CH. VIII. 



PHO TO-MICROGRA PH Y. 



197 



than for ordinary photography. The ordinary negative is liable to 

 have too much contrast, but this is rarely the case with photo-micro- 

 graphs. Any good developer may be used. One can as a rule do no 

 better than to follow the directions accompanying the plates used. 

 The writer's experience has been so satisfactory with Mr. Walmsley's 

 developers that he desires to call attention to them. The developers 

 are easily made, will develop anything that can be developed and one 

 can feel confident that if the negative is not good the fault does not lie 

 with the developer. 



The best photo-micrographic negatives made by the writer were made 

 with Cramer's instantaneous isochromatic plates, and the image com- 

 menced to appear with Walmsley's developer in 2 1 ; to 3 minutes and 

 the development was completed in 12 to 15 minutes. Excellent nega- 

 tives have been developed in less time and also when it required half 

 an hour to develop them. The temperature has much to do with the 

 development of correct!}' exposed negatives, so that no rule can be 

 given. Metol and rodinal developers have also given excellent results 

 and in a shorter time. 



If one desires the best possible results it is necessary to avoid the 

 light in developing. Even the ruby light of the dark room should be 

 avoided as much as possible, for the plates used are made purposely 

 sensitive to the longer rays of the spectrum (§ 193). After the nega- 

 tive is developed and washed it should not be taken to the light till it 

 is fixed. Too much light after development and before fixing, injures 

 the clearness of the negative. 



Fig. 153. Focusing Glass. " It is achromatic, con- 

 sisting of a double convex crown lens and a negative 

 meniscus flint lens cemented together." It screws 

 into the brass tube and is thus adjustable, enabling 

 one to focus the pencil mark in the clear area of the 

 focusing screen (Fig. 150) with great accuracy. It also 

 serves to focus the image with ease and accuracy. 

 The eye must not be too close to the upper end of the 

 focusing glass or the field will be restricted. (From 

 the Gundlach Optical Co. ) 



§338. Labeling and Care of Negatives. — The care, printing, etc. , 

 of negatives is like that of ordinary negatives. It is well to label them 



