ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 109 



MICROSCOPY. 



o. Instruinents, Accessories, &c.* 



(1) Stands. 



Fasoldt's *' Patent Microscope." — Mr. C. Fasoldt, the well-known 

 ruler of fine lines, has devised the Microscope shown in fig. 1. 



The peculiarities of the construction are (1) the combination of the 

 coarse- and fine-adjustments in one mechanism, which is shown in 

 fig. 2, "intended to prevent the breaking of objects and injury of 

 objectives through the accidental moving of the tube " ; (2) the vertical 

 illuminator, in which by a pair of plates opening angularly by the 

 rotation of a cam and a single diaphragm plate, pivoting together or 

 separately in front of a fixed quadrangular aperture, the light can be 

 variously regulated. The glass disc reflector is attached to a bar, which 

 can be withdrawn for cleaning or replacing by turning the milled-head 

 cap in front. It can also be inclined as well as moved out of the field 

 of view by pulling the bar through the milled-head cap, when the disc 

 lies in the piece of tubing on which the cap fits ; (3) the changing 

 nose-piece applied below the vertical illuminator, by which the objective 

 can be attached or released by the action of a trigger-piece on a sliding 

 tooth, the inner edge of which has the Society screw-thread, and presses 

 the screw of the objective against two similar but fixed teeth opposite ; 

 and (4) the fixed stage-ring has a deep groove round the outer edge, in 

 which the upper plate rotates by means of two short pins on the inner 

 edge of an overlapping flange, two diametral slots in the fixed ring 

 enabling the upper plate to be removed. 



The combined coarse- and fine-adjustments are shown in fig. 2. At 

 the back of the body-tube slide is fixed a short screw-socket, through 

 which a long coarse-threaded screw passes, the rotation of the screw 

 causing the socket, and with it the body-tube, to move up or down. 

 Near the lower end of the screw is fixed a small pinion with spiral teeth, 

 in which a similar but much larger pinion engages for the coarse- 

 adjustment, raising or lowering the body-tube somewhat slowly, after 

 the manner of worm-wheel and tangent-screw mechanism. The screw 

 has a plain cylindrical fitting at each end, by which the small pinion is 

 kept in close contact with the larger one. 



Mr. Fasoldt claims for this system of coarse-adjustment the impossi- 

 bility of any running down occurring by the accidental concussion of 

 the body-tube, as the mechanism remains locked unless set in motion by 

 the milled heads. 



For the fine-adjustment a long bent lever is applied to the lower end 

 of the coarse-adjustment screw, so as to raise it through a space of about 

 1/8 in. against the downward pressure of a short spiral spring encircling 

 the upper end, the great difference in the size of the pinions permitting 

 this range of motion without disengaging the teeth. The lever is acted 

 upon at the back by a milled-head micrometer-screw. 



Mr. Fasoldt writes that he uses the illuminator in the following 

 way : — 



" When the Microscope is in position and the object on it, first find 



* This Bubdivi8ion contains (1) Stands; (2) Eye-pieces and Objectives; (3) Illu- 

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

 and Manipulation ; (6) Miscellaneous. 



