4 THE A B C OF PHOTO - MICROGRAPHY 



a solution of silver nitrate, which soon faded 

 from not being fixed. There is no record of 

 any further advances in this direction until 

 1837, when the Rev. J. B. Reade obtained a 

 series of very satisfactory photo-micrographs 

 of insect and vegetable preparations on paper 

 sensitized with an infusion of galls, table salt 

 and silver nitrate. These prints proved to be 

 permanent and of such excellent quality that 

 a ready sale was found for them. The optical 

 work was done with the solar microscope. 

 After Daguerre's discovery of the photo- 

 graphic process to which his name was given, 

 most excellent pictures of microscopic objects 

 were made by it, the oxyhydrogen light being 

 used as the radiant for the first time of which 

 we have any record. A little later Dr. Donne, 

 of Paris, issued a work on microscopical anat- 

 omy, illustrated by photo-micrographs, taken 

 on daguerreotype plates and chemically etched 

 so that they could be printed from in ink. 

 Their excellence was marked, and they were 

 probably the first photo-micrographs ever 

 published as book illustrations. 



From that time more than a half century 

 ago there has been continual progress in 

 the art, until it has reached an excellence un- 

 dreamed of, and is universally in use the world 



