Chloride of lithium gives the red and orange lines on its spectrum; the brilliant blue band discovered by Mr. Tyndall, and another more refrangible blue line is seen when the ignition is at its greatest intensity. Chloride of calcium gives a blue band very brightly, and several other lines. The light of the chloride of copper is very vivid, and its spectrum is remarkable for changing its appearance with the decomposition of the chloride. The chlorides of lead and cadmium, also, give very bright and definite spectra, and chloride of bismuth shows numerous brilliant red and blue rays which quickly disappear. Thus the chlorides give spectra with lines, such as the blue lithium and strontium lines, hitherto only brought out by an intense electric spark.[19] M. Bunsen produced a beautiful effect by vaporizing a mixture of equal parts of the chlorides of sodium, potassium, lithium, calcium, strontium, and barium, and passing the light through the slit of his apparatus. For on looking through the telescope the spectrum of each substance with its characteristic coloured lines in all their brilliancy came successively into view, and gradually faded away as each substance was volatilized and driven off. The sequence showed the time required to vaporize each metal, and by spectrum analysis each metal could be recognized, although the mixture only contained the 1/1000 part of a grain of each chloride. The position, colour, and nature of the bright lines on the spectra of more than thirty metals have been determined, besides those of the elementary gases and that of the electric spark. To these M. Louis Grandeau has added the spectrum of lightning. By a particular arrangement the light passed at once through the slit in the instrument, and a glass tube containing nitrogen and the vapour of water. The general appearance of the lightning spectrum at first recalled that of the electric spark, but on a closer examination, M. Grandeau noticed in the spectrum of almost every flash the coincidence of a certain number of the rays of the lightning spectrum with those of the spectra of nitrogen and hydrogen. M. Grandeau remarks that this result is not surprising, since all admit the production of ammonia and nitric acid under the influence of electrical discharges. Besides the rays of nitrogen and hydrogen, the lightning spectrum contains the ubiquitous yellow ray of sodium.