of Jupiter and the Mero-planets; and when, at length, he has reached the orbit of Mars, the disc of the earth has become visible, and the rich blue tint of our planet is conspicuous over all the others. Onward and onward the pilgrim angel flies, keeping our little planet still before him, until its growing disc expands into a gigantic moon; and, in a few minutes more, he dips beneath the blue atmosphere that covers the Babylonian plains, and lays his hand upon the prostrate Daniel. It is the time of the evening oblation. CHAPTER XXXV. THE GEOLOGY OF THE MOON. (A CHAPTER ADDITIONAL to the FIRST PART.) IN preparing the previous chapters for the press, and, after the first part had been printed, the author was led to pass under review the various phenomena connected with the moon, and to examine whether they might not be accounted for, without supposing that there is any difference between the materials of our earth, and those of which its satellite is composed. The speculations to which this inquiry gave rise involve so many interesting questions, that, although he has not had time to subject them to careful scrutiny, he cannot deny himself the present opportunity of offering them to the consideration of others, as well as himself. There are five grand enigmas which present themselves for solution when we study the constitution of the moon. 1. Why should the moon's rotation on its own axis so exactly coincide with its revolution round the earth? 2. Why should the moon be so much lighter than the earth, in regard to its specific gravity, if it be composed of the same kind of materials? Its proportionate density is only 615, supposing the earth's specific gravity to be 1000. 3. How can we account for those strange geographical features which we observe in the moon, particularly those great circular basins, multitudes of which cover so large a portion of its surface? 4. How can we account for the entire absence of an atmosphere around the moon, and the want of water on its surface, if the moon be composed of the very same kind of materials as the earth? Were there no gaseous oxides produced during its formation? Was there no hydrogen present to form water, no carbon to form carbonic acid? Or even, in the absence of these, how can we account for the fact, that so large a body as the moon should fail to attract towards it a condensed envelope drawn from the general atmosphere of the solar system? 5. How can we account for those luminous spots which appear on the darkened surface of the moon, sometimes equal in brilliancy to stars of the sixth magnitude, when we know, from observation, that there are no living volcanoes at present existing upon it? These are the questions which we now propose to answer, believing that all of them may be satisfactorily disposed of, on the supposition that the materials of which the moon is composed. are in no respect different from those of the earth, and, indeed, that the whole of the five phenomena may be explained more easily than if any one of them had been wanting. Let us then suppose that the moon, when the oxidation of its materials was completed, formed a mass of liquid incandescent lava, surrounded by an atmosphere of common air, saturated with aqueous vapour, in the same proportions with the atmosphere and ocean which have fallen to the share of the earth. That is to say, as the |