VIII. Man's First Ancestors

When we retrace still further the earth's evolutionary history—further back even than we have done in the foregoing pages—we find our celestial globe composed of ever finer conditions of matter. The matter which later became solid was, at a previous stage, liquid; before that, gaseous and of the nature of vapour; while at a still remoter period we find it in its finest form, that is to say, as ether. The decrease of temperature, however, caused the gradual solidification of matter.