6 LABORATORY DIRECTIONS IN 



1. Never focus downward while looking into the microscope as there is 

 great danger thus of driving the objective against the object examined, 

 to the great injury of both. 



2. Never wipe off the ocular or objective with handkerchief, cloth, 

 or anything except lens paper, which will be furnished as needed. 



3. In case the 'ocular or objective cannot be readily cleaned or is 

 injured in any way take it at once to one of the instructors. Do not 

 try to clean it yourself. 



5. Report at once to the instructor any missing parts or injuries to 

 the microscope. 



PREPARED SLIDE OF A PRINTED LETTER 



1. Focusing. Place the 4x ocular and 16 mm. objective in position 

 and adjust the mirror so that the light from the window passes up through 

 the tube of the microscope. Now so place the slide of the printed letter 

 on the microscope that its label may be read (that is, right side up) and 

 the letter is as nearly as possible in the center of the aperture in the stage. 



Lower the tube of the microscope by means of the coarse adjustment 

 until the objective almost touches the cover-glass; then with the eye 

 at the ocular slowly move the tube upward until the letter on the slide 

 appears distinct. 



2. Relation of Object and Image. With the slide held as in (1) 

 make a drawing (on drawing paper) of the letter as seen with the unaided 

 eye, and another drawing of the image made by the microscope. Before 

 making your drawing, refer again to the instructions for labeling draw- 

 ings and plates. 



These drawings should be made of the same size as the image and 

 object respectively. The image may be measured by laying a milli- 

 meter scale across the stage of the microscope at one side, and looking 

 into the microscope with one eye and at the scale with the other. The 

 scale will appear to lie over the image. 



This sheet of drawings is your Plate I. Always follow this style in 

 making up your plates. 



Now using note paper and ink state how the image differs from the 

 object. 



3. Illumination. Note carefully the brightness of the field of vision 

 and the appearance of the letter; it is illuminated by transmitted light. 

 Tilt the mirror and observe the change in the intensity and character of 

 the light. The object is now viewed by reflected light which must be 

 employed for all opaque objects. 



4. Magnification. Determine what combination of ocular and ob- 

 jective gives the lowest magnification, what combination the highest, 

 etc. Make a table showing all the combinations of objectives and oculars 

 arranged in the order of their magnifying power. 



