93 



By fitting a drum-shaped adapter to these micrometer eye-pieces lateral 

 adjustment of the micrometer scale, or of an index (see under Index Eye-pieces, 

 p. 108), becomes also possible. When thus fitted, they are called "Drum Eye- 

 pieces With Micrometer" and may also consist of either the HUYGENIAN 

 eye-pieces 2 or 3 or compensating eye-piece 6. 



Prices of Micrometer Eye-pieces for achromatic objectives with HUYGENIAN eye-piece 

 2 or 3 as desired: 



Price : Code-words : 



No. 120: ivith drop-in micrometer scale Marks 18. . Pavonazo. 



121: micrometer laterally adjustable by means of a screw 



(Drum Eye-piece ivith Micrometer) ,, 40. . Pavorde. 



Ptices of Micrometer Eye-pieces for apochromatic objectives 

 with compensating eye-pieces 6: 



No. 122: with drop-in micrometer scale ,, 37. . Pavura. 



123: micrometer laterally adjustable by means of a screiv 



(Drum Eye-piece ivith Micrometer) ,, 5j. . 



The prices of micrometer eye-pieces, Nos. 121 and 123 include cases. 



For prices of PLAGGE'S Projection Micrometer Eye-pieces refer 

 to list of prices at end of catalogue, p. 131. 



For very exact measurements a *Screw Micrometer Eye -piece is 



required. This form of instrument as constructed by us is shown in Fig. 52. 

 It consists of a RAMSDEN eye-piece of about 20 mm ( 3 /4 in.) focal length - 



Fig. 52. Screw Micrometer Eye-piece, No. 124. 



Sectional elevation and plan view. ( 2 / 8 Full Size.) 



