152 



OR AM' ING \\'ITH THE MICROSCOPE 



\_Cff. V 



If the micrometer scale is added to every drawing, there is no 

 need of troubling one's self about the exact distance at which the 

 drawing is made, convenience may settle that, as the special mag- 

 nification in each case may be determined from the scale accompany- 

 ing the picture. It should be remembered, however, that the con- 

 ditions when the scale is drawn must be exactly as when the draw- 

 ing was made. 



FIG. 132 A. B. Abbe Camera Lucida. (A.} In this figure the camera 

 lucida is in position for draining. The ring or collar supporting the mirror 

 is graduated so that the angle of the mirror- may be exactly determined. 

 Smoked glasses serve to modify the light from the microscope or from the 

 drawing surface as needed. By means of a clamping ring the instrument may 

 b raised or lowered to accommodate the eye-point in dijferent oculars. 



(B.) In this figure the camera lucida prism is turned back so that one 

 may look directly into the ocular. (Cuts loaned by the Bausch & Lomb Opti- 

 cal Co.) 



208. Drawing at Slight Magnification. Some objects are 

 of considerable size and for drawings should be enlarged hut a few 

 diameters, 5 to 20. By using sufficiently low objectives and differ- 

 ent oculars a great range may be obtained. Frequently, however, 



