that Professor Newcomb is a prominent scientist, at the head of a scientific bureau in Washington; while the author of the book he professes to review, if known at all, is known only in connection with pursuits which are generally supposed to preclude, not only distinction but even reputable standing in the domains of scientific investigation. I take the liberty, therefore, to subject the strictures of my critic to a counter-critical examination, trusting that the learned professor himself will find it thorough, and that the reader who has not only perused his article, but also looked into a chapter or two of my book, will recognize it as neither impertinent nor unfair.
Whatever may be thought of the soundness or unsoundness of the general argument of the little book in question, the drift of that argument, it seems to me, can hardly be mistaken by the reasonably intelligent reader. What I attempt to show is simply this: that modern physical science aims at a mechanical interpretation of physical phenomena, seeking to effect a reduction of them to two elements which are ordinarily designated as matter and motion, but which (for reasons briefly stated in the book, but to be stated more at length presently) are more correctly designated as mass and motion. I then attempt to show that, if to these premises we add the assumption of the atomic constitution of matter, the mechanical theory necessarily involves four distinct propositions, relating severally to the equality, inertia, and inelasticity of the atoms or ultimate molecules and the essentially kinetic character of what is now universally termed energy. In order to enforce the irrecusability of these propositions on the basis of the atomo-mechanical theory, and to guard against the imputation that I am engaged in the frivolous pastime of chopping logic, I am at pains to show, in the next four chapters, that every one of these propositions is insisted on and propounded in terms identical with, or equivalent to, those in which I state them, by men whom I was under the delusion, up to the time of the appearance of Professor Newcomb's article, of regarding as persons of the highest scientific authority—such men as Professors Du Bois-Reymond, Thomas Graham, Wundt, etc. I then proceed to inquire what is the relation of these propositions to the sciences of chemistry, physics, and astronomy, as they are actually constituted, endeavoring to ascertain whether or not the fundamental propositions of the atomo-mechanical theory are available as theoretical solvents of the facts with which these sciences are conversant, and whether or not they are consistent with them. The result of this inquiry is, that the man of science, however emphatic he may be in the general assertion that all physical phenomena are due to the interaction of atoms or ultimate molecules, is constrained by the data of scientific experience to repudiate and discard the propositions which his assertion necessarily involves. It thus appears that there is conflict between the facts and working hypotheses or theories of the sciences on the one hand and the atomo-mechanical theory on the