208 PHOTOMICROGRAPHY. [CH VIH. 



may be made. If, however, light and shade and fine details are to be 

 brought out with great distinctness, either an aristotype, platinotype or 

 a bromide print is preferable. In whatever way the print is made, it 

 is blacked on the back with soft lead-pencil, put over the drawing- 

 paper, and the outlines traced. 



OUTLINES OBTAINED DIRECTLY BY MEANS OF THE CAMERA. 



§ 350. While it is desirable to make photographs of objects in many 

 cases, this may frequently be avoided and a tracing made directly from 

 the camera. The object is arranged as for a photograph and well 

 lighted. Then the ground glass is changed for a plain glass and the 

 tracing paper is put over the glass. If the head and screen are covered 

 in some way the image may be seen and traced very easily. This will 

 give a reversed image, but that is easily remedied by turning the paper 

 over in making the tracing on the drawing paper. 



Frequently also one wishes to enlarge or reduce a drawing or outline 

 already made. If the figure or outline is placed in a good light the 

 image may be made of any desired size and either photographed or 

 traced as just described. Tracings of any desired size may also be ob- 

 tained of negatives, but for this one must employ the method of light- 

 ing described in § 335, where the clear sky is taken for a background 

 and illuminant. Of course artificial light may also be used, but it is 

 less satisfactory unless one has abundant facilities. 



An excellent method of making large diagrams is to use a photo- 

 graphic objective and project the image into a dark room, something 

 after the manner of a stereopticon, then one can trace the image directly 

 on the material on which the diagram is to be drawn. 



£351. Prints of Photo-Micrographs and Mechanical Printing. 

 After one's negatives are made, prints from them may be obtained 

 from a photographer, but from the author's experience, unless the pho- 

 tographer is familiar with the kind of printing necessary to bring out 

 the features most desired, the results will not be very satisfactory. It 

 is better to make one's own prints, and this can be very easily done 

 with the excellent aristotype and platinotype paper on the market. It 

 may also be well done with the bromide paper. The last has the advant- 

 age of being capable of furnishing prints by lamp as well as daylight. 



For mechanical prints, half tones and photogravures, one should get 

 first as good a negative as possible. And for photogravures the so- 

 called stripping plate should be used so that the picture will not be re- 

 versed. For half tones the print should have a good deal of contrast 



