Vol. 1. Lat. & Eng.
C. XXVI.
Fig. 1-5
CHAPTER XXVII.
OF LIGHT, HEAT, AND OF COLOURS.
[1.] Of the immense magnitude of some bodies, and the unspeakable littleness of others.—[2.] Of the cause of the light of the sun.—[3.] How light heateth.—[4.] The generation of fire from the sun.—[5.] The generation of fire from collision.—[6.] The cause of light in glow-worms, rotten wood, and the Bolognan stone.—[7.] The cause of light in the concussion of sea water.—[8.] The cause of flame, sparks, and colliquation.—[9.] The cause why wet hay sometimes burns of its own accord; also the cause of lightning.—[10.] The cause of the force of gunpowder; and what is to be ascribed to the coals, what to the brimstone, and what to the nitre.—[11.] How heat is caused by attrition.—[12.] The distinction of light into first, second, &c.—[13.] The causes of the colours we see in looking through a prisma of glass, namely, of red, yellow, blue, and violet colour.—[14.] Why the moon and the stars appear redder in the horizon than in the midst of the heaven.—[15.] The cause of whiteness.—[16.] The cause of blackness.
Of the immense magnitude of some bodies, and the unspeakable littleness of others.
1. Besides the stars, of which I have spoken in the last chapter, whatsoever other bodies there be in the world, they may be all comprehended under the name of intersidereal bodies. And these I have already supposed to be either the most fluid æther, or such bodies whose parts have some degree of cohesion. Now, these differ from one another in their several consistencies, magnitudes, motions, and figures. In consistency, I suppose some bodies to be harder, others softer through all the several degrees of tenacity. In magnitude, some to be greater, others less, and many unspeakably little. For we must remember that, by the understanding, quantity is divisible into divisibles perpetually. And, therefore, if a man could do as much with his hands as he can with his understanding, he would be able to take from any given magnitude a part which should be less than any other magnitude given. But the Omnipotent Creator of the world can actually from a part of any thing take another part, as far as we by our understanding can conceive the same to be divisible. Wherefore there is no impossible smallness of bodies. And what hinders but that we may think this likely? For we know there are some living creatures so small that we can scarce see their whole bodies. Yet even these have their young ones; their little veins and other vessels, and their eyes so small as that no microscope can make them visible. So that we cannot suppose any magnitude so little, but that our very supposition is actually exceeded by nature. Besides, there are now such microscopes commonly made, that the things we see with them appear a hundred thousand times bigger than they would do if we looked upon them with our bare eyes. Nor is there any doubt but that by augmenting the power of these microscopes (for it may be augmented as long as neither matter nor the hands of workmen are wanting) every one of those hundred thousandth parts might yet appear a hundred thousand times greater than they did before. Neither is the smallness of some bodies to be more admired than the vast greatness of others. For it belongs to the same Infinite Power, as well to augment infinitely as infinitely to diminish. To make the great orb, namely, that whose radius reacheth from the earth to the sun, but as a point in respect of the distance between the sun and the fixed stars; and, on the contrary, to make a body so little, as to be in the same proportion less than any other visible body, proceeds equally from one and the same Author of Nature. But this of the immense distance of the fixed stars, which for a long time was accounted an incredible thing, is now believed by almost all the learned. Why then should not that other, of the smallness of some bodies, become credible at some time or other? For the Majesty of God appears no less in small things than in great; and as it exceedeth human sense in the immense greatness of the universe, so also it doth in the smallness of the parts thereof. Nor are the first elements of compositions, nor the first beginnings of actions, nor the first moments of times more credible, than that which is now believed of the vast distance of the fixed stars.
Some things are acknowledged by mortal men to be very great, though finite, as seeing them to be such. They acknowledge also that some things, which they do not see, may be of infinite magnitude. But they are not presently nor without great study persuaded, that there is any mean between infinite and the greatest of those things which either they see or imagine. Nevertheless, when after meditation and contemplation many things which we wondered at before are now grown more familiar to us, we then believe them, and transfer our admiration from the creatures to the Creator. But how little soever some bodies may be, yet I will not suppose their quantity to be less than is requisite for the salving of the phenomena. And in like manner I shall suppose their motion, namely, their velocity and slowness, and the variety of their figures, to be only such as the explication of their natural causes requires. And lastly, I suppose, that the parts of the pure æther, as if it were the first matter, have no motion at all but what they receive from bodies which float in them, and are not themselves fluid.
Of the cause of the light of the sun.
2. Having laid these grounds, let us come to speak of causes; and in the first place let us inquire what may be the cause of the light of the sun. Seeing, therefore, the body of the sun doth by its simple circular motion thrust away the ambient ethereal substance sometimes one way sometimes another, so that those parts, which are next the sun, being moved by it, do propagate that motion to the next remote parts, and these to the next, and so on continually; it must needs be that, notwithstanding any distance, the foremost part of the eye will at last be pressed; and by the pressure of that part, the motion will be propagated to the innermost part of the organ of sight, namely, to the heart; and from the reaction of the heart, there will proceed an endeavour back by the same way, ending in the endeavour outwards of the coat of the eye, called the retina. But this endeavour outwards, as has been defined in chapter [XXV], is the thing which is called light, or the phantasm of a lucid body. For it is by reason of this phantasm that an object is called lucid. Wherefore we have a possible cause of the light of the sun; which I undertook to find.
How light heateth.