378 THE PHOTOGRAPHIC IMAGE. 



Heinrich Schulze, the son of a Gerinan tailor, who was born in the Duchy 

 of Madgeburg, in Prussia, in 1687, and who died in 1744, after a life of 

 extraordinary activity as a linguist, theologian, physician, and philoso- 

 pher. In the year 1727, when experimenting on the subject of phos- 

 phorescence, Schulze observed that by pouring nitric acid, in which 

 some silver had previously been dissolved, on to chalk, the undissolved 

 earthy residue had acquired the property of darkening on exposure to 

 light. This effect was shown to be due to light, and not to heat. By 

 pasting words cut out in paper on the side of the bottle containing his 

 precipitate, Schulze obtained copies of the letters on the silvered chalk. 

 The German philosopher certainly produced what might be called a 

 temporary photogram. Whatever value is attached to this observa- 

 tion in the development of modern photography, it must be conceded 

 that a considerable advance was made by spreading the sensitive com- 

 pound over a surface instead of using it in mass. It is hardly necessary 

 to remind you here that such an advance was made by Wedgwood and 

 Davy in 1802.* The impressions produced by these last experimenters 

 were unfortunately of no more permanence than those obtained by 

 Schulze three quarters of a century before them. 



It will perhaps be safer for the historian of this art to restrict the 

 term photogra])h to such impressions as are possessed of permanence. 

 I do not of course mean absolute permanence, but ordinary durability 

 in the common-sense acceptation of the term. From this point of view 

 the first real photographs, i. e., permanent impressions of the camera 

 picture, were obtained on bitumen films by Joseph Nicephore Niepce, 

 of Chalons-sur-Saone, who, after about 20 years' work at the sub- 

 ject, had perfected his discovery by 1826, Then came the days of silver 

 salts again, when Daguerre, who commenced work in 1824, entered into 

 a partnership with Niepce in 1829, which was brought to a termination 

 by the death of the latter in 1833. The partnership was renewed be- 

 tween Daguerre and Niepce de St. Victor, nephew of the elder Niepce. 

 The method of fixing the camera picture on a film of silver iodide on a 

 silvered copper plate — the process justly associated with the name of 

 Daguerre — was ripe for disclosure by 3838, and was actually made 

 known in 1839. 



The impartial historian of photography who examines critically into 

 the evidence will find that quite independently of the French pioneers 

 experiments on the use of silver salts had been going on in this coun- 

 try, and photographs, in the true sense, had been produced almost 

 simultaneously with the announcement of the Daguerreotype process by 

 two Englishmen whose names are as household words in the ranks of 

 science. I refer to William Henry Fox Talbot and Sir John Herschei. 

 Fox Talbot commenced experimenting with silver salts on paper in 



* "Au Account of a Method of Copying Paintings upon Glass, and of making Pro- 

 files by the Agency of Light upon Nitrate of Silver. Invented by T. Wedgwood, 

 Esq. With Observations by H. Davy." Journ. Eoyal Institutioii, 1802, p. 170. 



