Microscopical Essays, ^~ 



the much larger angle DAE (the fame as the angle f A g). And 

 therefore, the dart B C will appear fo much magnified, as to ex- 

 tend in length from D to E. 



The objeft, when thus feen diftin&Iy, by means of the fmall, 

 Jens, appears to be magnified nearly in the proportion which 

 the focal diftance of the glafs bears to the diftance of the objects, 

 when viewed by the naked eye. 



To explain this further, place the eye clofe to the glafs, that 

 as much of the object may be feen at one view as is poffible ; 

 then remove the object to and fro, till it appears perfectly 

 diftinft, and well defined ; now remove the lens, and fubftitute 

 in it's place a thin plate, with a very fmall hole in it, and the 

 object will appear as diftinct, and as much magnified, as with the 

 lens, though not quite fo bright ; and it appears as much more 

 magnified in this cafe, than it does when viewed with the naked 

 eye, as the diftance of the object: from the hole, or lens, is lefs 

 than the diftance at which it may be feen diftinctly with the naked 

 eye*. 



From hence we fee, that the whole effect of the lens is t© 

 render the object diftinct, which it does by aflifting the eye to 

 increafe the refraction of the rays in each pencil ; and that the 

 apparent magnitude is entirely owing to the object being feen fa 

 much nearer the eye than it couldbe viewed without it 



Single microfcopes magnify the diameter of the object, * as we 

 lave already ftiewn, in the proportion of the focal diftance (to the 



limits* 



* Cyclopedia art micxofcop©-* 



