102 THE MICROSCOPE. 



Lucida with the microscope : The first step to be taken, after the ob- 

 ject about to be drawn has been properly illuminated, adjusted, and 

 brought into the centre of the field of view, is to place the compound 

 body of the microscope in a horizontal position, and to fix it there. 

 The cap of the eye-piece having been removed, the camera is to be slid 

 on in its stead : if the prism is properly adjusted, a circle of white 

 light, with the object within it, will be seen on a piece of white paper 

 placed on the table immediately under the camera, when the eye of the 

 observer is placed over the uncovered edge of the prism, and its axis 

 directed towards the paper on the table. Should, however, the field 

 of view be only in part illuminated, the prism must either be turned 

 round on the eye-piece, or revolved on its axis, by the screws affixed to 

 its frame- work, until the entire field is illuminated. The next step is 

 to procure a hard, sharp-pointed pencil, which, in order to be well seen, 

 may be blackened with ink round the point ; the observer is then to 

 bring his eye so near the edge of the prism that he may be able to see 

 on the paper, at one and the same time, the pencil-point and the image 

 of the object. When he has accomplished this, the pencil may be moved 

 along the outline of the image, so as to trace it on the paper. How- 

 ever easy this may appear in description, it will be found very difficult 

 in practice ; and the observer must not be foiled in his first attempts, 

 but must persevere until he accomplishes his purpose. Sometimes he 

 will find that he can see the pencil-point, and all at once it disappears : 

 this happens from the movement of the axis of the eye. The plan 

 then is to keep the pencil upon the paper, and to move about the eye 

 until the pencil is again seen, when the eye is to be kept steadfastly 

 fixed on the same position until the entire outline is traced. It will be 

 found the best plan for the beginner to employ at first an inch object- 

 glass, and some object, such as a piece of moss, that has a well-defined 

 outline, and to make many tracings, and examine how nearly they 

 agree with each other; and when he has succeeded to his liking, he 

 may then take a more complicated subject. If the operation is con- 

 ducted by lamp-light, it will be found very advantageous not to illumi- 

 nate the object too much, but rather to illuminate the paper on which 

 the sketch is to be made, either by means of the lamp with the condensing 

 lens, or a small taper placed near it. When the object is so compli- 

 cated that too much time would be required for it to be completed 

 at one sitting, the paper should be fixed to the table by a weight y or 

 on a board by drawing-pins. An excellent plan to adopt is to fix the 

 microscope on a piece of deal about two feet in length and one foot in 

 breadth, and to pin the paper to the same j there will then be no risk 



