Page:The fairy tales of science.djvu/221

Rh might be compensated by modified atmospheric conditions, will suffice to dispose of this objection. The only tenable argument against the habitableness of those large globes might be, that from their vast magnitude in comparison to the earth the effects of gravity upon them would be such as to unfit species organized like those of the latter for existence there, since they would, in fact, be crushed to pieces under the enormous pressure of their own weight. But leaving out of consideration the very obvious expedient of a proportionate adaptation of the size and weight of the bodies placed upon these globes to the respective magnitudes of the latter, a more careful examination of the question, and application of the rule, that “the weight of bodies placed upon the surface of a globe depends conjointly on the quantity of matter in the globe, and on the distance of the body from its centre,” will at once show that owing to the inferior density of the matter composing the four large planets, which in comparison to that of the matter composing the Earth, is for Jupiter as 1 to 4, for Saturn as 1 to $8 1⁄2$, for Uranus and Neptune as 1 to 6; the weight of bodies placed on the surfaces of the three latter planets actually does not differ much from their weight on the earth, whilst in the case of Jupiter, it is only $2 3⁄4$ times greater than upon the terrestrial globe.

In the case of the moon we are led to believe from the desolate bleakness of her surface, and the total absence of all indications of an atmosphere, that