s called "energy of
position," that is, the outer parts of our primitive nebula had a very
long distance through which to travel towards one another in the slow
process of concentration; and this distance was the measure of the
quantity of work possible to our system. As the particles of our nebula
drew nearer and nearer together, the energy of position continually lost
reappeared continually as heat, of which the greater part was radiated
off, but of which a certain amount was retained. All the gigantic
amount of work achieved in the geologic development of our earth and
its companion planets, and in the development of life wherever life may
exist in our system, has been the product of this retained heat. At the
present day the same wasteful process is going on. Each moment the sun's
particles are losing energy of position as they draw closer and closer
together, and the heat into which this lost energy is metamorphosed is
poured out most prodigally in every direction. Let us consider for a
moment how little of it gets used in our system. The earth's orbit is
a nearly circular figure more than five hundred million miles in
circumference, while only eight thousand miles of this path are at any
one time occupied by the earth's mass. Through these eight thousand
miles the sun's radiated energy is doing work, but through the remainder
of the five hundred million it is idle and wasted. But the case is far
more striking when we reflect that it is not in the plane of the earth's
orbit only that the sun's radiance is being poured out. It is not an
affair of a circle, but of a sphere. In order to utilize all the solar
rays, we should need to have an immense number of earths arranged so as
to touch each other, forming a hollow sphere around the sun, with the
present radius of the earth's orbit. We may well believe Professor
Tyndall, therefore, when he tells us that all the solar radiance we
receive is less than a two-billionth part of what is sent flying through
the desert regions of space. Some of the immense residue of course hits
other planets stationed in the way of it, and is utilized upon their
surfaces; but the planets, all put together, stop so little of the total
quantity that our startling illustration is not materially altered by
taking them into the account. Now this two-billionth part of the solar
radiance poured out from moment to moment suffices to blow every wind,
to raise every cloud, to drive every engine, to bui