e earth. It has been a
favourite idea of many believers in other worlds than ours, that though
in each world the same races of animals exist, they would be differently
proportioned; and there has been much speculation as to the probable
size of men and other animals in worlds much larger or much smaller than
the earth. When as yet ideas about other worlds were crude, the idea
prevailed that giants exist in the larger orbs, and pygmies in the
smaller. Whether this idea had its origin in conceptions as to the
eternal fitness of things or not, does not clearly appear. It seems
certainly at first view natural enough to suppose that the larger beings
would want more room and so inhabit the larger dwelling-places. It was a
pleasing thought that, if we could visit Jupiter or Saturn, we should
find the human inhabitants there

In bigness to surpass earth's giant sons;

but that if we could visit our moon or Mercury, or whatever smaller
worlds there are, we should find men

Now less than smallest dwarfs, in narrow room
Throng numberless, like that pygmaean race
Beyond the Indian mount; or fairy elves,
Whose midnight revels, by a forest side
Or fountain, some belated peasant sees,
Or dreams he sees.

Later the theory was started that the size of beings in various worlds
depends on the amount of light received from the central sun. Thus
Wolfius asserted that the inhabitants of Jupiter are nearly fourteen
feet high, which he proved by comparing the quantity of sunlight which
reaches the Jovians with that which we Terrenes receive. Recently,
however, it has been noted that the larger the planet, the smaller in
all probability must be the inhabitants, if any. For if there are two
planets of the same density but unequal size, gravity must be greater at
the surface of the larger planet, and where gravity is great large
animals are cumbered by their weight. It is easy to see this by
comparing the muscular strength of two men similarly proportioned, but
unequal in height. Suppose one man five feet in height, the other six;
then the cross section of any given muscle will be less for the former
than for the latter in the proportion of twenty-five (five times five)
to thirty-six (six times six). Roughly, the muscular strength of the
bigger man will be half as great again as that of the smaller. But the
weights of the men will be proportioned as 125 (five times five times
five) to 216 (six times six times six), so that th