154 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



XIII. 



THE NEW APOCHROMATIC MICRO -OBJEC- 

 TIVES AND COMPENSATING OCULARS OF 

 DR. CARL ZEISS. 



BY ADOLF SCHULZE, F.R.S.E., F.R.M.S. 



[Read 2Sth September, 1886.] 



Dr. Carl Zeiss has had the kindness to send me 

 for inspection four of his new aprochromatic objec- 

 tives, and three of his new compensating eyepieces ; 

 and as a short notice of only one of these objectives 

 has to my knowledge appeared in this country — 

 viz., in the Journal of the Royal Microscopical Society, 

 vol. vi., part 2, fol. 375-6, I trust that the following 

 remarks, culled chiefly from Dr. Abbe's pamphlet Ueber 

 Verbesserungen des Mikroskopes mit Hilfe neuer Arten 

 optischen Glases (" On improvements of the microscope 

 by the aid of new kinds of optical glasses"), may 

 be acceptable to the members of our society. 



Professor Dr. Ernest Abbe — who is " the first 

 living authority on microscopical optics/' and to 

 whom we are indebted not only for the greatest 

 recent improvements in the construction of micro- 

 objectives, but also for the theory of the formation 

 of microscoj)ical images by diffraction spectra, and 

 for lucid mathematical expressions of the relations 

 of aperture, resolving power, focal depth, &c. — 

 finding that the aperture of micro-objectives had 

 been pushed to almost its theoretical limit, and 

 foreseeing no adequate advantages in trying to 

 increase the aperture with the means hitherto at 

 our command, directed his attention to further 

 improvements by an entirely different method. 



In conjunct ion with Dr. Carl Zeiss, the eminent 

 optician of Jena, and with the assistance of Dr. 



