E. Nose- Piece, an extra piece which is attached 

 to the lower part of the tube to hold the objective. 



Society Screw, a standard screw which is cut 

 into the* nose-piece and is called so from the fact that 

 it was first recommended by the Royal Microscopical 

 Society of London. It is also called the universal 

 screw and is in general use in this country. 



F. Objective, contains the object lenses, is 

 screwed into the nose-piece and is called so because 

 it is nearest the object. It is the most important of the 

 two optical parts (of the microscope proper) and upon 

 its perfection the distinctness of the image and there- 

 fore the value of the instrument almost entirely 

 depends. 



G. Eyepiece or Ocular, the remaining optical 

 part, and called so because it is nearest the eye. It 

 magnifies the image given by the objective. This and 

 the objective will be fully treated later on. 



H. Draw-Tube, the inner tube of the body which 

 moves in the outer sheath and which receives the eye- 

 piece. It permits adjustment for different tube lengths 

 and variations in magnifying power. 



I. Collar, a ring which is attached to the draw- 

 tube and is usually provided with a milled or knurled 

 edge. 



3 1 



