Dynamical Enunciations

Abstract

I AM much obliged to the Editor of NATURE for giving me an opportunity of commenting upon Prof. Barton's letter. In the second edition of my book on “Theoretical Mechanics” I have expressed my ideas on the subject at such length that it is unnecessary to go into details here. It may suffice to say that the first two of Prof. Barton's proposed enunciations seem to me to be too abbreviated to be of much value. To anyone who understands the theory of mechanics, as explained by the writers whom he cites, such statements could be of little use, while to anyone who does not they might be misleading. The third enunciation does not distinguish between force and the quantity which Routh called “effective force” and I call “kinetic reaction”. The distinction appears to me to be important. The fourth enunciation would seem to permit an undesirable degree of freedom in respect to the choice of a reference system. I do not wish to suggest that Prof. Barton means by his brief enunciations something different from what I mean in my book, but rather to point out that such brevity as he aims at may be inconsistent with clearness in the statement of principles. One way of bringing the results of modern critical discussions concerning the laws of motion within the reach of the “ordinary student” would be to publish a short tract, on the same scale, say, as Maxwell's “Matter and Motion”. In such a tract summary enunciations could be accompanied by adequate explanations. Would not this be better than providing teachers with a set of enunciations?