Microscopic discoveries. 83 



globule of glass, fixed in a thin plate of metal, so that the 

 middle of it may be directly over the centre of an extremely 

 small hole made in the plate. 



The compound microscope consists of at least two lenses, 

 by one of which an image is formed within the tube of the 

 microscope ; and this image is viewed through the eye-glass, 

 instead of the object itself. The solar microscope is a kind 

 of camera obscura, which, in a darkened chamber, throws 

 the image on a wall or skreen. It consists of two lenses 

 fixed opposite to a hole in a board or window-shutter. There 

 is also a plane reflector or mirror placed without, which may 

 be so regulated as to throw the sun's rays upon the outer 

 Jens". A magic lantern is constructed on the same prm- 

 ciples. The light is supplied by a lamp instead of the sun, 

 and it is used for magnifying paintings on glass, and throw- 

 ing their images upon a white skreen in a darkened chamber. 



Questions. — 1. In what ways may sight be defective .' 2. For 

 what are spectacles intended ? 3. How do they assist eyes that are 

 too flat ? 4. Too convex or round ? 5. Why do some persons bring 

 objects close to tiieir eyes, and others hold them at a distance ? 6. 

 What are microscopep ^ 7. Sin^^le microscopes ? 8. How is their 

 magnifying power calculated ? 9. Describe the compound microscope. 

 10. Solar microscope. 11. Magic lantern. 12. Look on fig. 35. and 

 describe the single microscope. 13. On fig. 34. and describe the com- 

 pound microscope. 



LESSON 38. 



Microscopic Discoveries. 



Miniature, (pronounced min'e-ture,) representation in a small 



compass. Fil'ament, a slender thread. 

 Ped'icle, a footstalk. Animal'cule, a small animal. 

 Con'ical, consisting of a circular base or bottom and ending in a 



point. 

 Tissue, (pron. tish'Q,) a substance interwoven with threads, or 



va-riegatcd. 



Tjje microscope has opened to us a new world of insects 

 and Vegetables ; it has taught us that objects, invisible to the 

 naked eye, exist, having figure, extension, and different 

 parts ; some examples of which we shall produce, that we 

 may have more reasons for admiring and praising the wis- 

 dom and power of God. A grain of sand when examined 

 Dy the eye appears round, but with the help of a glass we 



