ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



49. : 



from convergent to parallel light. By a connecting-piece applied to the 

 tube end, the objective is centred on the rotation centre of the rotatory 

 object stage, which is graduated into 860° with a vernier. The stage 

 has orientation marks, and there are two drum-graduations at the side 

 of the stage for reading off lateral movements, which can be performed 

 up to 20 mm. The Nicol polariser can, after the removal of the iris 

 carrier, be drawn out of the screw from below, and an illuminating 

 apparatus with iris can be inserted instead. The zero of this Nicol is 

 marked, as well as the 90°, 180° and 270°. The analyser, in a metal 

 collar, is placed above the ocular, and rotates on a rim rigidly connected 

 with the ocular mount. This rim is graduated into 360°. On the front 

 side of the tube is a flap, which can be opened or closed, and through 

 which access can be had to the inner tube. In this flap is a slit for the 

 Bertrand lens, and under the lens is an iris for the sharp delimitation of 

 the interference figures. 



Leitz' Demonstration-Microscope.* — This instrument, shown in 

 fig. 87, is intended for weak and medium magnifications. The stage is 

 rectangular with rotatory diaphragm. The 

 tube-adjustment is by push action and a 

 clamp-ring. A fine adjustment, condenser, 

 and iris can be adapted if desired. 



Leitz' Mineralogical Stand No. Il.f — 

 The instrument (fig. 88) now issued with this 

 title (maker's series, No. 38) is a somewhat 

 simplified and smaller form of the same 

 firm's Mineralogical Stand No. I., previously 

 described in this Journal,! their former 

 No. II. having now become Stand No. III. 

 The coarse adjustment is by rack-and-pinion, 

 the fine by micrometer screw, a division 

 signifying a movement of 0'01 mm. The 

 condenser, iris and polariser can be raised 

 and lowered by a lateral screw. A three- 

 limbed condenser allows the convenient 

 observation of the axial images in the 

 Microscope ; both the upper lenses can be 

 put out of action by a lever. By means of 

 an intermediate piece applied to the tube- 

 end the objective can be centred on the 

 centre of the rotatory object-stage, which is 

 graduated into 360° and fitted with a vernier. 

 The stage also has graduations for orienta- 

 tion. The polarising Nicol can after the Fig. 87. 

 expansion of the iris be drawn out 



from underneath. The zero of this Nicol is marked, as also the 90®, 

 180°, 270°. The analyser rotates on a disc, whose circumference is 



* Catalogue No. 41 (Mikroskope) 1905, p. 51. 



t Tom. cit., p. 63. : J.R.M.S., 1903, p. 758, fig. It;:'.. 



