ELEMENTARY PHOTO-MICROGRAPHY. 23 



The whole of the processes hereinafter described 

 are intended to be carried out by artificial light. 



There is a difference betwixt the visual and the 

 actinic foci ; objectives corrected for photography 

 are sold, but ordinary objectives made by good 

 firms give results not to be despised. Even with 

 high powers tolerable negatives can be obtained, 

 and the brain work of a practical manipulator will 

 often compensate for lack of expensive apparatus. 

 USE OF EYEPIECES. 



The use of eyepieces is condemned by some 

 writers without much reason. If the eyepiece be 

 not used, a long extension of camera is needed, 

 whereby the apparatus becomes troublesome, and 

 the result is not one jot better than when the eye- 

 piece is employed. The loss of light occasioned by 

 its use is more than compensated for by the com- 

 pactness of the arrangement, whereby the operator 

 may see or control the whole of his focussing and 

 lighting from one position. A trifle longer ex- 

 posure is of no moment to a beginner, since the 

 time lost in this way is saved in the facilities 

 offered for focussing. The errors of objectives also 

 are corrected by eyepieces, and good results can 

 be obtained when using them for photographic as 

 for visual purposes. The C eyepiece, although 

 giving great power of enlargement, is not recom- 

 mended when a low power will do. Yet the writer 



