OF THE MICEOSCOPE. 



107 



Fig. 20. STBAIGHT NOSE-PIECE. 



Double Nose-Piece. This is one of the most useful 

 accessories that the microscopist can possess. The result to be 

 obtained, and the method of accomplishing it are obvious. The 



nose-piece screws on to the 

 nose, or lower end of the body 

 of the microscope, and is 

 fitted to receive two objec- 

 tives of different powers, 

 either one of which maybe 

 brought into action by simply 

 turning the nose-piece. In 



this way a low power may be used for finding objects and ex- 

 amining them as a whole, while the details may, without 

 trouble, be subjected to an 

 object-glass of much higher 

 power. Two forms of the 

 nose-piece are in use. The 

 older form is straight, as in 

 Fig. 20; the later form is 

 bent, as in Fig. 21. The lat- 

 ter form is altogether the most 

 convenient. Nose-pieces ca- 

 pable of receiving three or 

 four objectives have been con- 

 structed, and a very old mi- 

 croscope, at one time in our 

 possession, had a nose-piece 

 with eight objectives! The 

 modern nose-piece, so ar- 

 ranged as to be capable of 



carrying the best objectives, is Fi S- 21. BENT NOSE-PIECE. 



the invention of Mr. Brookes. 



ILLUMINATION SOUKCES OF LIGHT. 



Sun Light. It is generally acknowledged that the best 

 light for microscopical purposes is that of the sun; not direct 

 sunlight, however, for this is altogether too intense, but sun 



