THE MICROSCOPE AND ITS ACCESSORIES. 



(A.) Mechanical Parts. It should bo quite stable, so that it 

 cannot be readily upset. To this end the stand should be solid, and 

 either of the tripod (fig. 15) or horse-shoe pattern (figs. 9, 10). Very 

 good stands of the tripod pattern are made by Messrs. James 

 Swift & Sons (fig. 15) and Messrs. Crouch. Fig. 1 5 has a glass stage, 

 the body-tube is cloth-lined, which gives a smooth and steady action. 

 The stage should be at a convenient height, so that when the ulnar 

 edge of the left hand is resting on the table, the thumb and fore- 

 finger of the same hand can conveniently grasp find move the slide on 

 the stage. The stage itself should be a little broader than the length 

 of the slide. The slide can be fixed on the stage by means of two 

 brass clips, which are fitted into holes at 

 the two posterior angles of the stage. 

 The pillar of the microscope may be fitted 

 with a joint to enable the instrument to 

 be inclined, if desired; but of course 

 this cannot be used when fluids are being 

 examined ; still in many instances it is 

 convenient (figs. 10, 14). Fig. 16 shows 

 a convenient form made by Hartnack of 

 Potsdam, and one very extensively used 

 by students. 



Itis highly inconvenient tohave to screw 

 and unscrew a lens every time a change 

 of lens is required. This is obviated by 

 using a nose-piece or revolver (figs. 10, 

 14), which is screwed to the lower end 

 of the tube of the microscope. The high 

 and low powers are fitted to this frame- 

 work, and can be rotated under the tube 

 as they are required. Xose-pieces are 

 made for attaching two or three (figs. 10, 



/VKir>r>H'-uoe and tVmvnnn Vio 

 Objectives, and tney can L 



iidapted to any microscope. 



One must be cautious in using a nose-piece, and take care to raise 

 the tube high enough to allow the objective to revolve without touch- 

 ing the cover-glass, which is especially apt to happen on using a high 

 power after a low power, the lenses not being of the same length. 



Test the mechanical parts that they are all solid and work well. 

 "Raise and lower the tube by means of the fine adjustment, and do 

 this to the full extent of the threads on the screw, noting parti- 

 cularly if there is any lateral movement of the tube while this is 

 being done. 



(B.) Optical Parts. Sec that all the parts arc properly centred by 

 looking through the tube after removal of the eye-piece. Put on 



FlG. 16. Stand III. of Hartnack, 

 with joint ami condenser. 



