NATURE 



309 



THURSDAY, AUGUST, 5, 18S0 



MULTIPLE SPECTRA^ 

 II. 



I CONCLUDED my last article under the above 

 heading with a reference to the case of carbon, and 

 gave the results successively arrived at by Attfield, 

 Morren, Watts, and others, which went to show that 

 besides the line-spectrum of carbon mapped by Angstrom 

 there exists a fluted spectrum of this substance. 



Now comes my own personal connection with this 

 matter. 



In the year 1S7S- I communicated to the Royal Society 

 a paper in which the conclusion was drawn that the 

 vapour of carbon was present in the solar atmosphere. 



This conclusion was founded upon the reversal in the 

 solar spectrum of a set of flutings in the ultra-violet. ^ The 

 conclusion that these flutings were due to the vapour of 

 carbon, and not to any compound of carbon, was founded 

 upon experiments similar to those employed in the 

 researches of Attfield and Watts, who showed that the 

 other almost e.xactly similar sets of flutings in the visible 

 part of the spectrum w-ere seen when several different 

 compounds of carbon were exposed to the action of heat 

 and electricity. In my photographs the ultra-violet flutings 

 appeared under conditions in which carbon was the only 

 constant, and it seemed therefore reasonable to assume 

 that the flutings were due to carbon itself, and not to any 

 compound of carbon; and this not alone from the previous 

 work done in the special case of carbon, but from that 

 which had shown that the fluted spectra of sulphur, 

 nitrogen, and so forth were really due to these "ele- 

 mentary " substances. 



Professors Liveing and Dewar have recently on several 

 occasions called this result in question. Prof. Dewar, 

 in a paper received by the Royal Society on January 8, 

 1S80, wTites as follows : — 



"The almost impossible problem of eliminating hydrogen 

 from masses of carbon, such as can be employed in experi- 

 ments of this kind, prove conclusively that the inference 

 drawn by Mr. Lockyer, as to the elementai-y character of 

 the so-called carbon spectrum from an examination of 

 the arc in dry chlorine, cannot be regarded as satisfactory, 

 seeing that jindo7tbtedly hydf-ogen was p>-esenf zh the carboii 

 used as the poles.'' 



Subsequently in a paper received by the Royal Society 

 on February 2, Messrs. Liveing and Dewar wrote as 

 follows : — 



"Mr. Lockyer (Proc. Roy. Soc, vol. .xxvii. p. 30S) has 

 recently * obtained a photograph of the arc in chlorine, 

 which shows the series of fluted bands in the ultra-violet, 

 on the strength of which he throws over the conclusion 

 of Angstrom and Thalen, and draws inferences as to the 

 existence of carbon vapour above the cliromosphere^ in 

 the coronal atmosphere of the sun, which, if true, would 

 be contrary to all we know of the properties of carbon. 

 We cannot help thinking that these bands luere due to the 

 presence of a small quantity of nitrogen." 



It will be seen that on January 8 Mr. Dewar alone 

 attributed the flutings to a hydrocarbon, while on February 

 2 Mr. Dewar, associated with Mr. Liveing, attributed 

 them to a nitrocarbon. 



. ' Continued from p. 7. = Proc. R. S., No. 1S7, 1S78. 



3 The approximate wave-length of the brightest, member on_the least 

 refrangible edge is sSSfo. ■• That is, in 1878.— J. N. L. 



'■ ' : : . - No. 562 



In fact in the latter paper Messrs. Liveing and Dewar 

 published experiments on the spectra of various carbon 

 compounds, and from their observations they have drawn 

 the conclusion that the set of flutings which I have shown 

 to be reversed in the solar spectrum is really due to 

 cyanogen, and that certain other sets of flutings shown 

 by Attfield and Watts to be due to carbon are really due 

 to hydrocarbon. 



As Messrs. Liveing and Dewar do not controvert 

 the very definite conclusions arrived at by Attfield, 

 Morren, Watts, and others, I can only presume that 

 they took for granted that aU the experimental work 

 performed by these men of science was tainted by the 

 presence of impurities, and that it was impossible to 

 avoid them. I therefore thought it desirable to go over 

 the ground again, modifying the experimental method so 

 as to demonstrate the absence of impurities. Indeed I 

 have started upon a research which will require some 

 time to complete. Still, in the meantime, I have sub- 

 mitted to the notice of the Royal Society some results 

 which I have obtained, which I think settle the whole 

 question, and it is the more important to settle it as 

 Messrs. Liveing and Dewar have already based upon 

 their conclusions theoretical views which appear to me 

 likely to mislead, and which I consider to have long been 

 shown to be erroneous. To these results I shall now 

 refer in this place. 



The tube with which I have experimented is shown 

 in Fig. I : A and B are platinum wires for passing the 

 spark inside the tube ; e is a small tube into which carbon 

 tetrachloride was introduced ; it was drawn out to a long 

 narrow orifice to prevent the rapid evaporation of the 

 liquid during the exhaustion of the tube. The tube was 

 bent upwards and a bulb blown at C in order that the 

 spark might be examined with the tube end-on, as it is 

 found that alter the spark has passed for som.e time a 

 deposit is formed on the sides of the bulb immediately 

 surrounding the platinums, thus obstructing the light. 

 After a vacuum had been obtained the tube was allowed 

 to remain on the Sprengel pump, to which it was attached 

 by a mercury joint for the purpose of obtaining a vacuum 

 for a long time, in order that the last traces of air and 

 moisture might be expelled by the slow evaporation of the 

 licjuid. 



The carbon tetrachloride was prepare^i by Dr. Hodg- 

 kinson, who veiy kindly supplied me with sufficient for 

 my experiments. 



On passing the spark without the jar in this tube, 

 the spectrum observed consists of those sets of flutings 

 which, according to Messrs. Liveing and Dewar, are due 

 to hydrocarbon, and the set of flutings which is reversed 

 in the sun, and ascribed by Messrs. Liveing and Dewar 

 to cyanogen, also appears in a photograph of the violet end 

 of the spectrum. Fig. 2. On connecting a Leyden jar with 

 the coil and then passing the spark the flutings almost 

 entirely vanish and the line spectra of chlorine and carbon 

 take the place of the flutings without either a line of 

 hydrogen or a line of nitrogen being visible. 



As a long experience has taught me that these tubes 

 often leak slightly at the platinums after they are detached 

 from the pump, so that the evidence of such b. piice jt/sti- 

 ficatif is only good for a short time, I took the occasion 

 afforded by a visit of Dr. Schuster to my laboratory while 



