Jan. 9, 1879] 



NATURE 



225 



DISCUSSION OF THE WORKING HYPOTHESIS 

 THAT THE SO-CALLED ELEMENTS ARE 

 COMPOUND BODIES^ 

 II. 



Application of the above Views to Calcium, Iron, Lithium, 

 and Hydrogen 



Calciinn 



T was in a communication to the Royal Society made 

 now some time ago {Proc.,\o\. xxii, p. 380, 1874), that 

 I first referred to the possibihty that the well-known Hne- 

 spectra of the elementary bodies might not result from 

 the vibration of similar molecules. I was led to make 

 the remark in consequence of the differences to which 

 I have already drawn attention in the spectra of certain 

 elements as observed in the spectrum of the sun and 

 in those obtained with the ordinary instnmaental ap- 

 pliances. 



Later {Proc. Roy. Soc, No. 168, 1876) I produced 

 evidence that the molecular grouping of calcium which, 



I 



with a small induction-coil and small jar, gives a spectrum 

 with its chief Une in the blue, is nearly broken up in 

 the sun, and quite broken up in the discharge from a 

 large coil and jar, into another or others with lines in the 

 violet. 



I said "another," or "others," because I was not therk 

 able to determine whether the last-named lines proceeded 

 from the same or different molecules ; and I added that it 

 was possible we might have to wait for photographs of 

 the spectra of the brighter stars before this point could 

 be determined. 



I also remarked that this result enabled us to fix- 

 with yer>' considerable accuracy the electric dissociating 

 conditions which are equivalent to that degree of disso- 

 ciation at present at v.ork in the sim. 



In Fig. 3 I have collected several spectra copied from 

 photographs in order that the line of argiunent may be 

 grasped. 



First we see what happens to the non-dissociated and 

 the dissociated chloride. Next we have the lines with 

 a weak voltaic arc, the single line to the right (W L. 



Fig. 3. — The blue end of the spectrum or caicum uncer differeDt conditions, i. Calcium is comKned with chlorine (CaCl^). When the temperatiire is- 

 low, the compound molecule vibrates as a whole, the spectrum is at the red end, and no lines of calcium are seen. 2. The line of the metal seen 

 when the compound molecule is dissociated to a slight extent with an induced current. 3. The spectrum of metallic calcium in the electric arc 

 with a small number of cells. 4. The same when the number of cells is increased s- The spectrum when a coil and small jar are employed. 

 6. The spectrum when a large coil and large jar are used. 7. The absorption of the calcium vapour in the Sun. 



4226'3) is much thicker than the two lines (W L 3933 and 

 3968) to the left, and reverses itself. 



We have next calcium exposed to a current of higher 

 tension. It will be seen that here the three lines are 

 almost equally thick, and all reverse themselves. 



Now it will be recollected, that in the case of knoun 

 compounds the band structure of the true compounds is 

 reduced as dissociation works its way, and the spectrum 

 of each constituent element makes its appearance. If 

 in 3 we take the wide line as representing the banded 

 spectrum of the compound, and the thinner ones as 

 representing the longest elemental lines making their 

 appearance as the result of partial dissociation, we have, 

 by hypothesis, an element behaving like a compound. 



If the hypothesis be true, we ought to be able not only 

 to obtain, with lower temperatures, a still greater prepon- 

 derance of the single line, as we do; but with higher 

 temperatures, a still greater preponderance of the double 

 ones, as we do. 



I tested this in the following manner : — Employing 



' Paper read at the Royal Society, December 12. 1878, by T. Norman 

 Lockyer. F.R.S. Continned from p. 201. 



photography, because the visibility of the more refrangi- 

 ble lines is small, and because a permanent record of ark 

 experiment, free as it must be from aU bias, is a very 

 precious thing. 



Induced currents of electricity were employed in order 

 that all the photographic results might be comparable. 



To represent tihe lowest temperature I used a small 

 induction coil and a Leyden jar only just large enough to- 

 secure the requisite amount of photographic effect. To- 

 represent the highest, I used the largest coil and jar at 

 my disposal. The spark was then taken between two alu- 

 minium electrodes, the lower one cup-shaped, and charged 

 with a salt of calcium. 



In the figure I give exact copies of the results obtained. 

 It will be seen that with the lowest temperature only the 

 single line (2) and with the highest temperature only the 

 two more refrangible lines (6) are recorded on the plate. 



This proved that the intensity of the vibrations was 

 quite changed in the two experiments. 



Perhaps it may not be superfluous here to state the 

 reasons which induced me to search for fiirther evidence 

 in the stars. 



