practise; proposes the utilization of the bodies of condemned criminals for experiments on the etiology of disease; calls for the prosecution of systematic experiments with electricity, and the abandonment of premature efforts to make practical use of that force, before its properties and behavior had been adequately investigated; and indicates the possibility of the prosecution of certain expériences métaphysiques—i. e., of investigations in what we should now call experimental psychology. He concludes his program somewhat humorously with an enumeration of récherches à interdire—namely, those 'chimeras of science,' the philosopher's stone, the quadrature of the circle and perpetual motion. In regard to the first of these, however—the transmutation of elements—he points out that the thing can not be shown to be inherently impossible. For there are several legitimate hypotheses about the constitution of matter which are compatible with the possibility of transmutation. It is not unlikely, for example, that 'matter is composed of homogeneous parts,' and that the elements which appear to possess irreducible qualitative differences, 'really differ from one another only by the dissimilar form and arrangement of the homogeneous particles which compose them.' In that case, we should not be entitled to declare it impossible to give 'to such particles a different form and arrangement, which is all that would be necessary in order to transmute lead or wool into gold.' The objection to the search for the means of transmuting elements is, therefore, not that it can be demonstrated to aim at the impossible, but only that in the existing state of science, the value of the goal—great as it would be—'is not great enough to counterbalance the scant probability of attaining it.' When one reminds oneself of the hypotheses about the constitution of matter that have come into especial vogue since the discovery of the properties of radium, these observations strike one as the expression of a rather well balanced judgment.
It was, however, in his conception of the methods and the possibilities of natural history that Maupertuis most evidently showed himself the possessor of a wider intellectual horizon than was common among the men of science of his time. Zoologists had as yet seen little occasion to attempt more than the careful description and classification of animals; but to Maupertuis a purely descriptive and classificatory science, which was unable to formulate any laws concerning the processes going on in that part of nature with which it dealt, was, strictly speaking, no science at all. He had little patience with naturalists whose view of their province was so narrow. 'All these treatises on animals which we as yet have,' he writes in the 'Lettres sur le Progrès des Sciences,' 'are—even the most methodical of them—: no better than pictures pretty to look at; in order to make of natural history a veritable science, naturalists must apply themselves to researches which can make us acquainted, not simply with the form of this or that animal, but with the general