CHAP.V. NEW APPLICATIONS OF LIGHT. 33 



so delicate and beautiful that probably nothing in mod- 

 ern photography can surpass them. For several years 

 they were the only portraits taken by the agency of 

 light, but they were very costly, and were therefore com- 

 pletely superseded when cheaper methods were dis- 

 covered. 



About the same time a method was found for photo- 

 graphing leaves, lace, and other semi-transparent objects 

 on paper, and rendering them permanent, but this was of 

 comparatively little value. In the year 1850, the far 

 superior collodion-film on glass was perfected, and nega- 

 tives were taken in a camera-obscura, which, when 

 placed on black velvet, or when coated with a black com- 

 position, produced pictures almost as perfect and beauti- 

 ful as the daguerrotype itself, and at much less cost. 

 Soon afterward positives were printed from the trans- 

 parent negatives on suitably prepared paper, and thus 

 was initiated the process, which, with endless modifica- 

 tions and improvements, is still in use. The main ad- 

 vance has been in the increased sensitiveness of the 

 photographic plates, so that, first, moving crowds, then 

 breaking waves, running horses, and other quickly mov- 

 ing objects were taken, while now a bullet fired from a 

 rifle can be photographed in the air. 



"With such marvellous powers, photography has come 

 to the aid of the arts and sciences in ways which would, 

 have been perfectly inconceivable to our most learned 

 men of a century ago. It furnishes the Meteorologist, 

 the Physicist, and the Biologist, with self -registering in- 

 struments of extreme delicacy, and enables them to pre- 

 serve accurate records of the most fleeting natural phe- 

 nomena. By means of successive photographs at short 



