HAMILTON SCIENTIFIC ASSOCIATION. 77 



ultra-red and the ultra-violet rays, the latter being demonstrated 

 by means of silver chloride, which darkened under their action. 



We now come to one who came very nearly being the first dis- 

 coverer of photography — Thomas Wedgwood. Born May 14th, 

 1771, being the fourth son of Joseph Wedgwood, the famous 

 potter. Investigations by one Schulze and his successors had dem- 

 onstrated the properties of nitrate of silver and the chloride of sil- 

 ver. The optical works by Priestly and Hershall had suggested 

 the employment of the lense. It yet remained for someone to com- 

 bine these factors. This is what Wedgwood claimed to have done. 



His method was to soak paper or white leather in a solution of 

 silver nitrate and to expose this sensitized material under a fern or 

 engraving to the action of light analogous to our printing methods 

 of to-day. And in this the first requisite of photography was sup- 

 plied. But the difficulty of preventing the object thus obtained 

 from fading remained for some years, for Wedgwood we find 

 states in reciting the details of his method to " Davy " that noth- 

 ing but a method that would prevent the unshaded parts from col- 

 oring when exposed to light would complete and make his process 

 successful. 



Wedgwood was, we find, also the first to experiment with 

 the camera-obscura. But found that the image thus obtained was 

 too faint to affect in a moderate time the sensitized material em- 

 ployed. Whether or not these pessimistic conclusions deterred 

 Wedgewood is not made clear, for we cannot find any further 

 record of his achievements. 



We now come to Niepce and the first photographic record of 

 permanency. This man first attracted attention by his attempt to 

 substitute the usual lithographic stone for the production of a local 

 quarry. Finding this stone unsuitable, he next tried polished 

 metal plates, his object being to supplant the method of engraving 

 upon the stone by first oiling or varnishing or otherwise making 

 the line engraving transparent, placing it upon the metal plate 

 previously coated with various substances and then exposing the 

 whole to light. Of what these first substances were we have no 



