THE MICROSCOPE AND ITS PARTS. 41 



single sight of the bubbles themselves. At times they 

 become entangled in the parts of an object in such num- 

 bers as to interfere with its examination. In these cases 

 nothing can be done except to lift the cover on the 

 point of the needle, and slowly lower it, or remove it 

 entirely, add more water, and reapply it carefully. In 

 appearance the bubbles are usually circular, with a broad 

 black border which varies in width and depth of color 

 as the objective is raised or lowered. Near the margin 

 is a bright ring, and in the centre a bright spot. They 

 often float about, and this movement adds much to the 

 wonder with which the beginner usually regards them. 



If the student will have a note-book in which to jot 

 down his observations, or to keep a list of the objects 

 examined, it will not only aid him in forming habits of 

 accurate observation, but will be of great interest when 

 he has become an accomplished microscopist. The en- 

 try may be very simple, and may be made to serve as a 

 memorandum of items to refresh the memory. Here is 

 an example from a boy's note-book: "June 15, 1884 

 Came across a pool near the toll-gate with the 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 quite artis- 

 tic they will help you to remember, and a collection 



