a mile. The diminished gravitation would prove of service in athletic performances on the moon. Not only would a bicycle be driven along with unparalleled ease and rapidity if the lunar roads were smooth, but even the disagreeable process of taking a header over the handles would lose its terrors, for the lunar bicyclist would fall gently and softly to his mother earth. It may, however, be questioned whether our bodies would be adapted for a life under such conditions. It seems almost certain that as the muscular system of the human body has been arranged to work with the particular gravitation that is found on this earth, it would be impossible for it to be accommodated to a gravitation which had only a sixth of the intensity for which it was adapted. On these grounds we conclude that neither the times nor the seasons, neither the gravitation nor the other distinctive features of the moon, would permit it to be an endurable abode for life of the types we are acquainted with.
Let us now consider some of the more distant worlds, and examine their claims to be regarded as possible homes for beings in any degree resembling ourselves. There are many of these worlds with regard to which we may at once decide in the negative. Could we, for instance, live on a planet like Neptune? It lies thirty times as far from the sun as we do. The share of the light and heat from the sun which a Neptunian inhabitant would receive could only be the nine-hundredth part of that which is dispensed to every dweller on this earth. This fact alone would seem to show an insuperable obstacle to the existence of any life on Neptune resembling those types of life with which we are familiar. The orbit of
