on, and this argument is supported by the assumption that the moon was at first a mass of fluid. I do not understand this mode of making facts to support theories; and I wish you would explain to me why, in this particular instance, the inference of a divine and intentional plan in the structure of this part of the solar system is so extremely improbable. To me it seems so obvious a piece of invented mechanism, that I can not avoid the conclusion that it was the intentional work of a constructor, any more than I could if I were to find a piece of mechanism under circumstances which indicated that it was produced by human hands. KOSMICOS. You do not even yet do justice to the scientific method of reasoning. The deductions of science--the conclusions which the scientist draws from the phenomena of Nature--rest upon the postulate of fixed laws of Nature, which never change, and which have not been varied by any supernatural interference. We mean by a supernatural cause one which is not uniformly in operation, or which operates in some way different from the fixed laws which we have deduced from the observed order of the phenomena that we have studied and found to be invariable. We adopt this distinction between the natural and the supernatural because the observable phenomena of Nature do not furnish any means of discovering as a fact the operation of anything but the fixed laws, or any cause which has acted in a different way. Let us now apply this to the phenomena which we have been considering--the composition and arrangement of the solar system. What do we find? We find a system of bodies in the movements of which we detect certain fixed laws operating invariably in the same way. When the question is asked, How were these bodies produced? we have no means of reaching a conclusion except by reasoning upon the operation of the forces which these laws disclose, working on the primordial matter out of which the bodies became formed. It is for this reason that, in accounting for their existence, we speak of the method of their formation as the natural, in contradistinction to some other method which we call the supernatural; by which latter term we mean some mode in which there has been a power exerted differently from the established and fixed agency of the laws of matter, which constitute all that we have ever discovered. The nebular hypothesis affords a good illustration of the distinction which I am endeavoring to show you, whether it is well established or not, or is ever likely to be. It supposes that there was a mass of fiery vapor, floating in the space now occupied by the solar system. Under the operation of the laws of gravitation and motion, of mechanical forces and chemical combination, this crude matter becomes consolidated and formed into the different bodies known to us as the sun and the planets, and the laws which thus formed them continue to operate to keep them in the