106 



E. Miscellaneous Accessory Apparatus. 



Eye-pieces for special purposes, 



* ABBE'S Stereoscopic Eye-piece, No. 189, Fig. 60. This apparatus is 



designed for stereoscopic as well as ordinary binocular observation of microscopical 

 objects with any desired magnification. (See "CARL's Repertorium", vol. XVII, 

 1881, pp. 197 224; also "Journ. of the R. Micr. Soc." (2), vol.1, 1881, pp.203 211.) 



Fig. 60. ABBE'S Stereoscopic Eye-piece, No. 189. ( 2 / 3 Full Size.) 



The division of the pencil of rays emerging from the objective, with the 

 object of producing two separate images, is effected at the upper end of the 

 tube by partial reflection at a thin stratum of air between the two prisms a 

 and b. The bisection of the pencils for producing stereoscopic effect is made by 

 adjustable semi-circular stops placed over the eye-pieces; without these, i. e., with 

 fully exposed eye-pieces, the instrument gives binocular vision without specific 

 stereoscopic effect, 



