Objectives and Oculars. 



The Glass Works] of SCHOTT & GENOSSEN, which make a speciality of 

 glasses for optical and other scientific purposes as the outcome of exhaustive ex- 

 periments, with our co-operation, extended over several years and carried out by 

 SCHOTT and ABBE, succeeded in 1884 in producing a series of |new glasses 

 possessing certain refractive |and (dispersive properties which [render them more 

 valuable for the construction of microscope lenses than the crown and flint glasses 

 superseded by them. 



The use of these | glasses, combined with the application of entirely new 

 formulae, has enabled us, since 1886, to produce microscope objectives 

 with markedly superior correction of both chromatic and sphejri- 

 cal aberration and, consequently, effecting a much [greater con cent r|a- 

 tion of light in the image than had previously been attainable. We introduced 

 simultaneously oculars specially adapted for use with these objectives which, beside 

 facilitating certain other advantages of minor importance, iproduce alm|ost per- 

 fect achromat-ism an|d yield a sharp image over the w|h|ole area 

 of the visual field. 



By a special catalogue published in August 1886 these new combinations 

 were first made known under the designations of "A|pochroma|ti;c Objectives", 

 "Compensating Oculars" and "Projection Oculars" respectively; and they 

 have since been most extensively adopted, have met with general approbation, 

 and have given most ample proofj of the exceptional value of their utility in the 

 field of scientific research. 



Side by side with the new objectives and oculars we ^continue to supply 

 our older achromatic objectives with their ' accompanying ordinary oculars. 

 For, although in the more difficult branches of microscopical research the apo- 



