CARE OF Tlll<: MICROSCOPE J 85 



4. Avoid vapor of hydrofluoric acid in the laboratory. 



5. Do not let direct sunlight fall on the mirror and pass 

 through the microscope. 



6. With a water-immersion condenser, keep the top lens and 

 the under surface of the slide free from immersion oil. 



7. Iron-acetocarmine preparations may be sealed with thick 

 dammar solution in xylol, applied with a brush, or with melted 

 paraffin. 



8. Iron-acetocarmine and most other preparations should 

 be kept in the dark, and shielded from the direct sunlight. 



9. The upper surface of the cover-glass is part of the optical 

 system of the microscope, and should be kept as clean as the 

 lower lens of the objective. 



10. The oxygen of the air should be kept from the cedar immer- 

 sion oil, or it rapidly thickens (and its index of refraction rises). 



11. The front lens of a dry objective should be kept optically 

 clean. 



12. The front lens of a water-immersion objective should be 

 free from traces of grease. 



13. Caps to put over the eyepieces during temporary disuse 

 are of importance in keeping off dust. 



14. With the binocular attachment, or the Phoku camera, 

 special precautions must be taken to prevent the microscope 

 toppling backwards. 



15. The prisms of the Greenough require cleaning at definite 

 intervals. 



16. An achromatic hand lens, with the balsam "sprung," can 

 readily be cemented again. 



