THE MICROSCOPE AND HOW TO USE IT. 23 



of a soft piece of wash-leather, which should on no account be 

 used for any other purpose. Specimens should invariably be exa- 

 mined, first with the lowest power and then with the next higher^ and 

 so on until the highest power is reached, using with the low powers 

 a medium-sized diaphragm, and a somewhat smaller one with the 

 higher powers. Before placing or removing specimens, the objec- 

 tive is always to be withdrawn some distance from the stage by 

 drawing the microscope-tube upwards with a gentle turn of the 

 coarse adjustment-screw. When placed in position, the object 

 may be brought to a focus by gently lowering the tube with the 

 coarse adjustment till the specimen is fairly in view, and then, 

 slightly turning the fine adjustment-screw until a clear and distinct 

 image is obtained. Care is to be taken that this fine adjustment- 

 screw is not turned too much to the left so as to rise far out from 

 the stand, nor too much to the right and so become fixed. 



It is best to accustom oneself to working with both the left and 

 right eye, at the same time keeping open the one not directly in 

 use. By this means the eyes become less tired^ and after a little 

 practice the whole attention will be thrown upon the object under 

 examination. This plan is also of great assistance in making 

 sketches of the preparations. It is a good plan to make drawings 

 of all objects under examination. Our method of procedure is to 

 place the sketch-book or drawing-paper on the right-hand side of 

 the microscope level with the stage, and to draw a faint outline of 

 the object with an "H." pencil, and afterwards carefully finish 

 with the " H.B.," shading where required ; coloured chalks or 

 water-colours may be used. The latter, however, we consider 

 preferable. 



All drawings should be made of the apparent size as seen in 

 the microscope, and a note to this effect should always be made at 

 the left-hand corner of the paper. It should state the power of 

 the objective, number of eye-piece, and degree of enlargement; 

 e.g.^ I in. A x 25, ^ in. A x 120, as the case may be. 



The degree of magnification may always be ascertained by 

 substituting a micrometer slide for the actual slide, and by drawing 

 a few of the lines on the paper at exactly the same distance apart 

 as they appear in the microscope; thus, if 10 lines which are on 

 the micrometer plate ^^ of an inch apart appear to occupy one 



