bation. Another consequence: we have just said that the cube of the houses might be, on Mars, proportional to the cube of our houses. But if boards of health should proceed there according to the same principles as with us, they would have to order larger and higher rooms. It may be suggested that the atmosphere of Mars is less dense than ours, because it is not so thick, and gravity is less there. Here is, indeed, a great difficulty, which, fortunately, it is not necessary to resolve, because the law of Laplace supposes that the density is the same at homologous points. On the surface of Mars the air, then, has the same density and the same composition as on the surface of the earth. But will the inspirations be as long? The diaphragm of the Martians has not the same work to do as that of the earth people. It is true that it is only half as thick, but its surface is only a quarter, and the amplitude of its movement only one half. But we must not discuss the rhythm of the diaphragm or the beatings of the heart unless we shorten the days and increase the number in a year.
We see that whichever way we turn we can not for an instant entertain the illusion that an earth-man could be put on Mars without knowing it.
We shall fall into more and more inextricable difficulties if we go further into the detail of the respiratory and circulatory phenomena. The capillary vessels of the Martians are four times narrower in section. The heart, then, would have to use more force to make the blood circulate; yet the heart is much weaker, with thinner walls, smaller cavities, etc. Even if the Martians resemble men externally, their whole interior organization must be decidedly very different.
The persistency will be remarked with which the number four recurs in these calculations. This is because weight is reduced one half on Mars, and also, because of the reduction in their linear dimensions, the Martians have to exercise only half the effort to produce the same apparent effect. It might be concluded from this that if the universe was reduced geometrically in the proportion of three or of five to one, we should immediately find ourselves nine or twenty-five times lighter, stronger, and more active. By an inverse conclusion, if we could imagine the case for a few moments, we should have to be three or five times larger. Hence the paradoxical conclusion that the smaller the world is, the larger its people should be; so that, if the smallest asteroids are inhabited by men, the inhabitants would be more important in size than their planet, and might, in case of extremity, take it in their arms. On the other hand, the larger the planetary mass, the smaller the men should be, if their muscular sensations are comparable to ours.