.88 REPORT — 1861. 



the lines produced were those which were characteristic of the metal. The pecu- 

 liar lines of the metal seemed chiefly to be confined to the visible portion of the 

 spectrum, and these had little or no photographic power. This was singularly 

 exemplified by repeating the experiment upon the same metal in air, in a continu- 

 ous current o±" pure hydrogen. Iron, for example, gave, in hydrogen, a spectrum in 

 which a bright orange and a strong green band were visible, besides a few faint 

 lines in the blue part of the spectnim. ■ Although the light produced by the action 

 of the coil was allowed to Ml for ten minutes upon a .sensitive collodion surface, 

 scarcely a trace of any action was procured ; whilst, in five minutes, in the air, a 

 powerful impression of numerous bands was obtained. It was remarked by Mr. 

 Talbot that, m the spectra of coloured flames, the natiu-e of the acid did not influ- 

 ence the position of the bright lines of the spectrum, which he foimd was dependent 

 upon the metal employed ; and this remark has been confirmed by all subsequent 

 observers. But the case is very different in the absorption-bands produced by 

 the vapours of coloured bodies, — there the nature of both constituents of the com- 

 poimd is essentially connected with the production of absoi-ptive bands. Chlorine, 

 combined with hydrogen, gave no bands by absorption in any moderate thickness. 

 Chlorous acid and peroxide of chlorine both produced the same set of bands, while 

 hypochlorous acid, although a strongly coloured vapour and containing the same 

 elements, oxygen and chlorine, produced no absorption-bands. Again, the brown- 

 ish-red vapour of perchloride of iron produced no absorption-bands ; but when con- 

 verted into vapour in a flame, the iron showed bands independent of the form in 

 which it occurred combined. These anomalies appear to admit of .an easy expla- 

 nation on the supposition that, in any case, the compound employed is decomposed 

 in the flame, either simply by the high temperature, just as water is, as shown by 

 Grove, or in other cases by the reducmg action of the burning bodies, which supply 

 the flame, upon the metallic salt introduced into the flame. In the voltaic pile the 

 decomposition must of necessity take place by electric action. The compound gases, 



Erotoxide and binoxide of nitrogen, give, when electrified, the same series of bright 

 ands (as Plucker has sho%\Ti) which their constituents when combined furnish. 

 Aqueous vapour always gives the bright lines due to hydrogen ; and hydrochloric 

 acid the mixed system of lines which would be produced by hydrogen and chlorine. 

 The reducing influence of the hydrogen and other combustible constituents of the 

 burning body woidd decompose the salt, liberating the metal, which would imme- 

 diately become oxidized or earned off in the ascending current. There was obvi- 

 ously a marked difference between the effect of intense ignition upon most of the 

 metallic and the non-metallic bodies. The observations of Pliicker upon the spectra 

 of iodine, bromine, and chlorine show that they give, when ignited, a very different 

 series of bands from those which they furnished by absoi-ption, as Dr. Gladstone has 

 already pointed out ; but it is interesting to remark that in the case of hydrogen, 

 which, chemically, is so similar to a metal, we have a comparatively simple spec- 

 trum, in which the three principal bright lines correspond to Frarmhofer's dark 

 lines C, F, and G. It was, however, to be specially noted that the hydrogen occa- 

 sioned no perceptible absoiiition-bands at ordinaiy temperatures in such thickness 

 as we could command in our experiments, and the vapoiu- of boiling mercury was 

 also destitute of any absoi-ptive action, although, when ignited by the electric spark, 

 it gave a characteristic and brilliant series of dark bands. The following experi- 

 ment suggested itself as a direct test of Kirchhofii''s theory. Two gas-burners, into 

 which were introduced chloride of sodium on the wick of the spirit-lamp, were 

 placed so as to illuminate equally the opposite sides of a sheet of paper partially 

 greased. The rays of the electric light screened from the photometric surface, suit- 

 ably protected, were made to traverse one of the flames. If the yellow rays of the 

 light were absorbed by the sodium flame, the light emitted laterally by the flame 

 shoidd be sensibly increased. The experiment, however, failed to indicate any 

 such increase in the brilliancy of the flame, possibly because the eye was not suf- 

 ficiently sensitive to detect the slight difference which was to be expected. 



On Atmosplieric Ozone. By Dr, MorPAT. 



The results given were from the observations of ten j-ears, taken at Ilawarden at 

 a height of 260 feet above the level of the sea. The quantity of ozone is greater with 



