87 



For the purpose indicated above the large ABBE drawing cameras, 

 Nos. Ill and 112, are fitted with a cap encasing the prisms from above, which is 

 provided with moderating glasses of varying degrees of density, and with a 

 similarly equipped excentric disk pivoted below the prisms. In both appliances 

 only five of the six openings contain smoked glass, the sixth remaining 

 clear so that the cap and disk may remain attached although the brightness of 

 the image or of the drawing surface may not require moderating. 



In order to enable the increased cone of emerging rays obtained with low 

 magnifications being fully utilized, the usual ABBE cube with aperture of 1 mm 

 can, with the large drawing apparatus, quickly and conveniently be exchanged 

 for another of 2 mm aperture (see Fig. 48 b ). 



Glasses to correct defects of vision are, if required, supplied with our drawing 

 apparatus. 



*0ld form of Camera lucida, No. 109. This drawing prism is only 

 supplied in the form shown in Fig. 46. The prism casing turns round a hori- 

 zontal axis and is also adjustable in elevation. It fastens to the tube by means 

 of a sprung collar and can easily be turned aside. 



No. 109 : Drawing prism (Camera lucida), incl. case 



Price : Code-word : 

 Marks 21. . Patron. 



In conjunction with Dissecting Stand P II, which, when used as a drawing 

 apparatus with low magnifications, may be extremely useful in many ways, we 

 supply this simple drawing prism exclusively (see pp. jq 81). 



^09 



Fig. 46. Drawing 1 prism (Camera lucida), No. 109. ( 8 / 4 Full Size.) 



The ABBE drawing cameras are constructed in three different forms: 



1. * Small ABBE Drawing Camera, No. 110. The prism casing and 

 the mirror the latter supported by an extended arm about 105 mm (4 in.) long - 



