THE HISTORY OF A DOCTRINE. 395 



fact tliat tlirougli its aid nature obeys us more and more ; proving 

 itself by such, material evidence as is found in the practical appli- 

 cations of the doctrine, in the triumphs of modern photography, 

 in the electric lights in our streets, and in a thousand ways which 

 I will not pause to enumerate. 



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

 for us in the history of what has been said. I will venture to ask 

 the attention to one more, perhaps a minor one, but of a practical 

 character. It is that in these days, when the advantage of organi- 

 zation is so fully realized, when there is a well-founded hope that 

 by co-operation among scientific men knowledge may be more 

 rapidly increased, and when in the great scientific departments of 

 government and elsewhere there is a tendency to the formation of 

 the divisions of a sort of scientific army — a tendency which may 

 be most beneficially guided — 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 say that there is a very great deal of this human 

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

 unchanging as this nature itself, and one which can not always 

 advantageously be remodeled into a piece of even the most re- 

 fined bureaucratic mechanism, but will work effectively only in 

 certain ways, and not always at the word of command, nor always 

 best in regiments, nor always best under the best of discipline. 



Finally, if I were asked what I thought were the next great 

 steps to be taken in the study of radiant heat, I should feel un- 

 willing to attempt to look more than a very little way in advance. 

 Immediately before us, however, there is one great problem wait- 

 ing solution. I mean the relation between temperature and radia- 

 tion ; for we know almost nothing of this, where knowledge would 

 give new insight 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 physi- 

 cists in vain by every department of science, from that of the 

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

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

 ion 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 can not 

 venture to prophesy ; for we can hardly discriminate among the 

 unlimited possibilities which seem to open before a branch of 

 knowledge which deals especially with that radiant energy which 

 sustains, with our own being, that of all animated nature, of 

 which humanity is but a part. If there be any students of Nature 

 here, who, feeling drawn to labor in this great field of hers, still 

 doubt whether there is yet room, surely it may be said to them. 



