14 SMITHSONIAN MISCELLANEOUS COLLECTIONS. 



very important province of measuring" the heating power of the 

 sun through the enormous range of wave-lengths inchided in 

 Doctor Langley's observations, his work was unique, and that it 

 would be profoundly regretted by the scientific men of all countries 

 if anything were to occur to check its vigorous prosecution or to 

 diminish the resources of the Astrophysical Observatory of Wash- 

 ington for work of any kind in its province. The result was that 

 Congress continued the appropriation for the maintenance of the 

 observatory, and its wisdom in doing so no thoughtful man who 

 has reflected upon the history of science can doubt. For if there 

 is anything which history teaches, it is that every important scien- 

 tific truth may be translated into useful activity for mankind. 



There can be no doubt in the mind of any competent thinker in 

 this field that from Doctor Langley's researches with the bolometer, 

 the photographic plate, and various instruments of accurate mechan- 

 ism devised or perfected by him will date discoveries of vast im- 

 port, not merely to scientific investigators, but to the world at large. 

 His first discoveries are sure to be written in the history of the nine- 

 teenth century as among the real glories of our country. They 

 combine profound original research, exquisite ingenuity, and a large, 

 philosophic view of the relations of his work to that which had gone 

 before and that which was sure to follow. 



But, while carrying on these original researches in his principal 

 field, his fertility of thought was seen in other directions calculated 

 to benefit his fellow-men. He did not fear to endanger his reputa- 

 tion as an original investigator by spreading scientific knowledge 

 in various forms among the people at large, and in terms not merely 

 intelligible, but attractive. Courses of lectures and articles in maga- 

 zines addressed to men and women of various attainments testify 

 amply to this. Some of these rose into the higher regions, not only 

 of science, but of literature. Notable especially was his address in 

 1888, on retiring from the presidency of the American Association 

 for the Advancement of Science. It was entitled "The History of a 

 Doctrine" — this doctrine having relation to radiant energy. Both 

 in thought and style it is a masterpiece and it reveals the mind of a 

 philosopher. Many passages give contributions to philosophic 

 thought, but I select one, which runs as follows : "We have, per- 

 haps, seen that the history of progress in this department of science 

 is little else than a chapter in that larger history of human error 

 which is still to be written ;" but he adds : "Shall we say that the 

 knowledge of truth is not advancing? * * * j^- ^^ advancing, 

 and never so fast as today ; but the steps of its advance are set on 



