234 USE OF THE MICROSCOPE. 



be required for it to be completed at one sitting, the paper 

 should be fixed to the table by a weight 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 ; there 

 will then be no risk of the shifting of the paper, as when the 

 wood is moved, both microscope and paper will move with it. 



In all sketches made by the camera, certain things must 

 be borne in mind ; the eye, when once applied to it, should be 

 kept steadily fixed in one position, and if the sketches are to 

 be reserved for comparison with others, the distance between 

 the paper and the camera should be always the same. A 

 short rule or a piece of wood may be placed between the paper 

 and the under surface either of the compound body or the arm 

 supporting it, in order to regulate the distance, unless the joint 

 be furnished with a stop, as the size of the drawing made by 

 the camera will depend upon the distance between it and the 

 paper. It is also very desirable, before the camera is removed, 

 to make a tracing in some part of the paper of two or more of 

 the divisions of the stage micrometer, in order that they may 

 form a guide to the measurement of all parts of the object. 

 Some persons cover the whole of the drawing over with 

 squares, to facilitate not only the measurement, but in order 

 that a larger or smaller drawing may be made from it than 

 that given by the camera. It must be recollected that an 

 accurate outline is the only thing the camera will give, the 

 finishing of the picttire will depend entirely upon the skill of 

 the artist himself. 



Uses to which the Camera Lucida may be applied. — Besides 

 the valuable assistance rendered to the draughtsman by 

 this instrument, its application to micrometry is also of no 

 small utility ; the method before described at page 223, will 

 answer for all purposes. If it be required to make a very 

 large but accurate diagram of any microscopic object, a true 

 outline of it may be drawn by following these directions. A 

 large sheet of paper, attached by pins to a drawing-board, 

 having been laid on the floor, and the microscope placed hori- 

 zontally, with its compound body projecting as far over the 



