MOUNTAINS IN THE MOON.

Ar the present day, by means of telescopes and the labours of learned men, we actually know more of the character and appearance of the moon's surface, though it is two hundred and thirty thousand miles distant, than we do of some parts of our own globe.

As we look at the new moon with the naked eye, it is easy to perceive that the inner circle of it presents an extremely ragged line, while the outer circle is very nearly smooth. When we examine this inner edge with a strong telescope, we find a great number of luminous points, which grow larger as the sun bears upon their locality. Behind these spots a deep shade is cast, which always moves so as

These bright spots are the

to be in opposition to the sun. summits of high mountains, on which the sun shines before it reaches the lower parts; the deep shade is the shadow the mountain casts, and is always found to be in exact proportion as to length with the mountain, when the inclination of the sun's rays is taken into account. From many measurements of the length of these shadows, taken under the most favourable circumstances, the height of many of these mountains has been calculated. The highest is found to be about one English mile and three-quarters in perpendicular height, a much less height than many peaks of the Himalayan mountains of India. When it is full moon no shadows are seen on any part of her surface, because all the light falls in our line of sight. Speaking of these appearances, Sir John Herschel says: "The generality of the lunar mountains present a striking uniformity and singularity of aspect. They are wonderfully numerous, occupying by far the larger portion of the surface, and almost universally of an exactly circular or cup-shaped form: the larger have for

the most part flat bottoms within, from which rises centrally a small steep conical hill. They offer, in short, in its highest perfection, the true volcanic character, as it may be seen in the crater of Vesuvius, and in a map of the volcanic districts in the environs of Naples, or of some parts of Auvergne.. And in some of the principal ones, decisive marks of volcanic layers, arising from successive deposits of ejected matter, may be clearly traced with powerful telescopes." Of the appearance of these mountains our plate gives a beautiful illustration. It is a question still debated amongst the learned, whether these stony bodies which have fallen on the earth from the air, and are called aërolites, are not projected from these volcanic mountains in the moon.

The existence of volcanoes being admitted, it is thought possible that a stone might be shot from them with sufficient force to carry it beyond the moon's attraction. Indeed, it has been reckoned that no greater velocity is needed for this than five and a half times that of a cannon-ball; and our volcanoes have thrown out rocks which must have issued