason to fear that the coke light will fail on account of the destruction of the positive coke point, than that the lime light will go out on account of the wearing of the lime. For the coke light, the zinc plates should not contain more than 8 square inches of sur- face. If they be larger, the positive coke point will be rapidly destroyed, without a proportional increase of light. The sixth result is a new mode of exhibiting the dissolving views by means of the lime light. In the common apparatus for showing the dissolving views, the apertures of the lanterns are gradually opened and gradually closed, in order to make the figures come gradually into view and gradually disappear. By using the mixed gases, the apertures may be left always open, and the figure in either lantern may be gradually brought out on the screen, and may be made to fade away by degrees; for by opening very slowly the stopcock through which the gases pass to the jet, the light in the lanterns may be made to increase very slowdy till it has acquired its full intensity, and consequently the image thrown on the screen will become gradually brighter till it attains its full brightness; and by very slowly closing the stopcock, the light, and consequently the image, will gradually fade away. By exhibiting the dissolving views in this way, there is a great saving of the mixed gases; for the light shines out fully in each lantern only when it is necessary to exhibit the image in full brightness on the screen. Besides, by diminishing the quantity of the gases which passes through one jet, the quan- tity which passes through the other jet, and consequently the brightness of the full image, is increased. The last result is a new sine galvanometer, which is the only instrument yet devised for measuring with accuracy very power- ful galvanic currents*. Some of my experiments raised doubts in my mind about some of the generally received theories relating to the action of the galvanic battery. The galvanometers which I had were not fit for measuring very powerful currents, such as I employed. I wras therefore obliged to get a new one. After a good deal of reflection, I resolved to get one which would answer for a sine instrument, for the common tangent instru- ment, and for the new tangent galvanometer, the principle of which is demonstrated in the Comptes Rendus of the 24th of last January. The galvanometer which I have made consists of a mahogany circle 2 feet 4 inches in diameter and nearly 2 inches thick, in the circumference of which is turned a groove half an inch wide and 3| inches deep ; of seven concentric coils of |-inch copper wire in the groove, and well insulated from each other; of a strong frame in which the circle is moveable on an axis, and * The voltameter will not measure powerful currents produced by a single «ircle, or by two or three circles.