e servile
image of what is in existence here below. Terrestrial organic forms are
due to local causes upon our planet. The chemical constitution of water
and of the atmosphere, temperature, light, density, weight, are so many
elements that have gone to form our bodies. Our flesh is composed of
carbon, nitrogen, hydrogen, and oxygen combined in the state of water,
and of some other elements, among which we may instance sodium chloride
(salt). The flesh of animals is not chemically different from our own.
All this comes from the water and the air, and returns to them again.
The same elements, in very minute quantities, make up all living bodies.
The ox that browses on the grass is formed of the same flesh as the man
who eats the beef. All organized terrestrial matter is only carbon
combined in variable proportions with hydrogen, nitrogen, oxygen, etc.

But we have no right to forbid Nature to act differently in worlds from
which carbon is absent. A world, for example, in which silica replaces
carbon, silicic acid carbonic acid, might be inhabited by organisms
absolutely different from those which exist on the Earth, different not
only in form, but also in substance. We already know stars and suns for
which spectral analysis reveals a predominance of silica, _e.g._, Rigel
and Deneb. In a world where chlorine predominated, we might expect to
find hydrochloric acid, and all the fecund family of chlorides, playing
an important part in the phenomena of life. Might not bromine be
associated in other formations? Why, indeed, should we draw the line at
terrestrial chemistry? What is to prove that these elements are really
simple? May not hydrogen, carbon, oxygen, nitrogen, and sulphur all be
compounds? Their equivalents are multiples of the first: 1, 6, 8, 14,
16. And is even hydrogen the most simple of the elements? Is not its
molecule composed of atoms, and may there not exist a single species of
primitive atom, whose geometric arrangement and various associations
might constitute the molecules of the so-called simple elements?

In our own solar system we discover the essential differences between
certain planets. In the spectrum of Jupiter, for instance, we are aware
of the action of an unknown substance that manifests itself by a marked
absorption of certain red rays. This gas, which does not exist upon the
Earth, is seen still more obviously in the atmospheres of Saturn and
Uranus. Indeed, upon this last planet the atmospher