SCIENCE IN THE INDUSTRIAL WORLD 



icals of various kinds. On examining them the following 

 morning he found to his astonishment that they were 

 completely developed, although nothing had been done 

 to them since their exposure. There was only one 

 explanation possible : the fumes of some of the chemicals 

 in the cupboard must have been responsible. And by a 

 careful process of elimination Daguerre finally deter- 

 mined that the fumes of mercury had produced the 

 effect. Carrying these experiments a little further he 

 found that by exposing his sensitized plate in the ordi- 

 nary manner and then holding it face downward over a 

 basin of warmed mercury, the image appeared quickly, 

 and could be made permanent by dipping the plate in a 

 solution of hyposulphite of soda. This may be con- 

 sidered the starting-point of modern photography. 



As there was no secret about the process used in 

 making these photographs, scientists all over the world 

 were soon duplicating Daguerre's experiments. Before 

 the eventful year closed, two Americans, Morse and 

 Draper, had succeeded in making a portrait of a person 

 the first ever taken. In making this first portrait the 

 operators powdered the face of the sitter and posed him 

 in bright sunlight, with eyes closed, for a period of half 

 an hour. Several attempts were made before anything 

 like a satisfactory result was obtained, the great diffi- 

 culty encountered being the strain of the glaring sunlight 

 upon the sitter's face, which was almost unbearable. 

 Finally a glass jar containing a blue-colored solution 

 was placed between the face and the sun, and the strain 

 relieved in this manner, so that a fairly good, if some- 

 what ghastly, portrait was made. 



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