So far Mr. Tyndall's experiments agree perfectly with the theory; they confirm it, but they do not extend it. He has, however, made others, which seem to disclose new points in the theory of exchange of movements between the ether and ponderable matter. It might no longer be the atoms or the molecules which would have to be considered in respect to the ethereal vibrations, but even the particles, if sufficiently small. In fact, these particles reflect the rays not absorbed, according to entirely new laws. In the first place, although belonging to colorless liquids, they reflect the blue rays much better than the others. This is true of all the vapors tried, without exception. This elective reflection only holds when their dimensions are small, since it disappears as the size of the particles increases. This is quite a new fact, and, it must be acknowledged, as yet quite unexplained. Secondly, they polarize light according to laws which must also be called new, being entirely different from those given by theory and experiment for polarization by reflection. In one respect these laws are not new; for they have been long observed in atmospheric polarization; but this has always been one of the knotty points of the undulatory theory. Evidently, Mr. Tyndall's experiments do not clear it up entirely; but they have made an important advance in that direction, by showing to what physical circumstance this polarization is probably due. It would appear, that is, that in the higher regions of our atmosphere there are vapors which, instead of condensing in particles large enough to form ordinary clouds, are precipitated like those used by Mr. Tyndall, and fill the air with extremely small particles and with incipient clouds. This hypothesis is certainly very probable. It accounts at once for the blueness of the sky, and for its polarization of light.
Here is, then, a problem for theorists, in a better condition than previously. We hope to return to it shortly, in a subsequent bulletin. In conclusion, let us point out a new application of these experiments to the physical theory of comets. Mr. Tyndall considers the cometary matter to be a vapor on which the sun's rays act physically and chemically. These two actions would be somewhat contrary to each other; for the first would tend to evaporate the liquid particles and expand the vapor, while the second would precipitate this vapor in the form of incipient cloud. As the comet approaches solar action, forming an immense volume, of which the visible part will be only a small fraction, the head being the most condensed portion. If, now, we suppose the head to absorb the heating rays more abundantly than the remaining ones, in the cool shadow behind it the chemical action may prevail, and form an incipient cloud, which will be the tail of the comet. Elsewhere, the calorific action will predominate, and the vapor will remain invisible. Such is substantially the new theory of comets. It certainly satisfies the general conditions of the problem, and especially it explains very naturally the enormously rapid movements observed in the tails of these bodies. But will what is still undetermined in it enable it to be accommodated to the numerous facts already observed, and hereafter to be so? Here, also, it may be regretted that the spectroscope was not employed by the English physicist. The spectra of the incipient clouds might have been compared with those of comets' tails; and would have given an excellent test of the theory. Perhaps, however, he has reserved this part of his researches for a future publication.
St. Oren's Priory.
Or, Extracts From The Note-book Of An American In A French Monastery.
"Pour chercher mieux."
—Device of Queen Christina of Sweden.
PART I.
"I hear a voice you cannot hear,
Forbidding me to stay:
I see a hand you cannot see,
Which beckons me away."
Such were the words on my lips, my dear friend, when I bade you farewell and promised that I would, from time to time, give you a picture of my convent life, that you might in spirit follow me closely into the sealed garden of the Beloved, though forced by circumstances to remain far from me in body.