Are the Planets Inhabited?

s distant as the Moon, it is necessarily 400 times as large; its surface must exceed that of the Moon by the square of 400, or 160,000; its volume by the cub

0,000

irst glance at it in a telescope is sufficient to assure the observer that he is looking at a solid, substantial globe. It is not only substantial, it is rugged; its sur

which to stand; they must have a stable terrene whereon their food may grow, and this the Moon could supply. "

of its surface receives, on the average, the same amount of light and heat that would fall upon a square yard on the Earth that was pre

photographs taken in recent years at the observatories of Paris and of the University of Chicago have shown thousands of "crater-pits," not more than a mile across; and narrow lines on the Moon's surface have been detected with a breadth less than one-tenth of this. An elevation on the Moon, if it rose up abruptly from an open plain, would ma

changes which would be plainly connected with the seasonal changes of vegetation. The Earth would present to us a disc four times the apparent diameter of the Moon, and on that disc Canada would offer as great an area as the whole of the Moon does to us. We could easily follow with the naked eye the change from the glitteri

sufficiently pronounced for us to be sure of them are ever witnessed. Here and there some slight mutations have been suspected, nearly all accomplishing their cycle

he high Sun, the contrasts are gone; the scenery appears flat, many of the large conspicuous markings are only recognized with difficulty. Thus the terse remark of M?dler, "The full Moon knows no Maginus," has become a proverb amongst selenographers; yet Maginus is a fine walled plain some eighty miles in diameter, and its r

eter, "known as Messier and Messier A, situated side by side not far from the centre of the Mare Fecunditatis. When the Sun rises first on them, the eastern one, A, is triangular and larger than Messier, which latter is somewhat pear-shaped. About three days after sunrise they both suddenly turn white, Messier rapidly grows in size, soon surpasses A, and also becomes triangular in shape. Six days after sunr

pe is probably due to the contour of the ground, conceives that, in order to explain the whole phenomenon, it is necessary to suppose that a white layer of hoar frost is formed periodically round the two craters. It is also alleged that whereas M?dler described the two craters as b

of the lunar day, and, as with Messier, some selenographers consider that it has also suffered an actual permanent change in shape within the last sixty or seventy years. Here again the evidence is not decisive; Nei

ting Sun, and filled with shadow, and the inner terraces, which should have been invisible, were seen as faint, knotted, glimmering streaks under both the eastern and western walls, and the central peak was also dimly discernible. He thought this unusual lighting up of rocks on which the Sun had already set might be due either to phosphorescence produced by long exposure to the Sun's rays, or to inherent heat, or to

ersy, and one of the most industrious of the present-day observers of the Moon, M. Philip Fauth, declares that "as a student of the Moon for the last twenty years, and as probably one of the few living invest

rom the view-point of the Earth, the Moon when examined by our most experienced observers, armed with our most powerful telescopes, offers us only a few doubtful enigmatical instances of possible change confined to small isolated localities; we see no evidence that the "gloom of iron substance" below is ever concealed by a veil o

or life. The "stability and insensibility" are indeed required in the platform upon which life is to appear

h we see them; we are able to make direct observations. Galileo, the first man to observe the Moon to better advantage than with the nake

ntains on her

sea it would be a bright line and perfectly smooth. The grey plains are therefore not expanses of water now, nor were they in time past. It is obvious that in some remote antiquity their surface was in a fluid condition, but it was the fluidity of molten rock. This is seen by the way in which the maria have invaded, breached, broken down, and submerged many of the circular formations on their margins. Thus the Mare Humorum has swept away half the wall of the rings, Hippalus and Doppelmayer, and far out in the open plain of the Mare Nubium, grea

most disconcerting; it is hardly less disconcerting to observe the reappearance at the dark limb. One moment the field of view of the telescope is empty; the next, without any sort of dawning, a bright star is shining steadily in the void, and it almost seems to the observer as if an explosion had taken place. If the Moon had an atmosphere extending upwards from its surface in all directions and of any appreciable density, an occultation would not be so exceedingly abrupt; and, in particular, if the occultation were watched through a spectroscope, then, at the disappearance, the spectrum of the star would not vanish as a whole, but

on is seen in broad daylight, it is pale and ghost-like. Sir John Herschel has put it on record that when in South Africa he often had the opportunity of comparing the Moon with the face of Table Mountain, the Sun shining full upon both, and the Moon appeared no brighter than the weathered rock. The best determinations of the albedo of the Moon, that is to say, of its reflective power, give it as 0·17, so that only one-six

As the surface absorbs heat so readily, it must radiate it as quickly; hence radiation must go on with great rapidity during the long lunar night. Lord Rosse and Prof. Very have both obtained measures of the change in the lunar heat radiation during the progress of a total eclipse of the Moon, with the result that the heat disappeared almost completely, though not quite at the same time as the light. Prof. Langley succeeded in obtaining from the Moon, far down in the long wave lengths of the infra-red, a heat spectrum which was only partly due to reflection from the Sun; part coming from the lunar soil itself, which, having absorbed heat from the Sun, radiated it out again almost immediately. In 1898, Prof. Very, following up Langley's