CH. I.] 



MICROSCOPE AND ACCESSORIES. 



i.S 



by 



Tube-length " i 

 Millimeters. 



Length in Millimeters and Parts included in " Tube-Length 

 Various Opticians.' 1 ' 

 Pts. included 

 in " Tube- 

 _a length." 

 .b See Diagram. 



...c fGrunow, New York 203 mm. 



E. Leitz, Wetzlar 170 mm. 



I Nachet et Fils, Paris . . • • 146 or 200 mm. 



a-d \ Powell and Zealand, London .... 254 mm. 



I C. Reichert, Vienna 160 to 180 mm. 



I Spencer Lens Co., Buffalo 235 or 160 mm. 



[W. Wales, New York 254 mm. 



Bausch & Lomb Opt. Co., Rochester. . 216 or 160 mm. 



Bezu, Hausser et Cie, Paris 220 mm. 



Klonne und Miiller, Berlin i6o-i8oor254tnm. 



W. & H. Seibert, Wetzlar 190 mm. 



Swift & Son, London 165 to 228^ mm. 



C. Zeiss, Jena 160 or 250 mm. 



Gundlach Optical Co., Rochester . . .254 mm. 



R. Winkel, Gottingen 220 mm. 



Ross & Co., London 254 mm. 



R. & J. Beck, London 254 mm. 



J. Green, Brooklyn 254 mm. 



Hartnack, Potsdam 160-180 mm. 



VeVick (Stiassnie) Paris 160-200 mm. 



Watson & Sons, London 160-250 mm. 



Thickness of Cover- Glass for Which Non-Adjustable Objectives are Corrected by 



Various Opticians. 



J. Green, Brooklyn. 



J. Grunow, Brooklyn. 



Powell and Lealaud, London. 



Spencer Lens Co., Buffalo. 



W. Wales, New York. 



Watson & Sons, London. 



Klonne und Miiller, Berlin. 



E. Leitz, Wetzlar. 



R. Winkel, Gottingen, Germany. 



Ross & Co., London. 



Bausch & Lomb Optical Co., Rochester. 



C. Zeiss, Jena. 



C. Reichert, Vienna. 



Gundlach Optical Co., Rochester. 



W. & H. Seibert, Wetzlar. 



R. &J. Beck, London. 



J. Zentmayer, Philadelphia. 



Nachet et Fils, Paris. 



Bezu, Hausser et Cie, Paris. 



Swift and Son, London. 



Fig. 24. 



yV^mm. 



Jfj^mm. 



T l A mm - 



1 5 20mm 



if^-emm. 



*The information contained in these tables was very kindly furnished by the 

 opticians named, or by consulting catalogs. In most of the later catalogs the in- 

 formation is definite, and many makers now not only put their names and the 

 equivalent focal length on their objectives, but they add the numerical aperture 

 (J 29) and the tube-length for which the objective is corrected. This is in accord- 

 ance with the recommendations of the author in the original paper on '■tube- 

 length," CProc. Amer. Soc. Micr., Vol. IX, p. 168. also by Bausch, Vol. XII, p. 



