there be a lake of a fixed level, and communicating with it and with each other, by open channels, two ponds of water occupying an island in the middle of the lake. If one of these ponds be higher in level and the other lower than the lake, their waters will rapidly converge, the higher flowing into the lower; but if both are at the same level, and higher than the lake, they will flow apart into the lake. Or, if both are at the same level, and lower than the lake, the water of the latter will equally flow from outside into both ponds, and their waters will still be held separate from each other. The analogies of these various levels may be pursued to any desired extent, as electrical tensions find their most exact analogies in the pressures of bodies of water at different levels and of different quantities, and these analogies are those most constantly used in the interpretation of such electrical phenomena. The great electrical activity of the electrospheres of the earth and moon, while they discharge their tremendous currents directly into the sun, at the same time must cause their similarly electrified atmospheres to mutually repel each other, while gravity continues to operate to maintain the earth and moon at their fixed distances from each other, and to retain their gaseous envelopes around their own bodies. The result must be that these similarly electrified atmospheres repel each other with a force proportioned to their masses of atmosphere and the intensity of the electricities of each. The moon's axial rotation being completed but once in twenty-eight days, and that of the earth once in each day, and the moon's mass and volume being so much less than those of the earth, whatever of electrified air or moisture she may have (and she must have both, proportionate to her attributes) would have been driven as by a cyclone to the opposite side of the moon and there retained. Now, with an atmosphere and water only on one side of the moon, and that the side opposite the earth, it is obvious that a rotation on her axis at all resembling that of the earth would carry every part of her surface, at each complete rotation, from a region of air and moisture into one deprived of both, and in such a condition she would of necessity be deprived of both life and its possibility; hence, as the laws of nature compel the lunar atmosphere and moisture to reside permanently on the side always opposite the earth, a co-ordinate arrest of the moon's axial motion with reference to the earth could alone compensate for such a state of things, and, curiously enough, we find as a solitary exception, compared with the planets, that such is the case. The moon unquestionably has both atmosphere and water on its opposite side. In his recent work, "In the High Heavens," Professor Ball reviews the physical conditions of the other planets as possible abodes of life. He pronounces against the moon because night and day would each be a fortnight in length;