USE OF THE MICUOSCOPE. 



CHAPTER L 



PBELIMINARY DIRECTIONS. 



All the most complete forms, both of simple and compound 

 microscopes, constructed by our principal makers, together 

 with the optical and other apparatus supplied with them, 

 having now been fully described in the first part of the work, 

 it becomes necessary to enter in detail into the different modes 

 of using the same ; and as the compound instrument is of 

 more general importance and more difficult to use than the 

 simple form, it must first claim our attention. For the 

 better understanding of the different steps in the proceeding, 

 it has been deemed advisable, however, to describe them under 

 separate heads. 



Position. — If day-light is to be employed as the illuminating 

 agent, the spot selected for planting the microscope on should 

 be in all cases a firm steady table, near a window that is not 

 at the time exposed to the direct rays of the sun ; a white 

 cloud immediately opposite to the sun is the point from which 

 the most intense light is given off, and a blue sky in the same 

 situation, or a dark cloud, is that from which the fewest rays 

 proceed. K the instrument is to be used at night, it matters 

 not where the table is placed, but the choice of an illuminator 

 then becomes necessary ; this most commonly is an Argand 

 oil lamp, but a wax light or that of gas or camphine may 

 supply its place. The microscope having the mirror and the 

 rest of the optical part free from dust, being placed upon the 

 table, and an eye-piece having been slid into one end of the 



