[Transcriber's note: This discussion is impressive, considering that quantum theory and the internal structure of the atom appears many decades in the future.]
Translated From The Etudes Religieuses.
Recent Scientific Discoveries.
By Fr. Carbonelle.
The hypothesis of an ethereal medium everywhere diffused, is still, in spite of some vague objections urged against it, universally received, and the most recent theories and researches have not suggested its abandonment or modification in any important respect. On the contrary, they point to its more exact establishment, and to its application to large classes of phenomena in which, until lately, it was hardly supposed to be involved. There is no longer any branch of natural philosophy which can dispense with it; and in the theory of heat as a mode of motion, which will soon be the basis of a new system of physics more full and clear than the previous one, the motion must probably be explained by the principle of ethereal undulations or vibrations.
These vibrations show themselves by three different effects, namely, heat, chemical action, and color. The first two were for a long time neglected, but the third offered quite a large field, in which many very beautiful discoveries were made. It was known, for instance, that the oscillations were made with prodigious rapidity. Thus, the red of the spectrum is produced by vibrations repeated four hundred and eighty-three trillions of times in a second; while for the violet, more than seven hundred and eight trillions are required. Between these limits all the visible rays are contained, and, taken successively, they produce all the shades of the spectrum, and, by their combination, all possible colors. But as there are vibrations in the air too rapid or too slow to give the sense of sound to the ear, so there are, in the ether, slower than the red, or quicker than the violet, and hence invisible. The first have been detected by their calorific, the second by their chemical effects. The spectrum has thus been considerably extended at both ends, and we cannot be sure that its true limits have even yet been found.
These facts have been known for some time, and are found in all treatises on physics. We only speak of them in order to explain better the theories proposed by modern science to explain the three effects of ethereal radiation.
The hypothesis of three essentially different kinds of rays has now been abandoned. The solar beam, for example, which causes six hundred and thirty trillion vibrations a second, has the three properties of producing in the eye the sensation of blue, of heating Melloni's thermo-electric pile, and of decomposing the chloride of silver used in photography; but it does not appear that three different rays vibrating with this velocity are sent to us, each the cause of a separate effect. Notwithstanding the most careful experiments, no one of these properties has ever been diminished in a ray without diminishing the rest in the same proportion. Of course, these properties are differently proportioned in the different rays of the spectrum; but in two rays from the same part, and hence having the same velocity of vibration, these properties always consist in the same relative intensity. At the red end of the spectrum, the heating power predominates; at the other extremity, the chemical; in the middle, the luminous. The reason of this seems to be merely the difference of vibratory velocities; and we shall see that this will suffice to account for it.
Let us first explain how we conceive the production of the phenomena of chemical action and of heat. For clearness, we must advert to a theory familiar to all, according to which ponderable matter is composed of excessively small volumes, called atoms, which, though perhaps theoretically divisible, are never divided by any physical or chemical action. In the constitution of bodies, these atoms are supposed to be grouped in some manner, each group forming what is called a molecule. These, unlike the atoms, are decomposed in chemical changes, though not in physical ones, by which we understand such as evaporation, melting, crystallization, heating, magnetizing, electrifying, etc., unless these happen to affect the chemical constitution as well as the physical condition of the substance. All these do not alter the arrangement of the atoms in the molecule, but only the position or distance of the molecules with regard to each other. A collection of molecules may be called a particle; physical action then alters the constitution of the particle as chemical does that of the molecule. It may be remarked that our senses give us no direct evidence of the existence of molecules, much less of that of atoms, and they are supposed to be so extremely small that it will probably never be possible to detect them in this way.
In the application of this chemical theory to that of light, a new hypothesis is made, namely, that the ethereal fluid, whether itself continuous or composed of separate elements, penetrates all the interstices between the atoms of a molecule, as well as those between the molecules. The motions of this fluid, and of the matter which it penetrates, are communicated to each other, according to laws not yet ascertained, but of which we already have some glimpses. Thus, in treating of the effects of the ethereal vibrations on ponderable bodies, great importance is probably due to what is called isochronism, or equality of times; that is, the agreement of the rapidity of vibration of the ether with that of which the matter is susceptible; for in all known communications of vibratory movements, this isochronism plays a very notable part. If, for example, we place upon the same stand two clocks, having pendulums of the same length, and consequently swinging in the same time, and start one of them, the slight impulses communicated by this to the other will finally set the latter also in motion. If, on the other hand, the pendulums are not isochronous, no such effect will be produced. In the same way, a stretched cord will vibrate if one of the sounds of which it is capable is produced near by; but it will not be affected by other notes, even though much louder—showing that isochronism is more important than intensity. Another illustration of the same thing struck me forcibly some ten years ago. I had ascended with some photographic apparatus to the top of an old square tower, very high and massive, to take some views. The tower belonged to a church, the bells of which were rung several times while I was there. The great bell, though of a very considerable size, shook the building very slightly; it hardly caused any tremor in the image of the landscape. But a second and much smaller bell could not be rung without giving to the tower, after two or three minutes, a strong swaying movement like that of a tree shaken by the wind. This was owing to the isochronism between the oscillations of the tower and of the small bell, which more than compensated for the difference of mass.