Objectives and Eye-pieces. 



The Glass Works of Messrs. SCHOTT & Co. (which make a speciality of 

 materials for optical and other scientific purposes and which had been established 

 in Jena, with our co-operation, as the outcome of exhaustive experiments extended 

 over several years and carried out by Dr. SCHOTT and Professor 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 microscope lenses than the crown and flint glasses superseded by them.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 the chromatic and the spherical 

 aberrations and, consequently, effecting a much greater concentration of 

 light in the image than had previously been attainable. We introduced simul- 

 taneously eye-pieces specially adapted for use with these objectives which, beside 

 facilitating certain other advantages of minor importance, produce almost per- 

 fect achromatism and yield a sharp image over the whole area of the 

 visual field. 



By a special catalogue published in August 1886 these new combinations 

 were first made known under the designations of "Apochromatic Objectives", 

 "Compensating Eye-pieces" and "Projection Eye -pieces" respectively; 

 and they have since been most extensively adapted, have met with general 

 approbation, and have given most ample proof of the exceptional value of their 

 services in the field of scientific research. 



Side by side with the new objectives and eye-pieces we continue to supply 

 our older achromatic objectives with their accompanying ordinary eye-pieces. 

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



