THE COMPOUND MICEOSCOPE. 95 



any direction, and so move the stage the reduced quantity, which, 

 in this case, is as one to six. To enable both sides of the stage- 

 plate, h, to move simultaneously, a parallel motion is added, 

 one of the rods of which is seen at w. Whichever way the 

 baUs and sockets move, the stage-plate, h, obeys their mo- 

 tions, and an observer, with the lever in his hand, may foUow 

 the course of any living object. By an error on the part of 

 the artist, fig. 47 is reversed; the lever should be on the right 

 hand. 



To the lower part of the stage is fitted either one of Mr. 

 Varley's dark chambers, or a Wollaston condenser: Mr. 

 Varley prefers the former, as it is more free from colour. At 

 the lower part of the tube, z, into which the rod, d, slides, is 

 seen the mirror; this, as in Mr. Powell's microscopes, is 

 mounted on a bent arm, and, if necessary, by means of a 

 sliding tube, may be moved up or down the tube, z. The 

 tube of the compound body, 1, is mounted by means of a hollow 

 case or trough, 2, having two arms, 7, upon the rod, d, and is 

 kept firmly fixed in any position by means of a screw with a 

 milled head and a bent spring. To the back of the tube is 

 soldered a rack, this is connected by two saddle-pieces, 3, with 

 a bar, 4. A pinion, held in a spring, made of plate-brass, as 

 wide as the trough, is attached by a screw to its inner side, 

 and the milled heads which turn the pinion are seen on each 

 side of the same trough ; by either of these the coarse adjust- 

 ment is efiected. Through the upper part of the tube, 1, slides 

 that part of the compound body which supports the eye-piece, 

 and to the lower end is attached a bent arm, through which 

 works the milled head-screw, 12 ; above this is another bent 

 arm connected with a smaller sliding tube bearing the object- 

 glasses ; within this tube is a spiral spring, the action of which 

 causes the tube to be pushed out, but this is prevented by 

 the long arm of a lever, 11, against which the screw presses. 

 When the screw therefore is turned, the arm, 11, is either 

 raised or depressed slowly, and by this the fine adjustment is 

 accomplished. A condensing lens, 27, is most conveniently 

 held by a moveable arm ; the curve, 29, and joint, 30, allow it to 

 be moved to or from the stage, either vertically or horizontally. 



