148 INORGANIC EVOLUTION. [CHAP. 



plain the increased intensity of the lines of hydrogen, but the appear- 

 ance of the enhanced lines of iron as absorption lines. Now these 

 enhanced lines are already in the sun's chromosphere, and are pre- 

 sumably absent from the Fraunhofer spectrum, because the vapour 

 producing them approaches the temperature of the photosphere. Is it 

 possible that a state of quiescence in the sun would so increase the 

 temperature of the photosphere as to make visible the absorption of 

 these high temperature vapours ? And, if this be possible, there would 

 still be no apparent reason for the disappearance of the cool Jines of 

 iron. The change, however, from y Lyrae is readily explained if we 

 grant that there is an increase of temperature, producing proto-iron 

 from the previously cool iron vapour, and a dissociation capable of 

 producing the observed increase of hydrogen absorption at the expense 

 of proto-iron. 



How the increased absorption of hydrogen can be accounted for 

 otherwise is not clear. The idea of hydrogen being set free for this 

 purpose from beneath the photosphere does not seem to me probable. 



The final discussion of such subjects as these is very difficult, 

 because we learn from the sun that the absorption recorded is onl} r 

 that of a middle region. Neither helium nor coronium writes its 

 record among the Fraunhofer lines. Surely everybody will agree that 

 there are hundreds of substances in the higher cooler reaches of the 

 solar atmosphere which write no record. How then can we say that 

 under the conditions assumed by Dr. Schuster " there can be no doubt* 

 whatever that the low temperature lines of iron would make their 

 appearance." 



Dr. Schuster also refers to hydrogen " imprisoned beneath the 

 photosphere " ; is there any justification for this view ? The complete 

 history of hydrogen, including proto-hydrogen in stellar atmospheres, 

 is simply and sufficiently explained on the dissociation hypothesis. I 

 question whether an explanation which requires such an imprisonment 

 of hydrogen is more satisfactory. 



I now proceed to give another quotation from Dr. Schuster : 



" There is especially one question which Professor Lockyer must be 

 prepared to answer. Amongst the heavier metals, tellurium, anti- 

 mony, mercury, are not represented in the sun, but they are found in 

 Aldebaran. To be consistent, we must, if we adopt the theory of dis- 

 sociation, assert that these metals are decomposed in the sun. But, if 

 I understand Professor Lockyer right, he believes that with our 

 strongest sparks we can exceed the state of dissociation which exists 

 in the reversing layer of the sun. Take such a strong spark, then, 

 from a pole of mercury, do you get lines of helium, or of calcium, or 

 * The italics are mine. X, L. 



