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 to the tremendous volcanic power necessary to impart the acquired velocity to the missile. Quite a moderate volcano placed on such a globe would undoubtedly shoot bodies upwards that would not return. But here, again, we have to remember that before such a missile could descend to our earth as a meteorite, it is necessary for the circumstances of projection to be such that the body shall take a direction which will ultimately cause it to strike the earth. The conditions that this implies are of very great importance. It will be necessary to consider them.

If a meteorite projected from a volcano on Ceres is ever to strike the earth it must, it need hardly be said, pass through that narrow strip in the ecliptic, some eight thousand miles wide, which the earth traces out in its annual movements. I say narrow strip, for although it may seem that eight thousand miles is a considerable width, it must be remembered that on the scale on which the orbit has to be drawn the width named would only correspond to an extremely fine line. The projectile from the planet, as it quits the neighbourhood of the parent globe, becomes appreciably affected by the attraction of the sun, and as its distance from the planet increases, the attraction of that planet dwindles to evanescence, while the attraction of the sun becomes the predominating influence by which the movement is guided. The projectile accordingly pursues a track in accordance with the known laws of planetary motion. We are therefore to think of the little body as revolving around the sun in the same manner as the planet itself revolves, only possibly with an orbit considerably more eccentric, and inclined at a much larger angle to the ecliptic than that at which orbits are generally placed. If, therefore,