Objectives and Eye-pieees. 
In our previous catalogue (No. 28, issued in 1889) we referred to the 
advance made, through our efforts, a few years previous to the publication of 
that catalogue, in the practical development of the microscope. It was there 
pointed out that this advance was, in a great measure, due to the results obtained 
in the production of new glasses (borate and phosphate glasses in particula]') 
by the ''(llastechnisches Laboratorium Schott and (jenossen", which has been 
established here, with our cooperation, as the outcome of long continued ex- 
periments by Dr. Schott and Prof. Abbe. By the use of these new glasses, 
which by their properties with respect to refractive power' and dispersion con- 
stitute a much superior material for the construction of microscope lenses, and 
the application of new formulae in the construction of the lenses, we have, since 
1 886, produced microscope objectives which possess a considerably m ore 
perfect correction both of chromatic and spherical aberration, 
and therefore a much greater concentration of light in the image, than had hitherto 
been attained. We also introduced eye-pieces specially adapted for use with these 
objectives, which, in addition to other advantages of minor importance, produce 
almost perfect achromatism and give a sharp image over the whole visual field. 
These new combinations which were first published in August 188() under 
the designations "Apochromatic Objectives'' and "Compensating Eye-pieces" and 
■"Projection Eye -pieces" are now extensively used and appreciated (we refer to 
the numerous comments in various scientific and technical periodicals and works), 
and have stood the test to which they were put as a means of advanced scientific 
research. At the request of eminent microscopists the series of these objectives 
has been increased by the addition of a few new types (vid. l^elowj. 
(Bazl 
