ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



1051 



Fig. 219. 



Fine-Adjustment to the New Zeiss Stands.* — Dr. S. Czapski 

 gives a short account of the simplified construction of the fine-adjust- 

 ment as now adopted for the Zeiss Microscopes. 



The triangular bar C, fig. 219, is screwed firmly to the stage. On it 

 moves a hollow piece B, which is connected inseparably with the arm 

 A carrying the tube. The accuracy of the fitting of B and C is 

 insured by the brass plate D, which is fastened to B by a pin. At 

 its upper end C is cut away for 

 about 15 mm. and B hollowed 

 out at the corresponding place 

 so that space is obtained for a 

 spiral spring. This spring 

 bears below against the hol- 

 lowed out part of B, its upper 

 end being connected with the 

 projections of a piece E, 

 screwed into C. The piece B 

 is closed above by the brass 

 cap F, in which is the female 

 screw. To the top of the 

 micrometer screw is fitted a 

 bell-shaped head, and at its 

 lower end is a small nut for 

 preventing inadvertent extrac- 

 tion of the screw. The lower 

 end of the screw is rounded 

 off and bears against tho flat 

 surface of a hard steel cylinder 

 let into E. The space allowed 

 for the play of the screw is 

 only 5 mm., but this is suffi- 

 cient for all practical purposes. Notwithstanding the relatively long 

 female screw (which guarantees safety of movement and slight wear 

 and tear), the fine-adjustment screw is on the whole rather short and 

 correspondingly firm. The binding screw at the back of B serves to 

 fix B in any desired position (during transport, &c), and thus to 

 prevent the screw mechanism from injury. 



How the apparatus works is evident from the fig. "When turned 

 the micrometer screw remains in the same place, bearing against C. 

 The female screw on the other hand moves over it, raising or lowering 

 the tube-carrier B A connected with it. By its own weight A B 

 counteracts the rise, and thus supplies the place of the strong spiral 

 spring formerly employed. The weak spring here adopted acts in the 

 same direction as the weight of A B, and serves to assist the latter 

 when the upper part of the Microscope is placed horizontally. The 

 micrometer screw is a left-handed one, in order that when the screw 

 head is turned to the right the tube, as is usual, may sink. 



* Zeitschr. f. Wiss. Mikr., iii. (188(3) pp. 207-9 (1 fig.)- 



