8 



Abbe's substage condenser; one or more lenses ground 

 into the form of a truncated cone above, fit just below 

 the stage ; the diaphragms (of six different sizes) are 

 situated below the lenses and can be moved from the 

 centre by a rack and pinion and also rotated round the 

 optical axis. 



Apochromatic objectives of 16 mm. (f in.), 8 mm. 

 (1 in.), and 4 mm. (^ in.) dry, and 3 mm. (^ in.) homo- 

 geneous immersion, made of special glass and having 

 the necessary corrections carried out on a new principle 

 devised by Professor Abbe. 



Compensation eye-pieces, Nos. 4, 8, 12, and 18 so 

 arranged that they multiply the image formed by the 

 objective by an amount corresponding with these num- 

 bers, and also that as each one is successively placed in 

 the tube the object remains in focus. 



E. 192 and 193. 1888. Made by G. Zeiss, Jena. 



C. SIMPLE MICROSCOPES. 



35. Dissecting microscope ; upright pillar with very 

 small stage ; rack and pinion adjustment ; two lenses 

 which swing into and out of position ; plane mirror ; 

 condenser fixed to the stage ; mahogany case with live 

 box and forceps. 



Exhibited by P. Harris $ Go. 1888. 



Price 10s. 6d. 



36. Coddington lens in nickel mount. 



Exhibited by Pastorelli $ Go. 1860. Price 5s. 



37. Simple arrangement for examining microscopic 

 objects contained in water or other liquids. Probably 

 part of a set of apparatus used for the instruction of the 

 royal residents at Kew. 



E. 20. 1891. Given by W. T. ThiseUon Dyer, F.E.S. 



D. OPTICAL ACCESSORIES. 



38. Substage condenser with 1 inch achromatic objec- 

 tive made by direction of Dr. Wallich. 

 Lent by Govt. Grant Committee of the Royal Society. 1889, 



