22 S. P. Langley — The History of a Doctrine. 



And here I might end, hoping that there may be some les- 

 sons for us in the history of what has bee^~ said. I will ven- 

 ture to ask attention to but one. It is that in these days, when 

 the advantage of organization is so fully recognized, when 

 there is a well-founded hope that by cooperation among scien- 

 tific men knowledge may be more rapidly increased, and when 

 not only in the great scientific departments of government but 

 everywhere, there is a tendency to the formation of the divis- 

 ions of a sort of scientific army, not to say of a scientific 

 church — that at such a time we should yet remember, that, 

 however rapidly science changes, human nature remains much 

 the same ; and (while we are uttering truisms) let us venture 

 to repeat that there is a very great deal of this " human nature" 

 even in the scientific man, whose best type is one nearly as 

 independent as nature itself, and one which will not always 

 work best at the word of command. Let him then never for- 

 get that the history of science, scarcely less than of theology, 

 warns him of the tendency of authority to exceed its proper 

 sphere, and from without it, to define belief, and to impose 

 obedience to doctrine. 



Finally, if, turning to the future, I were asked what I 

 thought were the next great steps to be taken in the study of 

 radiant heat, I should feel unwilling to attempt to look more 

 than a very little way in advance. Immediately before us, 

 however, there is one great problem waiting solution. I mean 

 the relation between temperature and radiation ; for we know 

 almost nothing of this, where knowledge would give new in- 

 sight into almost every operation of nature (nearly every one 

 of which is accompanied by the radiation or reception of heat), 

 and would enable us to answer inquiries now put to physicists 

 in vain by every department of science, from that of the nat- 

 uralist as to the enigma of the brief radiation of the glow- 

 worm, to that of the geologist who asks as to the number of 

 million years required for the cooling of a world. 



When, however, we begin - to go beyond the points which 

 seem, like this, to invite our very next steps in advance, we 

 cannot venture to prophesy, and must content ourselves with 

 the knowledge that through our study we are beginning to 

 apprehend the full meaning of one of the early great ones of 

 science, who described man as the meeting point of two in- 

 finities. That there is an infinity of space above him, man 

 has long known, but that there is another absolute infinity, and 

 what the possibilities are which lie in the infinitesimals of space, 

 he is but beginning to realize. The secular movements, whose 

 accomplishment demands more than a million years of time, 

 he has already considered ; but of the consequences which may 

 result from a more careful study of actions occurring in the 



