492 SUMMARY OF CURRENT RESEARCHES. 



MICROSCOPY. 



A. Instruments, Accessories, &c* 

 (1); Stands. 



Koristka's Large Model Mineralogical Microscope.! — This instru- 

 ment (fiir. 85), fitted with the most recent improvements, was constructed 

 under the direction of Professor L. Brugnatelli. 



The upper end of the pillar is elongated, in order to allow the use of 

 auxiliary apparatus, such as a Klein's or Federow's plate. 



The rotatory stage has a diameter of 120 mm., is divided into degrees, 

 and has a vernier reading to 10' and even 6'. It also has rectangular 

 movements, with micrometer adjustments, the milled heads of which 

 J K are divided up to O'Ol mm. and 0-04 mm. respectively. 



The illuminating apparatus has a special fitting for instantly re- 

 moving the condenser, and for changing from convergent to parallel 

 light, or vice versa. 



The polariser is raised by a rack-and-pinion N, and has an iris 

 diaphragm with graduated collar R. The screw-head H is for centring 

 the objectives, and the slit I for a Klein's quartz or other accessory. 



The analyser G is easily thrown out of the field, has a rotation of 9<>° 

 and a graduated scale F. It is supplied with a special lens for main- 

 taining the focal length of the optical system. The ocular tube is moved 

 up and down by rack-and-pinion B ; it has a displacement of 36 mm. 

 and has mm. divisions for marking its position. 



At its lower end it is fitted with a diaphragm D, and also has a slit 

 C, with a Bertrand lens for observing the axial image. 



The upper end of the ocular tube is adapted for the reception of a 

 second analyser, having a circular graduated scale, and also for the 

 insertion of any kind of eyepiece. 



Leitz' Mineralogical Stand No. I.J — This instrument (fig. «6) 

 corresponds in its dimensions to Stand No. I. in the maker's catalogue. 

 The coarse adjustment is by rack-and-pinion ; the fine, by Leitz' new 

 fine adjustment with side-knobs,§ the drum being divided into 100 parts, 

 so that one graduation means a movement of • 001 mm. Condenser, iris 

 diaphragm, and polariser are raised and lowered by a lateral screw. A 

 three-limbed condenser with iris diaphragm facilitates convenient obser- 

 vation of the axial pictures in the Microscope. Both the upper lenses of 

 the condenser can be drawn out by a lateral lever if one wants to change 



* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; (3) Illu- 

 minating and other Apparatus; (4) Photomicrography; (5) Microscopical Optics 

 and Manipulation ; (<!) Miscellaneous. 



t Koristka's Catalogue, No. 12, Turin, 1905, p. 31, fig. 15. 



: Catalogue No. 41 (Mikroskope) 1905, pp. 59-61. 



§ J.R.M.S. 1903, pp. G67. 



