From Wilhelmus Martinus van Breda; Logeman^{1, 2, 3}

XVII. On Ampèrian Repulsion. | By MM. J. G. S. van Breda and W. M. Logeman. | To Dr. Tyndall, F.R.S.

Sir,

We take advantage of the opportunity afforded by the sending of the accompanying letter, to address, through your kindness, to the readers of the Philosophical Magazine a few lines in answer to the remarks published by Mr. Croll of Glasgow,⁴ in the Number of that Journal for this month.⁵ pp. 365 et seq., in reference to our experiments on Ampèrian repulsion.

There must be, either in the description of our experiments, or in the figure which accompanies them, some want of accuracy or of clearness; otherwise we are at a loss to understand how Mr. Croll could say that the currents in the mercury ought to repel the horizontal parts, while they attract the vertical parts of our moveable conductor. This seems to us to contradict all the received ideas of electric currents. We would willingly take trouble to make our description more clear or more accurate, but the remainder of Mr. Croll’s article induces us to think that such an attempt would be quite useless.

In fact, Mr. Croll first admits that “our experiments with the reversed conductor, and some others detailed by us, certainly prove that the molecules of a conductor, while the current is passing, do repel each other;” and then goes on to discuss the question from a point of view which is new to us, adding that this repulsion of the molecules of a conductor proves nothing as to the repulsion of the contiguous parts of the current itself. Now we will not follow Mr. Croll into the arguments upon which he bases his opinion concerning the mutual action of the parts of the current; in the first place, because these arguments appear to us to be beyond the reach of experimental control; and in the second place, because we think it can be of but slight use to science to speculate on the properties of a current hypothetically detached from the material substratum without which we are unable really to conceive of its existence.

We have the honour to remain, &c., | J. G. S. van Breda, | W. M. Logeman.

Teylerian Laboratory, Haarlem, | May 1862.

J. G. S van Breda and W. M. Logeman, ‘On ampèrian repulsion’, Phil. Mag., 24 (1862), pp. 126–7.