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148 THE RISE AND PROGRESS OF PHOTOGRAPHY. 
great Josiah Wedgewood. Wedgewood and Davy became sien 
friends, and for some time continued their researches togethe 
e pr duced many beautiful copies of drawings, leaves, leeds 
of partial value, for a new difficulty now presented itself: the 
beautiful pictures obtained with so much trouble patience 
when exposed to daylioht gradually darkened all ov 
st now pass over a few years, during which time we 
occasionally hear of various experimenters using the different 
salts of silver as 1 dicks predecessors had done; among them may 
ak mentioned Seebeck, Guy Enis. Draper, Ritter, and Wollas- 
= 1814, we find the i ites Niépce likewise engaged in 
prosecuting aseries of studies in this new light process, and 
about twelve years later we hear of him engraving by the same 
process ; to do this he aR metallic Bg bier ah: them 
with asphaltum, and then exposed them to light in the camera 
insoluble, whereas the shaded parts were washed away with oil of 
lavender, which left bare the metallic surface of the scab and 
- which was then nieces In 1824 Louis Jacques Daguerre, the 
inventor of the diorama, experimented also sie the nitrate 
and chloride of a employin 
fact thata i spoon ad ih on a mn aes sre 
treated with iodine, ha alk eft it etal 
e pine tole fone on for a more active and 
cbs mie but wi t was his spr 
