THE MICROSCOPE AND ITS PARTS. 39 



water colored green, and found the color was caused 

 by a great quantity of Volvox — small green globes 

 rolling about in the water. Volvox is said to be a 

 plant. Wonder if it is ? What are the darker balls 

 inside of some of them ?" He answered all these 

 queries later in his experience. 



If you can draw the microscopic objects that 

 interest you most, although the sketches may not be 

 artistic they will help you to remember, and a collec- 

 tion of such drawings will be as interesting and 

 valuable as a note-book. In talking to friends about 

 microscopic matters, a. single rough sketch will do 

 more to help them understand than many words. And 

 if you can look at the object and make the sketch, 

 you will like it better and do yourself more good than 

 if you bought and used the drawing apparatus called a 

 camera lucida, for sale by the dealers. 



This camera lucida is a glass prism, so arranged 

 that when it is put over the eye-piece, and the 

 microscope is placed in a .horizontal or inclined 

 position, the magnified image seems to be projected 

 on a sheet of paper spread on the table just under the 

 camera, but of course with a space of several inches 

 between them. By placing the eye in the proper 

 position, and looking down towards the table through 

 the edge of the prism, the image and the pencil-point 

 can both be seen at once'and the outlines traced. It 

 is a rather expensive apparatus, and difficult to use 

 without a good deal of practice, but if the reader 

 wants a simple arrangement that can be made by him- 

 self let him try the one shown in Fig. 5. 



From a piece of thin sheet-brass or tin, cut with 

 scissors a strip half an inch wide and long enough for 



