Page:Popular Science Monthly Volume 4.djvu/564

546 "Nor should we counsel a man to venture upon physical speculations who converts the proposition heat is insensible motion into insensible motion is heat, and hence concludes that when a force is applied to a mass so large that no motion is seen to result from it, or when, as in the case of sound, motion gets so dispersed that it becomes insensible, it turns to heat."

Respecting the first of the two statements contained in this sentence, I will observe that the reader, if not misled by the quotation-marks into the supposition that I have made, in so many words, the assertion that "insensible motion is heat," will at any rate infer that this assertion is distinctly involved in the passage named. And he will infer that the reviewer would never have charged me with such an absurd belief, if there was before him evidence proving that I have no such belief. What will the reader say, then, when he learns, not simply that there is no such statement, and not simply that on the page referred to, which I have ascertained to be the one intended, there is no such implication visible, even to an expert (and I have put the question to one), but when he further learns that, in other passages, the fact that heat is the one only of modes of insensible motion is distinctly stated (see "First Principles," §§ 66, 68, 171), and when he learns that elsewhere I have specified the several forms of insensible motion? If the reviewer, who looks so diligently for flaws as to search an essay in a volume he is not reviewing to find one term of an incongruity, had sought with equal diligence to learn what I thought about insensible motion, he would have found in the "Classification of the Sciences," Table II., that insensible motion is described by me as having the forms of heat, light, electricity, magnetism. Even had there been, in the place he names, an unquestionable implication of the belief which he ascribes to me, fairness might have led him to regard it as an oversight, when he found it at variance with statements I have elsewhere made. What, then, is to be thought of him when, in the place named, no such belief is manifest, either to an ordinary reader or a specially-instructed reader?

No less significant is the state of mind betrayed in the second clause of the reviewer's sentence. By representing me as saying that, when the motion constituting sound "gets so dispersed that it becomes insensible, it turns to heat," does he intend to represent me as thinking that, when sound-undulations become too weak to be audible, they become heat-undulations? If so, I reply that the passage he refers to has no such meaning. Does he then allege that some part of the force diffused in sound-waves is expended in generating electricity, by the friction of heterogeneous substances (which, however, eventually lapses from this special form of molecular motion in that general form constituting heat), and that I ought to have thus qualified my statement? If so, he would have had me commit a piece of scientific pedantry hindering the argument. If he does not mean either of these things, what does he mean? Does he contest the truth of the