cal sound or tone, is that which produces a continuous sensation, and of which one can appreciate the musical value. Noise is a sound of too short a duration to be appreciated well, as the noise of a cannon, or else it is a mixture of confused and discordant sounds like the rolling of thunder. For a single sound to become a musical sound, that is to say, a tone corresponding to one of the intonations of the musical scale, it is necessary that the impulse and, consequently, the undulations of the air should be exactly similar in duration and intensity, and that they should return after equal intervals of time. In its change to the musical state, however dull and confused the noise may be, it becomes clear and brilliant. Like the diamond, after having been polished and cut according to the rules of art, it has the brilliancy for the ear which the former has for the eye. This is what takes place in singing-flames. Very imperfect in its beginning, hoarse, roaring, or detonating, it does not come nearer the musical sound, properly so called in the chemical harmonica, as it is termed, still, by means of reiterated trials, the sound of the single flame in the tube, the lumen philosophicum, as it is elsewhere called, can it be musically produced in every case.
It has long been known that a flame traversing a glass tube under a certain pressure produces a musical sound. The eminent savant, Prof. Tyndall, to whom the greater part of the deep questions in physics are no mysteries, has studied singing-flames, but it must be admitted that singing-flames have only penetrated into the dominion of art in consequence of the discovery made by M. Frederick Kastner of the principle which allows of their being tuned and made to produce at will all the notes of the musical scale, to stop the sound instantaneously and mechanically; as in keyed instruments, the sound is regulated and subdued as desired. It is thus that the modest harmonica chimique, lumen philosophicum of natural philosophers has, in the pyrophone, attained to the character of a real musical instrument; this happy result supports the remark that the observation in Nature of the phenomenon of sound may conduct man, if not exactly to the invention of music, at least to endow the art with resources which increase its power. The sound of the pyrophone may truly be said to resemble the sound of a human voice, and the sound of the Æolian harp; at the same time sweet, powerful, full of taste, and brilliant; with much roundness, accuracy, and fullness; like a human and impassioned whisper, as an echo of the inward vibrations of the soul, something mysterious and indefinable; besides, in general, possessing a character of melancholy, which seems characteristic of all natural harmonies. The father of this young philosopher, a member of L'Institut de France, and a learned author, who died in 1867, treating on cosmic harmonies, insists on this peculiarity:
"The harmonies of Nature," said he, "which, in their terrible grandeur as well as in their ineffable sadness, have ever charmed the philosopher, poet, and
