THE FINE ADJUSTMENT 



I/I 



130). That this is an advantage of a very high order if experience 

 proves it to be a practical method there can be no doubt. More- 

 over, the weight which this newly arranged micrometer screw has 

 to lift is, as the firm informs us, only one-fifth of that which was borne 

 by the older form, and there are special arrangements made to pre- 

 vent this delicate construction from being overscrewed either wav. 



The mechanical stage of this microscope has some features worthy 

 of note. It will be seen that the milled heads which work the stage 

 are on Turrell's plan, but the outer head gives transverse movement 

 to the stage plate instead of verti- 

 cal movement. The pitch of tin-- 

 screw on this pinion is fine, so that 

 the motion is slow. The vertical 

 movement which is actuated by the 

 inner pinion head is on altogetln r 

 a novel plan. The motion is one in 

 arc, this stage plate being pivoted 

 on the left-hand side ; the circular 

 portion on the right-hand side 

 has rack teeth cut in it into which 

 a pinion is geared. This pinion 

 has a toothed wheel fixed to it. 

 which engages an endless screw 

 attached to the pinion that carries 

 the inner pinion head. 



The speed of the object at the 

 centre of the stage is about half 

 that of the rack, because the 

 object is placed about halfway 

 between the rack on the right and 

 the pivot on the left hand side of 

 the stage. 



The stage is concentric with 

 simple non-mechanical rotation : it 

 can be clamped in any desired po- 

 sition by a small screw at the side 

 of the stage (not shown in the 

 figure). 



We may now describe the ex- 

 ceedingly simple, and as we think 

 beautiful because essentially prac- 

 tical, fine adjustment invented by 

 Reichert, which we believe will 

 prove itself the most useful and 

 conservative adjunct ever devised 

 to make the Continental stand of service for high -class work with- 

 out increasing its expense or i educing its value in ordinary work. 

 It consists in adapting in a very ingenious manner a lever of the 

 second order to the usual direct acting screw. It will be seen l>\ 

 fig. 131, which represents this part of the microscope open at B 

 and closed as in use at A. The micrometer screw presses on two 



FIG. 188. Swift's patent tint- a 

 (1881 . 



