METHODS EMPLOYED. 5 



remove the alcohol and washings. For producing transparency, oil of 

 cloves has been used, and the mounting has been done under thin, clear 

 covers, in a solution of Canada balsam in chloroform. 



All the negatives have been made on glass thoroughly cleaned and 

 lightly coated with a solution of wax and benzole, so that the collodion 

 film, previously made adherent to thin sheets of gelatine, could be safe- 

 ly removed from the plate. The flexible negatives, thus obtained, are 

 well adapted to the artotype process, and, as they can be indefinitely 

 preserved between the leaves of an ordinary scrap-book, are very desir- 

 able for a series of illustrations. In making the original negatives on 

 glass, the "wet collodion process," with the sulphate of iron developer, 

 has been exclusively employed. 



The prints correspond exactly with the negatives both in outline 

 and detail. No distortion occurs as in silver printing, in which process 

 the paper is subjected to prolonged washing. 



In many of the photographs the gray substance appears lighter in 

 shade than the white substance. This appearance is due to a greater 

 degree of transparency of the gray substance, in these sections, resulting 

 from the action of the oil of cloves, followed by an increased action of 

 the transmitted light on the sensitive collodion film of the negative, and 

 hence by a thinner deposit of ink over corresponding parts of the positive 

 plates from which the artotypes are printed. 



