PRACTICAL PHOTO-MICROGRAPHY. 127 



grayness, while the half-tones should be from pale to dark gray 

 according to their nature. In our work there ought always to 

 be some part of the picture perfectly white when development 

 is complete, but often it is impossible to attain this ; our best 

 guide then, remains in the vigorous tone of the dark parts. 

 With the developer we have given on page 92 the image 

 ought not to begin to appear for at least 20 seconds, and devel- 

 opment with fresh solution may be expected to finish in about 

 two to three minutes. Yery rapid development points to over- 

 exposure, which is probably the most serious error that in our 

 special work can be committed. 



As soon as development is complete, the print is to be 

 flooded with acidulated water, not plain water. A dram of 

 acetic acid (glacial) to one pint of water will do, or a dram of 

 citric acid. If the water smells of acetic acid it will suffice. 

 Three applications of acid water for a minute or so each will 

 suffice to wash out most of the iron, the print being moved in 

 the acid water all the time ; washing in plain water till the 

 acid is eliminated follows, and then the print is fixed in the 

 ordinary bath of hypo, 1 part, water 5 parts made alkaline. 

 In this the prints should stay at least twenty minutes, then 

 they are washed in the manner detailed for albumen prints. 

 (Page 119.) 



The Eastman Company of Rochester, IT. S., prepare not 

 only bromide papers of the very highest quality, but also a 

 modification called Transferotype Paper. For the photo- 

 micrographer "Transferotype" is a most valuable process. 

 The printing and other processes, up to and including the final 

 washing, are exactly the same as for ordinary bromide paper, 

 but as in transf erotype the sensitive emulsion (insoluble) is laid 

 over a soluble stratum of gelatine on the paper, it is evident 

 that by dissolving the soluble gelatine we can remove the 

 paper. If we can stick our image-bearing film to a transparent, 

 or semi-transparent, or translucent support, as glass or opal, 

 and then remove the paper, it is evident that we can produce 

 a transparent or translucent positive reversed as regards right 

 and left certainly, but for us this reversal is of no import. 



By the following means, then, we can produce by " Trans- 



