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journey than can the untutored child. He can only impress upon the mind of his followers the magnitude of the problem.

Nothing can give us a better conception of the enormous distance of the stars than the reflection that notwithstanding the rapid motion, carrying us unceasingly forward through all the ages that the human race has existed on earth, ordinary observation would fail to show any change in the appearance of the constellation toward which we are travelling. From what we know of the distance of Vega we have reason to suppose that our solar system will not reach the region in which that star is now situated until the end of a period ranging somewhere between half a million and a million of years from the present time.

It does not follow, however, that our posterity, if any such shall then live on the earth, will find Vega when they arrive at its present place. It also is going on its own journey and is passing away from its present location almost as rapidly as we are approaching it.

What is true of our sun and of Vega is true, so far as we know, of every star in the heavens. Each of these bodies is flying straight ahead through space like a ball shot out from a cannon, with a speed which in most cases is almost inconceivable. It would be a very slow moving star of which the velocity did not exceed that of a cannon shot. In the great majority of cases it ranges from five to thirty miles per second—frequently more than fifty miles. Indeed there are two stars, of which Arcturus is one, whose speed we have reason to believe approaches