volcanoes nowadays, we are tempted to look at some of the smaller globes of the solar system and see whether they can possibly be the abodes of the great volcanoes by whose explosions meteorites have been emitted. We might, at all events, hope by such a supposition to get rid of the initial difficulty with regard to the high speed of projection, for as a low velocity will suffice to carry bodies quite clear of a small globe, it follows that we should not in such a case demand an exceptionally potent volcano.
It has, indeed, been maintained, by at least one distinguished astronomer, that in all probability meteorites are bodies which have taken their departure from volcanoes in the moon. No doubt, so far as the initial velocity is concerned, this supposition would obviate the fundamental difficulty. In the first place, about a fifth of that velocity would be required which would be necessary to discharge a missile with the critical speed from the earth. We know, also, that there is abundant testimony as to the former existence of volcanoes in the moon. That side of our satellite which alone is visible from the earth, is marked over with hundreds of craters, indicating the intense volcanic activity which once reigned there. There can hardly be any doubt that their efficiency may have been ample to impart to the missile a speed sufficiently great. Indeed, the circumstances which we know with regard to Krakatoa seem to show that some of the bombs launched from this volcano in the memorable eruption, issued from the mouth of the crater with a velocity which can hardly have fallen short of a mile a second. In other words, if a volcano like Krakatoa were to break out to-day on the surface of the moon, and if it were to discharge its missiles upwards with velocities comparable with those
