Photographic Spectra of Stars to the 3i Magnitude. 213 



we do not witness in these stars the original formation of our 

 elements ; for his own theory supposes the stars to be formed from 

 condensing matter originally cool, in which the metals, as we know 

 them, are already present. What we see in these stars, as I under- 

 stand his theory, is a case of atavism, a temporary relapse of our 

 elements into their original state. That may be so. It is in my 

 opinion as I have already stated, a perfectly legitimate hypothesis, 

 one that at present has not been disproved, and for which, as well as 

 against which, a good deal might be said, but I cannot admit the 

 claim, that it is demonstrated. ISTor do I believe that it will be 

 generally accepted until some direct experimental evidence is 

 obtained. The resources of our laboratories are not yet exhausted ; and 

 we have not arrived at the limit to which we can push the intensity 

 of our electric sparks. If Mr. Lockyer is right we must look for- 

 ward to finding some trace of helium, or calcium, or hydrogen in the 

 discharge taken from iron poles. When that is done, and not till 

 then, will this theory be considered as proved. 



Additional Remarks by Mr. J. Norman Lockyer. 



Mr. Lockyer, in his reply, pointed out that it was not open to him 

 to discuss the question of classification. He had been asked to 

 prepare a paper on another subject, for the proper consideration of 

 which the question of classification had to be referred to. If Pro- 

 fessor Schuster, as he says he does, concurs generally in Mr. Lockyer's 

 scheme of classification, he must acknowledge that there must be a 

 very great difference in the amount of " stirring " on the two sides 

 of the temperature curve, and that powerful convection currents 

 must exist in the hotter stars in which the temperature is rising ; and 

 yet as a matter of fact the line absorption is very similar in both 

 arms of the curve. 



Mr. Lockyer has nowhere claimed that his hypothesis is the only 

 one which can explain the facts, he only claims that it is simple and 

 sufficient. 



Note by Mr. Frank MoClean, F.R.S., " On Comparative 

 Photographic Spectra of Stars to the 3^ Magnitude." 



The 160 photographs which accompany the paper* include, with 

 insignificant exceptions, all stars equal to and brighter than the 3| 

 magnitude contained in five out of eight equal areas, into which the 

 celestial sphere has been divided. 



* The paper to which reference is made, and on which Mr. McClean's remarks 

 were based, was read subsequently, at the meeting of April 8. 



