Page:Popular Science Monthly Volume 33.djvu/271

Rh that the bright rays can be recognized on the bright part of the solar spectrum only by the difference of their brilliancy. On the other hand, we have not recognized the presence of the emission spectrum of carbon among the numerous bright rays observed in the spectrum of the solar atmosphere; and this fact goes to indicate the absence of carbon among the constituent elements of the sun. But such an assertion can not be made until our acquaintance with the subject becomes more complete and clear.

Although it is hardly possible, in the actual state of our knowledge, to establish the presence of carbon in the sun, it is extremely easy to recognize it in the spectra of comets. In 1868, when the comets of Winnecke and Brorsen appeared, Secchi in Italy, Huggins in England, and Wolf in France, studying the spectra of those stars in respect to their composition, discerned that the three bright bands, yellow, green, and blue, of which they were formed, could be regarded as analogous with the spectrum of carbon. It is possible, in fact, in a gas-light re-enforced by oxygen, if the brightness of the flame is reduced and a spectroscope of feeble dispersion is used, to obtain a spectrum exactly like that of a comet. After these observations, Mr. Christie and myself recognized the violet band in the spectrum of the comet h of 1881, and Dr. Young has found that the green band, or the most brilliant one in the spectrum of this comet, is formed of rays like the corresponding green band of the spectrum of flame. The identity of the two spectra is therefore demonstrated.

The presence of carbon is also suspected, if not definitely recognized, in the spectra of certain stars, the orange or red color of which indicates a temperature of relatively inferior elevation. The spectra of these stars consist of several dark bands, superposed upon a continuous bright spectrum, which present a great similarity of aspect and position with the luminous bands of the spectrum of carbon in comets, illuminating gas, and the candle flame. We have then, here, the absorption spectrum of carbon. The spectral analysis of the candle-flame thus permits us to discover by optical methods the presence of one of the most important elements of our globe in luminous bodies, whether celestial or terrestrial, whatever their distance, even though it be so great that light occupies thousands of years in coming to us.—Translated for the Popular Science Monthly from Ciel et Terre.

While generally accepting Mr. James Murray's views regarding the formation of barrier reefs and atolls, Mr. J. L. Wheaton would regard as the principal agent in forming the interior lagoons, not the solution and washing out of dead coral by sea-water, but privation of the inner part of the reef of food, all nourishment having been absorbed by the corals of the outer reef from the water before it reaches the interior.