562 PRINCIPLES OF CHEMISTRY 



that degree of heat which is proper to the sun those simple matters 

 which we accept as the elements in chemistry are still undeconiposed 



of the calcium spectrum, at comparatively low temperatures, whilst the lines 397 and 

 893 appear at a higher temperature, and at a still higher temperature the line 423- 

 becomes quite invisible. 



Lockyer, to whom spectroscopy is indebted for many excellent spectroscopic observa- 

 tions, supposes that the elements existing on the earth are decomposed at the tempera- 

 ture of the sun for instance, that iron decomposes into two new elements having par- 

 ticular spectra, because an unequal intensity of all the lines of iron is observed in dif- 

 ferent portions of the sun (spots, prominences, &c.), and because a displacement (Note 

 34) of certain of the lines of this metal may be observed in the sun's spots at the same 

 time that other lines remain undisplaced. Lockyer supposes this to depend on the 

 movement of one component part of iron with an immobility of the position (in space) of 

 the other product of the decomposition of iron which remains in a lower stratum. Prof. 

 Kleiber explains these phenomena by the fact that the visible spectrum of the sun is 

 determined by the entire thickness of the atmosphere of the sun, by the inequality of the 

 movement of different strata of the sun's atmosphere, and by the fact that lines of dif- 

 ferent wave lengths offer a different constant with reference to Kirchhoff's law. It is 

 enough if the thickness, pressure, and temperature of an incandescent vapour be dif- 

 ferent in a laboratory experiment and in a given stratum of the solar atmosphere to 

 obtain a marked difference in the intensity of the light of different bands of the spectrum 

 of one and the same element. As regards the displacement of only one portion of the 

 iron lines, Kleiber supplements Liveing and Dewar's observation that the displaced lines 

 are those emitted by the most rarefied vapours (Note 27), by pointing out that in the 

 first place one and the same line is sometimes observed on the sun both in a contorted 

 (broken) and normal position (as Lockyer himself observe!), and in the second place that 

 the intensity of the light of different lines depends on the different temperatures and den- 

 sities of the strata of the solar atmosphere, and therefore the lines determined by the 

 upper strata may, by their movement, be displaced, whilst the other lines determined by 

 the lower strata may remain unchanged. Besides which I may observe, for my part, 

 that if, under ordinary conditions, we see the normal spectrum of iron in the sun, Lock- 

 yer's supposed component parts of iron must occur together in the sun, and therefore it 

 is difficult to understand how one component part of iron is able to move whilst the 

 other remains at rest. Furthermore, as the solar spectrum of iron entirely corresponds 

 with that obtained by experiment at the comparatively low temperatures obtainable in 

 the laboratory, it is necessary to admit one of the two following propositions either 

 the decomposition of iron does not require so high a temperature as that on the sun, and 

 then it would be easy to prove this supposed complexity of iron by a laboratory experi- 

 ment, or it must be admitted that the two component parts of iron when combined to- 

 gether (forming undecomposed iron) do not alter the positions of their spectral lines, 

 whilst, as we shall see later, the spectra of elements change when they combine together, 

 and therefore that in the case of iron a proposition must be made contradictory to this 

 fact. Other data put forward by Lockyer in favour of the decomposability of certain 

 elements proved when re-investigated (by Liveing and Dewar), by means of spectroscopes 

 of high dispersive power, to be only founded on the confusion of dissimilar lines. The 

 arguments of Lockyer concerning the decomposability of elements, which at one time 

 made a great impression, do not thus appear to support the doctrine of a single common 

 material (p. 20, Note 26), but must be made use of for the further development of spec- 

 troscopic science. Besides which I consider it well to turn attention to the facts (1) that the 

 conception of the elements stands in all respects more firmly than any deductions obtained 

 by the spectroscope; (2) this comparatively young doctrine of the spectra of elements is 

 only the fruit of the chemical doctrine of elements; and (3) that as yet no generalisa- 

 tions, besides Kirchhoff's law, have appeared for spectroscopic phenomena, which could 

 allow predictions being made, whilst the conception of elements has already arrived at 

 this stage. When, however, spectroscopic science has been developed to the same extent 



