* Paired Objectives for the Binocular Microscopes. 



The combinations PI (Water Immersion), 83, 82, 3o and one of still lower 

 power, namely of 55 mm (about 2V 4 in.) focal length, for use with binocular 

 microscopes, are supplied in a special form of setting and mounted in pairs on 

 metal slides. 



We designate such paired objectives: (55), (a<>), (W), (as), (Plj- 



A pair of suitable diaphragms to slip on, which should be used whenever 

 it is desired to obtain an image perfectly uniformly sharp up to the margin, is 



supplied with each set of paired objectives. 



Regarding the use of the paired objectives (Pi) see p. 21. 



For tables of magnification, free workiny distance and area of visible field 

 of the paired objectives Nos 14: in combination with the Binocular Microscope, 

 see p. 2(1. 



HUYGENIAN Oculars. 



We supply HUYGENIAN oculars for use with achromatic objectives in 

 five different powers. The various focal lengths of these oculars are serially 

 graduated so that, with due regard to their peculiar variations in the position of 

 their lower focal points, the magnifications X 3, 4, 5.5, 7 and 9 are obtained if 

 the tube-length of 160 mm be maintained throughout. 



We make also a HUYGENIAX Ocular 2* with iris-diaphragm similar to the 

 compensating ocular 4*. What has been said with regard to compensating ocular 

 4* applies equally to this HUYGENIAN ocular 2*. (See p. 18.) 



Regarding oculars for special purposes see under heading of Accessory 

 Apparatus, pp. 86 89. 



We would particularly emphasise the fact that HUYGENIAN oculars are designed for use with 

 achromatic objectives only. 



Concerning the employment of achromatic objectives with compensating 

 oculars, it is to be pointed out that such oculars are only suitable therewith in the case 

 of objectives of larger num. Ap., O.85 and upwards, i. e., system DD and higher powers. 



Seios, cfcna. 



