Except the blind forces of Nature, nothing moves in this world which is not Greek in its origin.

For the first time there was constructed with this machine [locomotive engine] a self-acting mechanism in which the interplay of forces took shape transparently enough to discern the connection between the heat generated and the motion produced. The great puzzle of the vital force was also immediately solved for the physiologist in that it became evident that it is more than a mere poetic comparison when one conceives of the coal as the food of the locomotive and the combustion as the basis for its life.

God put a secret art into the forces of Nature so as to enable it to fashion itself out of chaos into a perfect world system.

In all cases of the motion of free material points under the influence of their attractive and repulsive forces, whose intensity depends solely upon distance, the loss in tension is always equal to the gain in vis viva, and the gain in the former equal to the loss in the latter. Hence the sum of the existing tensions and vires vivae is always constant. In this most general form we can distinguish our law as the principle of the conservation of force.

It will be found that everything depends on the composition of the forces with which the particles of matter act upon one another; and from these forces, as a matter of fact, all phenomena of Nature take their origin.

Natural Science treats of motion and force. Many of its teachings remain as part of an educated man's permanent equipment in life.
Such are:
(a) The harder you shove a bicycle the faster it will go. This is because of natural science.
(b) If you fall from a high tower, you fall quicker and quicker and quicker; a judicious selection of a tower will ensure any rate of speed.(c) If you put your thumb in between two cogs it will go on and on, until the wheels are arrested, by your suspenders. This is machinery.
(d) Electricity is of two kinds, positive and negative. The difference is, I presume, that one kind comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it.

Of all the forces of nature, I should think the wind contains the largest amount of motive power—that is, power to move things. Take any given space of the earth's surface— for instance, Illinois; and all the power exerted by all the men, and beasts, and running-water, and steam, over and upon it, shall not equal the one hundredth part of what is exerted by the blowing of the wind over and upon the same space. And yet it has not, so far in the world's history, become proportionably valuable as a motive power. It is applied extensively, and advantageously, to sail-vessels in navigation. Add to this a few windmills, and pumps, and you have about all. ... As yet, the wind is an untamed, and unharnessed force; and quite possibly one of the greatest discoveries hereafter to be made, will be the taming, and harnessing of it.

Somewhere in the arrangement of this world there seems to be a great concern about giving us delight, which shows that, in the universe, over and above the meaning of matter and forces, there is a message conveyed through the magic touch of personality. ...
Is it merely because the rose is round and pink that it gives me more satisfaction than the gold which could buy me the necessities of life, or any number of slaves. ... Somehow we feel that through a rose the language of love reached our hearts.

The fundamental idea of these pylons, or great archways, is based on a method of construction peculiar to me, of which the principle consists in giving to the edges of the pyramid a curve of such a nature that this pyramid shall be capable of resisting the force of the wind without necessitating the junction of the edges by diagonals as is usually done.
[Writing of his tower after its completion in 1889.]

The radical novelty of modern science lies precisely in the rejection of the belief, which is at the heart of all popular religion, that the forces which move the stars and atoms are contingent upon the preferences of the human heart.

The total quantity of all the forces capable of work in the whole universe remains eternal and unchanged throughout all their changes. All change in nature amounts to this, that force can change its form and locality, without its quantity being changed. The universe possesses, once for all, a store of force which is not altered by any change of phenomena, can neither be increased nor diminished, and which maintains any change which takes place on it.

There are various causes for the generation of force: a tensed spring, an air current, a falling mass of water, fire burning under a boiler, a metal that dissolves in an acid—one and the same effect can be produced by means of all these various causes. But in the animal body we recognise only one cause as the ultimate cause of all generation of force, and that is the reciprocal interaction exerted on one another by the constituents of the food and the oxygen of the air. The only known and ultimate cause of the vital activity in the animal as well as in the plant is a chemical process.

We ought then to consider the present state of the universe as the effect of its previous state and as the cause of that which is to follow. An intelligence that, at a given instant, could comprehend all the forces by which nature is animated and the respective situation of the beings that make it up, if moreover it were vast enough to submit these data to analysis, would encompass in the same formula the movements of the greatest bodies of the universe and those of the lightest atoms. For such an intelligence nothing would be uncertain, and the future, like the past, would be open to its eyes.

When I investigate and when I discover that the forces of the heavens and the planets are within ourselves, then truly I seem to be living among the gods.