one of them may be brought to lie at the lower end of the tube. 

 The tube is really double, one tube being telescoped within another. 

 By holding the body firmly in the left hand and taking hold of the 

 projecting brass ring just below the eye-piece with the right, the 

 inner tube may be drawn out some distance, thus lengthening the 

 body and increasing the magnification. The length of the tube 

 without lenses and nose-piece is 150 mm. and it can be drawn out 

 to 195 mm.; with the nose-piece the tube is 10 mm. longer. A table 

 of magnifications of the different lenses with a given tube length 

 is found on the inside of each case. 



B. USE. i. Reflect light, from white clouds if possible, upon 

 the object. \Yhere all the light is needed, use concave mirror; 

 where light is intense and a low magnification is required, use 

 plane mirror. 



2. Use smaller diaphragms with higher powers. 



3. To focus lenses upon an object, use first the coarse, then the 

 fine adjustment; the former movement is by means of a rack and 

 pinion. The rack is the toothed plate along the back of the tube, 

 the pinion is a small cog wheel which fits into the rack and is 

 turned by the two milled wheels on each side of the tube. The fine 

 adjustment is by means of a milled serein back of the pinion. If 

 the fine adjustment screw is turned in the direction in which a 

 clock's hands move the tube is lowered, turned in the reverse di- 

 rection it is raised. In using a high power turn the tube down 

 nearly to the object and, then, while looking through the microscope, 

 bring the object into focus by slowly turning the tube upward. 

 Never focus down upon the object, since by this method there is 

 danger of crushing the lens into the object. Keep one hand on the 

 fine adjustment when looking at an object and vary the focus con- 

 stantly to bring all the fine details of structure into view. 



4. Do not use higher power objective without cover glass over 

 object examined. 



5. Always use the lower power before the higher one ; and 

 always use the lowest possible power sufficient for distinct vision. 



6. Do not touch lenses with fingers. If the field is blurred or 

 the object dim either the cover glass or the lenses are at fault. If 

 the cover glass is dirty remove it and clean it; if the fault is in 

 the eye-piece the particles of dirt revolve when the eye-piece is 

 rotated. If the field is still dim the objective is dirty and must be 

 removed and cleaned. In cleaning the lenses never use anything 

 but clean tissue paper supplied for that purpose. If necessary, the 



