72 



Binocular Stands. 



In the course of 1897 we introduced a new form of binocular microscope 

 after designs by Mr. HORATIO S. GREENOUGH in which stereoscopic vision is 

 obtained, not by division of a pencil of light passing through a single object- 

 glass, but by a combination of two microscopes, complete in themselves and 

 combined with erecting prisms. 



This type of binocular microscope is also adjustable by means of rack 

 and pinion. 



The application of erecting eye -pieces fitted with PORRO- prisms 

 affords a convenient means of adjustment for varying intra-pupillary distances. 

 The pairs of objectives are mounted upon slides and require adjusting for 

 each stand separately, consequently it is necessary to send us the tube when sub- 

 sequently ordering pairs of lenses. The mount of one of the objectives is pro- 

 vided with screw threads to facilitate equally sharp focusing of both lenses 

 in cases where inequalities of power of vision in the two eyes require 

 compensating. 



We supply pairs of objectives for these microscopes in five classes (see pp. 18 

 and 21), viz: (55), (ao), (a?), (M and (Ph. 



Pairs of objectives are immediately interchangeable on any particular stand 

 for which they have been adjusted. The mounts of lenses of the dry series are 

 fitted to their slides in such a manner as to obviate the necessity of readjust- 

 ment after substituting one set for another. 



The most suitable eye-pieces are the HUYGENIAN eye-pieces 1 3; also a 

 RAMSDEN eye-piece, which is specially constructed for these instruments and is 

 known under the name of Orthomorphie eye-piece 4, because of the original 

 design of combining it with small diaphragms in the region of the upper micro- 

 scopic nodal point in order to satisfy Mr. GREENOUGH's orthomorphic require- 

 ments. (For further information see "Zeitschr. f. wissensch. Mikrosk.", vol. XIV, 

 1897, pp. 294298.) 



Price of Orthomorphic eye-piece 4: Marks 7. . Code-word: Palmito. 



The magnifications obtainable by combinations of the above objectives and 

 eye-pieces range between 8 and 72 diameters. (See tables on p. 21, which 

 also contain data of free working distances and of diameters of the visible areas 

 of objects.) 



