:,::( ; 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



(2) Eye-pieces and Objectives. 



Winkel's Eye-piece with Screw Micrometer and Graduated Glass 

 Diaphragm.* — Fig. (iO gives a general view of this eye-piece, which can 

 lie used for approximate measurements as well as for readings of great 

 precision. It is provided with a clamping screw to fix it firmly to the 

 tube of the Microscope, and an adjustable eye-lens for focusing the scale. 

 The scale itself is mounted on a plate (fig. 61), which is movable in a 

 lateral direction by a screw, the spring serving to keep the plate always 

 in contact with the screw, which has five threads to the millimetre and 



Fig. 60. 



Fig. 61. 



is fitted with a drum divided into 100 parts ; each interval of the drum 

 is equal, therefore, to a lateral displacement of the scale of -j^ mm. 



This combination of scale and screw micrometer has been chosen (at 

 the suggestion of the late A. Kochf) in preference to screw and web 

 usually employed, as it gives a ready means of obtaining the exact 

 measurement of objects subtending a number of divisions of the eye- 

 pieces scale, the fractional part only of an interval having to be deter- 

 mined by means of the screw. 



* R. Winkel, Gottingen Catalogue, 1911, p. li (2 figs.). 

 t Zeitschr. wiss. Mikrosk., vi. pp. 33-35. 



