NATUKAL PHILOSOPHY. 175 



in the free state. 1 The absence in the solar spectrum of the lines of 

 a particular metal does not prove the absence of the metal itself, since 

 it may exist in combination with some element, the compound itself 

 exhibiting no spectrum. The many new lines recently discovered in 

 the spectrum, and to which no elements are known to correspond, 

 may prove to be the lines of compounds of the first order of metals 

 already known. Pogg. Ann. cxvi. 499. 



Spectrum Analysis in Lecture Rooms. M. Debray, of Paris, has 

 successfully carried out the idea of projecting the spectra of flames 

 colored by the metallic elements upon a screen by means of a Drum- 

 mond light. The combustion of coal gas sustained by atmospheric 

 air gives too pale a flame when metallic substances are introduced 

 into it to enable us to see the spectra clearly except with the aid of 

 a telescope ; but if we take the exceedingly hot jet of an oxyhydro- 

 gen blow-pipe, colored by various metals, the splendor it acquires is 

 so brilliant that it becomes very easy to project the spectrum upon a 

 screen, so as to be seen distinctly by an audience. To this end, the 

 flame is introduced into Duboscq's photographic apparatus, now 

 so generally employed in optical experiments, and proceed precisely 

 as in obtaining the spectrum from an oil lamp, or from the voltaic 

 arc. We then obtain, upon a screen suitably adjusted, the series of 

 brilliant and van-colored rays which characterize the metal intro- 

 duced into the flame. These experiments are successful not only 

 with the alkaline and earthy alkaline metals, but also with other 

 metals, such as copper and lead, although these bodies give, with a 

 gas flame, and the ordinary apparatus, only a very confused phenom- 

 enon. As platinum melts instantaneously in the flame of the blow- 

 pipe, the metallic substance is introduced by means of the small piece 

 of retort-coke, or by a match strongly impregnated with the matter 

 to be experimented upon, which will be preferably selected from the 

 metallic chlorides. With a little practice we can sustain the phenom- 

 enon long enough to study all its details at a very great distance. 



Homoeopathic Medicines and the Spectroscope. Dr. Chas* Ozanam 

 states in the British Journal of Homoeopathy that a spectroscope by 

 Steinlieil enabled him to recognize lithium in the fifth dilution of 

 its chloruret, a drop containing five billionths of a milligramme. The 

 milligramme is one thousandth of one gramme, which is a minute frac- 

 tion, less than fifteen and one-half grains. He detected sodium in a 

 drop of the sixth dilution of its chloruret, which weighed three cen- 

 tigrammes, and contained three hundred. billionths of a milligramme. 



1 In regard to this conclusion of M.Mitscherlich,T)r Gibbs, in Silliman' > s 

 remarks "as follows : It does not appear to bo justified upon chemical considera- 

 tions, For it may be that the oxids, snlphids, chlorids, etc., of sodium aud pot- 

 assium are decomposed into their elements at the temperature of the sun's atmos- 

 phere, and consequently sodium, potassium, oxygen, sulphur, chlorine, etc., may 

 be coexistent in the free state in the sun's atmosphere, and there may be far more 

 than enough oxygen, etc., to combine with all the potassium and sodium. It 

 would be unsafe' to argue that 'because oxygen is the most abundant terrestrial, 

 it must also necessarily be the most abundant solar element, yet such is possibly 

 the case. Moreover, it is not necessarily true that all metals which arc reduced 

 from their compounds by sodium must exist in the suu'S atmosphere in a free 

 state, because the masses or absolute quantities, as well as the temperatures, must 

 be taken into consideration in judging of the affinities actually controlling com- 

 bination. 



Mitscherlich's experiments are certainly of great interest, and. in fact, form the 

 second great step in our know ledge of the constitution of the sun's atmosphere. 



