The Complete Works of Edgar Allan Poe - Edgar Allan Poe [113]
April 18th. To-day I found an enormous increase in the moon's apparent bulk – and the evidently accelerated velocity of my descent, began to fill me with alarm. It will be remembered, that, in the earliest stage of my speculations upon the possibility of a passage to the moon, the existence, in its vicinity, of an atmosphere, dense in proportion to the bulk of the planet, had entered largely into my calculations; this too in spite of many theories to the contrary, and, it may be added, in spite of a general disbelief in the existence of any lunar atmosphere at all. But, in addition to what I have already urged in regard to Encke's comet and the zodiacal light, I had been strengthened in my opinion by certain observations of Mr Schroeter, of Lilienthal. He observed the moon, when two days and a half old, in the evening soon after sunset, before the dark part was visible, and continued to watch it until it became visible. The two cusps appeared tapering in a very sharp faint prolongation, each exhibiting its farthest extremity faintly illuminated by the solar rays, before any part of the dark hemisphere was visible. Soon afterwards, the whole dark limb became illuminated. This prolongation of the cusps beyond the semicircle, I thought, must have arisen from the refraction of the sun's rays by the moon's atmosphere. I computed, also, the height of the atmosphere (which could refract light enough into its dark hemisphere to produce a twilight more luminous than the light reflected from the earth when the moon is about 32° from the new,) to be 1356 Paris feet; in this view, I supposed the greatest height capable of refracting the solar ray, to be 5376 feet. My ideas on this topic had also received confirmation by a passage in the eighty-second volume of the Philosophical Transactions, in which it is stated, that, at an occultation of Jupiter's satellites, the third disappeared after having been about 1" or 2" of time indistinct, and the fourth became indiscernible near the limb3.
3 Hevelius writes that he has several times found, in skies perfectly clear, when even stars of the sixth and seventh magnitude were conspicuous, that, at the same altitude of the moon, at the same elongation from the earth, and with one and the same excellent telescope, the moon and its maculæ did not appear equally lucid at all times. From the circumstances of the observation, it is evident that the cause of this phenomenon is not either in our air, in the tube, in the moon, or in the eye of the spectator, but must be looked for in something (an atmosphere?) existing about the moon.
Cassini frequently observed Saturn, Jupiter, and the fixed stars, when approaching the moon to occultation, to have their circular figure changed into an oval one; and, in other occultations, he found no alteration of figure at all. Hence it might be supposed, that at some times, and not at others, there is a dense matter encompassing the moon wherein the rays of the stars are refracted.
Upon the resistance, or more properly, upon the support of an atmosphere, existing in the state of density imagined, I had, of course, entirely depended for the safety of my ultimate descent. Should I then, after all, prove to have been mistaken, I had in consequence nothing better to expect, as a finale to my adventure, than being dashed into atoms against the rugged surface of the satellite. And, indeed, I had now every reason to be terrified. My distance from the moon was comparatively trifling, while the labor required by the condenser was diminished not at all, and I could discover no indication whatever of a decreasing rarity in the air.
April 19th. This morning, to my great joy, about nine o'clock, the surface of the moon being frightfully near, and my apprehensions excited to the utmost, the pump of my condenser at length gave evident tokens of an alteration in the atmosphere. By ten, I had reason to believe its density considerably increased. By eleven, very little labor was necessary at the apparatus; and at twelve o'clock, with some