Dear Ginty,
The following is the manner in which I would propose treating the subject of electro-chemistry.
1. As subjects of this nature are generally mystical to a popular audience; lecturers I imagine introduce too many unexplained terms, and these when used serve only to arouse perplexity in the hearer’s mind. This cannot be remedied by appending a dry definition of each term, as this would render the lecture insufferably tedious – besides the definitions would, by nine persons out of ten, be forgotten as soon as uttered.
This I think as regards the subject before us might be obviated by running shortly through the rise and progress of these terms. This process would form an interesting part of a lecture, indeed it should be introduced as such, and the terms explained incidentally as they occur. For example, to my mind the very best way of obtaining an intelligent notion of electric action is to begin by a short illustrated description of magnetic action – A few experiments with permanent and on2 the action of the earth upon soft iron would make this sufficiently clear; the phenomena of attraction and repulsion would be exhibited, the terms poles and fluids would be made familiar and their adaptability to the case in hand exhibited in the manner which recommended the use of them to the mind of their inventor – this would undoubtedly be the most natural mode of representation.
2. From these easy beginnings we should go into electric action, making our experiments run as far as possible parallel with those already made in the case of magnetism, the point where both forces diverge and assume peculiar characteristics would in this way be strikingly exhibited.
3. Having obtained a general notion of electricity we would more strictly define its sources and here introduce the form it assumes in the Voltaic Circuit. We should begin by exhibiting an example of the simplest current possible, which any child could make, and from this ascend to the various contrivances which man have made use of and to obtain a copious and intense current.
4. These contrivances, however different in outward form depend all upon the same simple principles, and bear the common name of the galvanic battery. Grove’s battery3 would be explained, Daniells4 also, and the coal battery of Bunsen, being that used by the lecturer, would occupy his especial attention.
5. The phenomena of the Stream would be dwelt upon - how to detect its presence and direction, the laws of its action upon a fully suspended magnet and the application of these laws to the determination of the power of the current.
6. The relation of electric action to chemical action, illustrated by the decomposition which invariably attends the passage of the current through a fluid. A series of very interesting experiments might be made here; various salts might be decomposed – the component acid being visibly exhibited at one pole and the base at the other; the decomposition of water and the recombination of the gases. Electrotype, electroplating, &c would follow here as illustrations of these laws of decomposition, medallions would be made and chains gilded before the audience. To a select audience it would be of deep interest to exhibit the connexion between these phenomena and the atomic theory of Dalton. I may also remark that the mathematical treatment of the laws which regulate voltaic action would be more interesting to a similar audience than the best experiments a lecturer could exhibit.
7. But I must not forget le peuple.5 For these the heating and illuminating power of the current would be amply exhibited - metals would be smelted and the application of galvanism to blasting operations explained – the round down cliff6 and other experiments would be illustrative. The electric light would be shown and many beautiful phenomena of interference – Newton’s rings for instance – exhibited – If the Committee7 thought fit, a comparison of lights might be made and the photometer of Bunsen, a simple and beautiful method for obtaining the relative intensities of any two lights might be applied and explained.
If a select number of gentlemen wished to look more deeply into the matter, then we might introduce the various apparatus used for determining its intensity and so forth – the Tangent [Galvanometer] of Weber8 and the Rheostat of Wheatstone9 might be practically applied. By means of a combination of these two instruments and a knowledge of the laws of voltaic action we are able by the decomposition of a drop of water to calculate the amount of the earth’s magnetic force at any point upon her surface.10
RI MS JT/1/TYP/11/3702–3703
LT Transcript Only
[2 September 1850]: based on Tyndall’s journal entry for 2 September 1850, where he wrote, ‘Got a short lecture ready for the Athenaeum. Wrote to Ginty concerning it’.
permanent and on: this does not make sense. The LT transcript is incorrect; at the least the word ‘magnet’ should follow ‘permanent’. LT perhaps omitted a line.
Grove’s battery: named after William Grove (1811–96).
Daniells: named after British chemist John Frederic Daniell (1770–1845).
le peuple: the people (French).
round down cliff: on 26 January 1843, in a spectacular feat of engineering, 18,500 pounds of explosives were used to remove a large section of Round Down Cliff near Dover. (H. M. Noad, Lectures of Electricity (London: George Knight and Sons, 1844), p. 192.)
Committee: n. 1 implies that this was the Athenaeum Committee.
Tangent [Galvanometer] by Weber: an instrument used to measure minute electric currents. This refers to the galvanometer perfected by Wilhelm Weber in the early1840s. See letter 0465 for Tyndall’s use of such an instrument in his own experiments.
Rheostat of Wheatstone: a rheostat is a variable resistor used to control the current in a circuit. This refers to the rheostat invented by Charles Wheatstone.
surface: letter incomplete.
Please cite as “Tyndall0435,” in Ɛpsilon: The John Tyndall Collection accessed on 28 April 2024, https://epsilon.ac.uk/view/tyndall/letters/Tyndall0435