GENERAL DIRECTIONS. 5 



show clearly, do not strain the eye to see it, but change 

 the focus by the fine adjustment. 



4. Study the microscope until you are familiar with 

 the names and uses of the various parts. 



5. Make a sketch of the microscope and carefully label 

 the parts. 



NOTE. The Leitz microscope and only the lenses that are most 

 frequently used are here described. The general description, how- 

 ever, would apply to any other manufacture, but each kind has its 

 own system of magnification. 



In the microscopes made by the Bausch and Lomb Optical Co., 

 the objectives and eyepieces are designated by their focal distances. 

 The low-power objectives range from a focal distance of 3 inches 

 (the lowest) to inch. The higher objectives range from a focal 

 distance of ^ inch to ^ inch (the highest). The eyepieces range from 

 a focal distance of 2 inches (a low power) to \ inch (a high power). 



C. The Sketches and Records of Experiments. 

 I. SKETCHES. 



All the more important observations should be recorded 

 by sketches. 



a. The outlines may be first traced lightly. 



b. When all the parts are drawn, the outlines may be 

 darkened with a hard pencil (H H H H) and the various parts 

 made clear when necessary by the use of colored crayons 

 or water colors. 



c. Draw on a large scale and label neatly at the side of 

 the drawing. 



d. Do not shade your drawings so as to conceal the 

 essential parts. 



