wherein the splendid achievements of less than a quarter of a century past have not only aroused the interest and enthusiasm of the world, but already point the way to still grander triumphs yet to come. THE SOURCE AND MODE OF SOLAR ENERGY. CHAPTER I. STATEMENT OF THE PROBLEM OF SOLAR ENERGY. In endeavoring to present a new and rational interpretation of the source and mode of solar energy, based upon the established principles of recent science, it becomes necessary to briefly cite the facts bearing upon the problem to be solved and the authorities for their support, as well as to describe concisely the different hypotheses at present in vogue, and to point out the well-established insufficiency of these theories, one and all, to account for or explain the difficulties encountered, and which so far have remained as an unsolved enigma. And this problem of solar energy is the grandest and most important question of all physics, for upon the light and heat of the sun depend all physical life and its consequences, animal and vegetable, past, present, and future. If within finite time, and relatively, compared with the enormous vistas of the past, a very brief time, this source of energy is to cease, and our whole system be involved in darkness and death, such darkness and death must be eternal; for the dead sun in his final stage of condensation will be as fixed and unchangeable as the operation of eternal laws can make it, and henceforth there can be no revival or reversals, no turning back of the hand upon the dial, while the laws of nature continue; and outside the uniform operation of the laws of nature there is no source, or mode, or continuance of solar energy conceivable. It is true that when our system shall have ran down to its culmination in death, other present systems may continue for a time to exist and new ones spring into being; but these, too, must inevitably follow the same course, and likewise end in eternal darkness, until finally the great experiment of creation shall have ended in eternal failure. The changes we see in progress around us, however, are not of this nature. The individual dies, but the forces which gave life and strength to the race persist, and others will take his place, and the same forces will continue to operate with constant renewals, since we draw our light and heat and life from without; but in the death of suns and their attendant planets there is no analogous process, for such suns are constantly expending their enormous energies in the support of life external to themselves, and only the smallest part of this energy, even, can ever be utilized by themselves or by other suns or planets under any mode of interpretation now in vogue, the boundless realms of so-called inert and empty space receiving the same proportionate quota of light and heat as the almost microscopic points in the sky which constitute the suns and systems we see, and practically all,