326 THK APPLICATIONS OF PHYSICAL FORCES. [BOOK in. 



necessary appliances, lie can obtain, with a comparatively' trifling 

 expenditure of time and labour, a considerable mass of documents, 

 which will have, beyond everything, this exceptional value, that the 

 fidelity of the agent who has portrayed and fixed them, namely, 

 light itself, cannot be questioned. 



Photography can pass from the infinitely small to the infinitely 

 great. The celestial phenomena have come under its action The 

 spots in the sun, the mountains in the moon, eclipses, and the 

 physical peculiarities which they have offered. The planets and starry 

 constellations have been attempted. All has not yet been said 



of the services which this won- 

 derful art may one day render to 

 astronomy ; but what has already 

 been done in this direction has 

 been exaggerated, and, at any 

 rate, the true role of astronomical 

 photography, and the influence it 

 may have on the progress of 

 science, have not always been 

 properly understood. We think, 

 therefore, that it will not be out 

 of place to define them more 

 F '- - Minute disc : AracJmordiscus. clearly. "We cannot do better 



Facsimile of a microscopic photograph. > 



than quote verbatim what was 



said on this subject at a Conference, in 1868. by an astronomer 

 whose science and experience are only equalled by his modesty, 

 the author of the Sdenograpliie. the venerable Masdler. 



" Most of those who hear me/' said he, " can remember that imme- 

 diately after the discovery of photography such hopes were expressed 

 as were only equalled by those of Descartes and his contemporaries 

 after the discovery of astronomical glasses. They pitied the unfortunate 

 men of science who had passed their whole life without interruption 

 in observing, measuring, drawing. Not only were they going to 

 do the same thing without trouble and in much less time, but they 

 would obtain better results, more exact, and more in detail than 

 heretofore. What has cost me seven years, the determination 

 of the surface of the moon, was to be much better done in seven 

 seconds. 



