attributed to the absorption of the solar atmosphere; they were neither broader nor more numerous in the spectrum formed during that phenomenon than at any other time, though the rays came only from the circumference of the sun’s disc, and consequently had to traverse a greater depth of his atmosphere. Sir David Brewster found that in certain states of the atmosphere the obscure lines become much broader, and some of them deeply black; and he observed also, that, at the time the sun was setting in a veil of red light, part of the luminous spectrum was absorbed, whence he concluded that the earth’s atmosphere had absorbed the rays of light which occupied the dark bands. By direct experiments also the atmosphere was observed to act powerfully upon the rayless lines. When a lens is used along with a prism, longitudinal dark lines of different breadths are seen to cross the bands, already described, at right angles; these M. Ragona-Scina and M. Babinet believe to be lines of interference which exist in light that has passed through a convex lens. The lines are different both in kind and number in the spectra of gases and flames. In a highly-magnified spectrum from light passed through nitrous acid gas, Sir David Brewster counted 2000 dark bands. In the spectrum of a lamp, and generally of all white flames, none of the defective lines are found; so all such flames contain rays which do not exist in the light of the sun or stars. Brilliant red lines appear in the spectrum produced by the combustion of nitre upon charcoal; and in all artificial flames dark and bright bands exist, sometimes corresponding in position with those in the solar spectrum, and sometimes not.