534 



THE POPULAR SCIENCE MONTHLY. 



compounding and recompounding ; just 

 as by the compounding and recom- 

 pounding of so-called elements there 

 arise oxides and acids and salts." 



Mr. Lockjer aims to enforce these 

 views by fresh i' lustrations. The fol- 

 lowing passages from an account of his 

 paper written for the " London Times," 

 by a chemist who heard it, will give a 

 fair idea of its quality : 



There are many facts and many trains of 

 thought suggested by solar and stellar phys- 

 ics which point to the hypothesis that the 

 elements themselves, or at all events some 

 of them, are compound bodies. Thus it 

 would appear that the hotter a star the more 

 simple IS its spectrum ; for the brightest, 

 and therefore probably the hottest stars, 

 such as Sirius, furnish spectra showing only 

 very thiclc hydrogen hnes and a few very 

 thin metallic hnes, characteristic of elements 

 of low atomic weight, while the cooler stars, 

 such as our sun, are shown by their spectra 

 to contain a much larger number of metallic 

 elements than stars such as Sirius, but no 

 non-metallic elements ; and the coolest 

 stars furnish fluted band-spectra character- 

 istic of compouuds of metallic with non- 

 metallic elements and of non-metallic ele- 

 ments. These facts appear to meet with a 

 simple explanation if it be supposed that as 

 the temperature increases the compounds 

 are first broken up into their constituent 

 '"elements," and that these "elements" 

 then undergo dissociation or decomposition 

 into "elements" of lower atomic weight. 

 Mr. Lockyer next considers what will be the 

 difference in the spectroscopic phenomena, 

 supposing that A contains B as an impurity 

 and as a constituent. In both cases A will 

 have a spectrum of its own. B, however, if 

 present as an impurity, will merely add its 

 lines according to the amount present, as we 

 have above explained ; whereas if a constit- 

 uent of A it will add its lines according to 

 the extent to which A is decomposed and B 

 is set at liberty. So that as the temperature 

 increases the spectnira of A will fade if A 

 be a compound body, whereas it will not 

 fade if A be a true element. Moreover, if 

 A be a compound body, the longest lines at 

 one temperature will not be the longest at 

 another. The paper chiefly deals with a 

 discussion from this point of view of the 

 spectrum of calcium, iron, hydrogen, and 

 lithium, as observed at various tempera- 

 tures ; and it is shown that precisely the 

 kind of change which is to be expected on 

 the hypothesis of the non-elementary char- 



acter of the elements has been found to take 

 place. Thus each of the salts of calcium, 

 so long as the temperature is below a certain 

 point, has a definite spectrum of its own, 

 but as the temperature is raised the spec- 

 trum of the salt gradually dies out and very 

 fine lines due to the metal appear in the blue 

 and violet portions of the spectrum. At the 

 temperature of the electric arc the line in 

 the blue is of great intensity, the violet H 

 and K lines, as they are called, being still 

 thin ; in the sun the H and K lines are very 

 thick, and the line in the blue is of less in- 

 tensity than either, and much thinner than 

 in the arc. Lastly, Dr. Huggins's magnifi- 

 cent star photographs show that both the H 

 and K lines are present in the spectrum of 

 a. Aquilce, the latter' being, however, only 

 about half the breadth of the former ; 

 but that in the spectrum of o Lyrae 

 and Sirius, only the H line of calcium is 

 present. Similar evidence that these differ- 

 ent lines may represent difi"erent substances 

 appears to be afibrded by Professor Young's 

 spectroscopic observations of solar storms, 

 he having seen the H line injected into the 

 chromosphere Eevent3'-flve times, the K line 

 fifty times ; but the blue line, which is the 

 all-important line of calcium at the arc tem- 

 perature, was only injected thrice. In the 

 spectrum of iron two sets of three lines oc- 

 cur in the region between H and G, which 

 are highly characteristic of this metal. On 

 comparing photographs of the solar spec- 

 trum and of the spark taken between poles 

 of iron, the relative intensity of these trip- 

 lets is seen to be absolutely reversed ; the 

 lines barely visible in the spark photograph 

 being among the most prominent in that of 

 the solar spectrum, while the triplet, which 

 is prominent in the spark photograph, is rep- 

 resented by lines not half so thick in the so- 

 lar spectrum. Professor Young has observed 

 during solar storms two very faint hnes in 

 the iron spectrum near G injected thirty 

 times into the chromosphere, while one of 

 the lines of the triplet was only injected 

 twice. These facts, Mr. Lockyer contends, 

 at once meet with a simple explanation if it 

 be admitted that the lines are produced by 

 the vibration of several distinct molecules. 



The lithium spectrum exhibits a series 

 of changes with a rise of temperature pre- 

 cisely analogous to those observed in the 

 case of calcium. 



In discussing the hydrogen spectrum, 

 Mr. Lockyer adduces a number of most im- 

 portant and interesting facts and specula- 

 tions. It is pointed out that the most 

 refrangible line of hydrogen in the solar 

 spectrum, 7t, is only seen in laboratory ex- 



