The mere fact, however, that there is such an ether, and that it has properties related to other agents, in the way we have suggested, is well calculated to extend our views of the structure of the universe, and of the resources, if we may so speak, of the Power by which it is arranged. The solid and fluid matter of the earth is the most obvious to our senses; over this, and in its cavities, is poured an invisible fluid, the air, by which warmth and life are diffused and fostered, and by which men communicate with men: over and through this again, and reaching, so far as we know, to the utmost bounds of the universe, is spread another most subtle and attenuated fluid, which, by the play of another set of agents, aids the energies of nature, and which, filling all parts of space, is a means of communication with other planets and other systems. There is nothing in all this like any material necessity, compelling the world to be as it is and no otherwise. How should the properties of these three great classes of agents, visible objects, air, and light, so harmonize and assist each other, that order and life should be the result. Without all the three, and all the three constituted in their present manner, and subject to their present laws, living things could not exist. If the earth had no atmosphere, or if the world had no ether, all must be inert and dead. Who constructed these three extraordinary complex pieces of machinery, the earth with its productions, the atmosphere, and the ether? Who fitted them into each other in many parts, and thus made it possible for them to work together? We conceive there can be but one answer; a most wise and good God. CHAPTER XVIII. _Recapitulation._ 1. It has been shown in the preceding chapters that a great number of quantities and laws appear to have been _selected_ in the construction of the universe; and that by the adjustment to each other of the magnitudes and laws thus selected, the constitution of the world is what we find it, and is fitted for the support of vegetables and animals, in a manner in which it could not have been, if the properties and quantities of the elements had been different from what they are. We shall here recapitulate the principal of the laws and magnitudes to which this conclusion has been shown to apply. 1. The Length of the Year, which depends on the force of the attraction of the sun, and its distance from the earth. 2. The Length of the Day. 3. The Mass of the Earth, which depends on its magnitude and density. 4. The Magnitude of the Ocean. 5. The Magnitude of the Atmosphere. 6. The Law and Rate of the Conducting Power of the Earth. 7. The Law and Rate of the Radiating Power of the Earth. 8. The Law and Rate of the Expansion of Water by Heat. 9. The Law and Rate of the Expansion of Water by Cold, below 40 degrees. 10. The Law and Quantity of the Expansion of Water in Freezing.