PRACTICAL PHOTOMICROGRAPHY. 117 



the sheet to drip as much as it will. Pure bibulous paper must 

 be used for this purpose. If the sheet after drying is placed 

 between sheets of blotting or pure filter paper previously im- 

 pregnated with sodic carbonate and dried, it will remain white 

 and good for weeks. Sensitizing and drying must be per- 

 formed in yellow or artificial light. All these matters are most 

 carefully treated in " Practical Guide to Photographic and 

 Photo-mechanical Printing Process " by W. K. Burton, C. E. 

 (London, Marion and Co?) and also in the book already alluded 

 to in the Scovill Photographic Series. 



The negative is laid face upwards in a " printing frame " 

 (fig. 30.) and on it is laid the albumenized paper face down- 



FIG. 30. PRINTING FRAME. 



wards, so that the albumen surface is in contact with the 

 gelatine film. The frame is then taken to the daylight and 

 printing commences. As a rule photo-micrographic negatives, 

 if thoroughly good, take longer to print than ordinary photo- 

 graphic negatives. In any case the printing must be carried 

 considerably beyond the stage when the print seems to look at 

 its best, as seen by opening one-half of the hinged back of the 

 printing frame. The operations of toning and fixing greatly 

 lessen the depth attained by the merely exposed print. 



When a batch of prints are printed, having after printing 

 been stored away in some suitable light-tight receptacle, we 

 proceed to the operations of toning, fixing, and washing. 



The prints are first immersed in water, being well covered 

 therein and kept moving and separate from each other. After 



