29 



With the swing-out condenser (which see under sub-head 7) the iris- 

 cylinder diaphragm is combined with the condenser system in the same sliding 

 sleeve. (See Fig. 12.) 



The cylinder-diaphragms and the iris-cylinder diaphragms, as supplied with 

 the ABBE illuminating apparatus, can also be used in connection with the sliding 

 sleeve of Stand IV b . 



In subsequent orders for cylinder and iris-cylinder diaphragms 

 the factory number of the stand with which they are to he used 

 should be qiioted. 



3. The Iris-Diaphragm, No. 23. The ordinary iris -diaphragm, as always 

 supplied with the illuminating apparatus, may also be obtained singly. 



Pticc: Marks w. . Code-word: Panzudo. 



4. Diaphragms for dark-ground illumination, No. 24. As a thoroughly 



good dark-ground illumination is only possible when the diameter of the 

 central stop of the diaphragm bears a certain definite relation to the numerical 

 aperture of the objective, we shall no longer supply these stops with the ABBE 

 illuminating apparatus but will send them, together with any necessary stops for 

 slipping or screwing into the lens mounts, to order and at special rates only. 

 When ordering, the objectives which are to be used should be specified, since 

 their apertures and the nature of their mounts govern the size of the stops. 

 It should also be stated whether they are intended for a condenser of 1.20 or 

 for one of 1.40 numerical aperture (see Directions for using the Illuminating 

 Apparatus). 



Price : Code-words : 



a) Central-stop diaphragm with button for the central stops Mk. 0.50. Papado. 



b) Central-stops, each /. -. . Papagallo. 



c) Objective-stops, to screw into the mounts, for achro- 

 matic objectives, each 0.60. Papaliua. 



d) Objective -stops, to slip into mounts from above, for 



apochromatic objectives, each 7.50. Papanatas. 



Objectives fitted with correction collars are not suitable for dark- ground 

 i llumination. 



5. Condenser Combination, double lens, No. 25 (Fig. ll a ), numerical 

 aperture 1.20, equivalent focal length 12 mm, in sliding sleeve. 



Price: Marks 20. . Code-word: Papaga. 



6. Condenser Combination, triple lens, No. 26 (Fig. ll b ), numerical aper- 

 ture 1.40, equivalent focal length 8 mm, in sliding sleeve. 



Price: Marks 25. . Code-word: Papelear. 



