The second chapter is devoted to an exposition of the general principles of the mechanical theory, which may! very briefly summed up in four propositions, as follows:
1. The elementary units of mass being simple, are in all respects equal.
2. They are absolutely hard and inelastic.
3. They are absolutely inert, and therefore purely passive.
4. All potential energy, so called, is in reality kinetic.
In the next six chapters these propositions are taken up in their order, with the view of ascertaining to what extent they are consistent with each other, and how far they serve as explanations of the facts of scientific experience. It here comes out that there is a profound anarchy in the views of the ablest scientists regarding ultimate scientific questions. Judge Stallo discusses the accepted theories with great critical skill and logical force, showing their short-comings and contradictions, and proving conclusively that what is now most needed is a thorough-going re-examination of the grounds of what is currently regarded as established scientific theory.
The eight chapters of the work to which we here refer are worthy of being very carefully studied on their own merits as expositions and criticisms of scientific theory. But the author's analysis brings out a group of errors, of which he finds it necessary to seek the sources and parentage. This opens to him (Chapter IX) the interesting problem of the relation of thoughts to things, the formation of concepts, and the consideration of metaphysical theories. He then passes, in Chapters X, XI, and XII, to an examination of the character and origin of the mechanical theory, and points out successively how it exemplifies four radical errors of metaphysics. The nature of these errors we have no space here to explain, but the author shows that they extend much further in their vitiating influence than to the mechanical theory of the constitution of material nature. In Chapter XIII he still further develops the general argument by explaining how the same metaphysical fallacies that taint our theoretical physics have given rise to modern transcendental geometry and the new doctrine of space, with four or more dimensions. In Chapter XIV this subject of meta-geometrical space is pursued in the light of modern analysis, and by an examination of Riemann'a celebrated essay upon this subject. The further ramifications of metaphysical error in science are then followed out in Chapter XV into cosmological and cosmogenetic speculations, with a consideration of the nebular hypothesis. Chapter XVI concludes the work, with a summary of important portions of the previous discussion, and some further interesting reflections on the present attitude of chemical philosophy.
In regard to the atomic theory in chemistry, Judge Stallo does not deny its usefulness as a graphic device for representing chemical and physical transformations. He recognizes it as "a fact beyond dispute that chemistry owes a great part of its practical advance' to its use, and that the structural formulas founded upon it have enabled the chemist, not merely to trace the connection and mutual dependence of the various stages in the metamorphosis of 'elements' and 'compounds,' so called, but in many cases (such as that of the hydrocarbon series in organic chemistry) successfully to anticipate the results of experimental research."
But the convenience of hypothetical devices can not prove their truth. In the advance toward higher science, erroneous views are often the efficient instruments of progression. The history of science is full of the utilities of erroneous theory. Early astronomy, as so well shown by Whewell, was mainly developed by the help of the false theory of epicycles. Experimental chemistry, as pointed out by Liebig, originated under the influence of the false notion of the transmutability of the metals; while its later advances were largely due to the erroneous hypothesis of phlogiston. So the atomic hypothesis has carried it on still further, but this no more proves it to be true than it did the preceding hypotheses. The scaffoldings of construction, important, indispensable as they may be, arc not to be identified with the edifice.
This scanty outline of the author's argument will serve only to suggest the nature of the problems with which he is engaged. The book must be read deliberately, must be studied to be appreciated; but the students of science, as well as those of meta-
