After attentive consideration of the various points which have now been discussed, it will, I think, be admitted that the great initial velocity which the terrestrial theory of meteorites demands can no longer be deemed an insuperable objection to its acceptance. We need not ask that the necessary violence shall have been manifested very often in comparison with the total number of volcanic outbreaks. All we demand is, that during the millions of years in which the crust of the earth has been consolidating there shall have been occasionally outbreaks of sufficient vehemence to have discharged clouds of fragments with such energy that they shall leave the earth, or rather the earth's atmosphere, with a velocity of not less than six miles a second. If this be granted, then the explanation of the origin of the meteorites is complete.
Each little particle after taking leave of the earth to commence its voyage through space, will be acted upon by the attraction of the sun. To a certain extent, of course, the attraction of the earth must also affect the movement of the body, but after a time it will generally happen that the attraction of the sun will become of paramount importance in the control of the movement. This will be obvious when it is remembered that the sun is more than three hundred thousand times as massive as the earth, and that therefore at equal distances the potency of the sun's attraction when compared with that of the earth is to be expressed by the same number. We know that the attraction varies inversely as the square of the distance, so that by the time the missile has reached a point which is about the five-hundredth part of the present distance between the earth and the sun, the attraction of these two bodies on the missile will be equal. In fact, long ere the little
