740 Prof. H. E. AfMnstrong on Low-Temperature Research 



Spectroscopic High Temperature Studies. 



During the later seventies and several years afterwards many 

 investigations were carried out, chiefly spectroscopic, to determine 

 the behaviour of substances at high temperatures, so that the data 

 might be obtained for the interpretation of the observations made by 

 astronomers. In those days speculation was rife as to the nature of 

 the elements ; over and over again it was asserted that evidence had 

 been obtained that they underwent dissociation — that is to say, rever- 

 sible decomposition — at the transcendental temperatures prevailing in 

 the sun and very hot stars. A variety of investigations were under- 

 taken by Prof. Dewar in conjunction with Prof. Liveing, partly in 

 the Institution laboratory and partly at Cambridge. The observa- 

 tions were of special value at the time on account of the fact that 

 they were carried out with the most scrupulous care by men alive to 

 the pitfalls which such work presents and always unwilling to draw 

 conclusions until the facts were rigidly established. 



Fortunately, the work of the two inquirers has been brought 

 together in a volume of "Spectroscopic; Studies," issued late in 1915 

 by the Cambridge University Press ; unfortunately, no new comments 

 are offered upon the papers (78) and no attempt is made to discuss 

 the general bearing of the results in the light of modern discoveries ; 

 this is the more to be regretted, as the authors too often allow their 

 observations to speak for themselves and refrain from all comment. 



Such inquiry has almost lost interest for the present generation ; 

 the acuteness of the controversy which arose forty years or so ago 

 is no longer realized, excepting by the few who watched the storm 

 rage. Taken in conjunction with that of Huggins in particular, the 

 work goes to show that however probable the view may be that the so- 

 called elements may undergo decompositions at high temperatures, the 

 evidence adduced could not be accepted as proof that such is the case. 



The subject of " Spectroscopic Investigation " was first brought 

 under notice by Prof. Dewar at a Friday evening, on June 6, 1879, 

 in a lecture which was a summary of communications to the Royal 

 Society during 1878-79 by Prof. Liveing and himself. This and 

 other lectures involving the use of the spectroscope, which he gave at 

 that period, will be remembered by all who were present, on account 

 of the many brilliant and most beautiful demonstrations whereby 

 phenomena were made visible to a large audience which, previously, 

 only single observers had been in a position to witness. They were 

 delivered at a time when the dynamo-electric machine was first coming 

 into favour in place of the troublesome 50-cell Grove battery pre- 

 viously employed in giving lecture demonstrations ; the systematic 

 use of the electric-arc lamp in the lecture room was largely due 

 to the example then set at the Institution, I believe. 



The subject dealt with was that of the reversal of Hues in the 



