SOME UNRECOGNISED LAWS OF NATURE.
[TO THE EDITOR OF THE "SPECTATOR."]
Sin,—In the above work—a review of which appeared in the Spectator of January 22nd—in an investigation into the causes to which thermal changes are due, we point out that if a magnet be revolved round another fixed magnet, the latter, or indeed both, will manifest an increase in tempera- ture. To which your reviewer replies most emphatically, and in italics : "No such heating effect due to the moving magnet was ever observed." To use his own expressive words, "is this guile or innocence ?" For though our experiment may be badly described, or, as described, be most inconclusive, the fact that a magnet revolving round another stationary magnet, or a piece of soft iron for that matter, generates heat, is too well known to need any special verification on our part. A magnet revolving round another stationary magnet is, as your reviewer should be aware, the root principle of all magneto-electric machines, the germ whence the more complicated machines now in use have evolved. And it is one of the most important problems in the construction of dynamos to get rid of and reduce to a minimum the amount of heat generated during working. Of course your reviewer may again contend that this heat is due to other causes. Into this discussion it is quite unnecessary for me to enter here ; but as throwing light on the question I would recommend to his notice the following statement of Professor J. A. Ewing, who in his well-known work on "Magnetic Induction in Iron and other Metals" (§ 80), when speaking of the "Heating Effects of a Cyclic Process," says : "Iron and other metals become warmed when their magnetism is successively reversed or varied in any way." (The italics are mine.) The omission marks refer to a sug- gested explanation of the fact—" magnetic hysteresis "—but, as even your reviewer must admit, for my present purpose the fact suffices without any consideration of possible or probable explanations.
One word more. In his concluding remarks your reviewer informed us that he became " dizzy " when told that "matter is merely a hypothetical assumption,"—a confession which accounts for many of his previous "sweeping statements," and throws a flood of light on his competency to criticise any philosophical work. On such a point I do not care to invoke authorities, but the following quotation from a lecture by the late Professor Huxley (" On Sensation and the Sensiferous Organs") may perhaps help to restore him to equilibrium :— "All that we know about matter is that it is the hypothetical substance of physical phenomena—the assumption of the existence of which is as pure a piece of metaphysical specula- tion as is that of the existence of the substance of mind."—I am, Sir, &c., [We do not deny that a development of beat accompanies tnagnetic changes in iron; but we do affirm that no such heating effect as Messrs. Singer and Berens observe was due to the moving magnet in their experiment. So minute, indeed, is the heat that would be developed under the cir- cumstances described that we believe the most delicate means known would fail to detect it. So that when they claim to have observed a rise of temperature of several degrees we charge them with incapability of guarding against the intrusion of experimental error. Secondly, it is the following continued equation, and not the final member of it taken alone, which staggers us :—Force =energy =power = strength = per- sistence =inertia=impulse= motion= work = pressure= weight -=mass=resistance= matter, which is merely a bypotheticil assumption. Thirdly, Mr. Berens seems to think (and chides us for not being aware) that a magnet revolving round another stationary magnet is the root-principle of all magneto-electric machines.—THE WRITER OF THE REVIEW.] [We gladly publish Mr. Lewis H. Berens's letter and our reviewer's answer, but cannot continue the discussion.— En. Spectator.]
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