rapid.  With each revolution a larger band of space was swept clear of its material.  With each passage of the forming globe the matter from the adjacent spaces would rush down upon its surface, and as the mass of the planet increased the process would be stimulated; for gravitation is proportional to the mass.  At length a great tubular space would be formed, having the orbit of the earth for its centre, and in this space the matter was all swept up.  The tube enlarged with each revolution, until an open way was cut through the nebular disc, and then from the one side toward Venus and from the other side toward Mars the space widened and widened, until the globe took approximately by growth its present mass of matter.  The nebulous material was drawn out of the inter-planetary space where it was floating, and the shower of star dust on the surface of the earth became thinner and less frequent.  In some parts of the orbit bands or patches of this material existed, and the earth in passing through such hands drew down upon itself the flying fragments of such matter as it continues to do to the present day.  What are meteoric displays but the residue of the primordial showers by which the world was formed?

All this work, according to the New Astronomy, took place while our globe was still in a superheated condition.  The mass of it had not yet settled into permanent form.  The water had not yet become water; it was steam.  The metals had not yet become metals; they were rather the vapor of metals.  At length they were the liquids of metals, and at last the solids.  So, also, the rocks were transformed from the vaporous through the liquid into the solid form—­all this while the globe was in process of condensation.  It grew smaller in mathematical measurements at the same time that it grew heavier by the accretion of matter.  At last the surface was formed, and in time that surface was sufficiently cooled to allow the vapors around it to condense into seas and oceans and rivers.  There were ages of superficial softness—­vast epochs of mud—­in which the living beings that had now appeared wallowed and sprawled.

We cannot trace the world-growth through all its stages but can only indicate them as it were in a sketch.  The more important thing to be noted is the relation of our planet in process of formation to the great fact called life.  Here the New Astronomy comes in again to indicate, theoretically at least, the philosophy of planetary evolution.  Each planet seems to pass through a vast almost inconceivable period in which its condition renders life on its surface or in its structure impossible.  Heat is at once the favoring and the prohibitory condition of life.  Without heat life cannot exist; with too great heat life cannot exist.  With an intermediate and moderate degree of heat many forms of animate and inanimate existence may be promoted.