30 



7. *Swing-OUt Condenser, Nos. 27 and 28, with iris-cylinder diaphragm 

 (Fig. 12). 



This form of condenser was introduced by us in 1894 (see Zeitschr. f. wiss. 

 Mikrosk., vol. XI, 1894, pp. 433440). The apparatus offers the advantage of 

 having the condenser and the iris-cylinder diaphragm combined. By the aid of 

 a suitable mechanism the condenser system may be folded clear of the carrier 

 of the iris-cylinder diaphragm and swung aside so as to facilitate, by simple 

 means, a change from illumination by mirror and condenser (convergent rays) 

 to that by mirror alone (parallel rays). 



We supply the apparatus fitted ivith either the double or the triple lens-combination. 

 Price of swing-out condenser, No. 27 (with No. 25J Marks 43. . Code-word: Papeleta. 



>, ,, ,, 28 ( ,, ,, 26J ,, 50.. Papeneo. 



In subsequent orders for condensers specified under 5 7 the 

 factory number of the stand should he mentioned. 



8. * Centring Achromatic Condenser, No. 29 (Fig. ll d ), numerical aper- 

 ture 1.0, equivalent focal length 14 mm. 



In this form of condenser the concentration of the illuminating rays is 

 effected by means of an iris-diaphragm situated between the lenses, 

 wherefore the diaphragm-carrier of the illuminating apparatus should 

 be moved aside during use. 



Price in case: Marks 75. . Code-word: Fapion. 



Although in comparison to the condensers specified under 57, which consist of 

 ordinary lenses, achromatic condensers may afford scarcely any special advantage in 

 visual observation, they admit, owing to the more complete union of rays effected by 

 them, of a sharp image of the source of light being projected into the plane 

 of the object, and this is frequently advantageous for the purposes of photo-micrography 

 and projection. 



9. *Centring Achromatic Condenser possessing great focal distance, 



No. f30, numerical aperture and focal length as above. This form of condenser 

 was suggested by Professor ROLLETT of Graz. It is specially designed to admit 

 of the use of ZOTH'S cooling trough (see p. 114) which should be placed directly 

 below the object. 



The aperture is regulated by means of the iris-diaphragm of the illuminating 

 apparatus. 



Price in case: Marks wo. . Code- word: Papula. 



10. *Centring Achromatic Condenser with enlarged aperture, No. 31, 



numerical aperture 1.30, equivalent focal length 9 mm, Fig. 11 e . By virtue of 

 its large numerical aperture this condenser admits of the application of an 

 exceptionally large or of a very oblique illuminating cone, unaffected 

 with the pronounced aberrations invariably present in the cone of rays yielded 

 by ordinary non-achromatic condensers. The slides used with this apparatus may 

 not exceed a thickness of about 0.7 mm. 



