INTRODUCTION TO OPTICS. 

 Fig. 41. 



xcix 



the lens itself being placed at such a distance from the opposite wall 

 that an image may be accurately formed upon it ; the image E F there- 

 fore will be represented on the opposite wall in the same manner as 

 the landscape was in the camera obscura with this difference, that it 

 will be magnified, instead of being diminished, because it is farther from 

 the lens than the object A B ; while the representation of the landscape 

 was diminished, because it was nearer the lens than the landscape was : a 

 lens, therefore, answers the purpose equally well, either for magnifying or 

 diminishing objects. In this state, the image produced by the solar 

 microscope is faint and indistinct, a very small ray of light being diffused 

 over a prodigiously magnified image ; but if the aperture be enlarged, so 

 as to admit a more considerable pencil of rays, and a lens X Y (Jig. 42) 



Fig. 42. 



placed in it to bring it to a focus on the object AB, the image will be 

 much more distinct. There is but one thing more required to complete 

 the solar microscope, which is a small mirror, PQ (placed on the outside 

 of the window-shutter), which receives the incident rays, S S, and reflects 

 them on the lens X Y. This microscope can be used only when the sun 

 shines, and is adapted to transparent objects. Very minute objects, such 

 as are viewed in a microscope, are generally transparent; but when 

 opaque bodies are to be exhibited, a, second mirror M N (Jig. 43) is used 

 to reflect the light on the side of the object next the wall : the image is 

 then formed by light reflected from the object, instead of being formed by 

 rays transmitted by it. A magic lantern is constructed on the same 

 principle with tlys difference, that the light is supplied by a lamp instead 



