14 The Microscope. 



should be at least 15 or 20 and should include those from 2 to 8 

 inches in diameteri. All instruments, slips, cover -glasses, speci- 

 mens in various stages of preparation, etc., can be kept under them, 

 free from dust and easily accessible, as they are in view. The table 

 should be of medium height — about 2 ft. 6 in. — and firmly set. 



Light. — The table should face a window of ample dimensions, 

 provided with shades to cut off direct sunlight. It makes no differ- 

 ence what exposure the window may have, so that light is admitted 

 in sufficient quantity. The ideal light is said to be that reflected 

 from a white, cumulous cloud ; but as clouds cannot be manufac- 

 tured to order, it is as well to ignore them altogether and, by means 

 of good shades, command a more reliable if not a better light. Arti- 

 ficial light is to be avoided when practicable, especially when work- 

 ing with the microscope. In the latter case it is not only more 

 trying to the eyes, but it renders objects more difficult of study. 

 Colors are not so well defined by it, and even with the use of a good 

 condenser, has a tendency to create shadows in the specimen. All 

 results obtained through the aid of artificial light should be con- 

 firmed by true light. Lamp light is better than gas light, being 

 softer and steadier. The electric light, now being so generally intro- 

 duced into private residences, may prove the best, though the writer 

 has had no experience with it. An ordinary lamp will serve every 

 purpose so long as the light given by it is steady. A bull's-eye 

 lamp furnishes a most satisfactory light for use with the microscope, 

 especially when high-power objectives are employed. Among the 

 best of these is one manufactured by J. W. Queen & Co., of Phila- 

 delphia, called the "Acme." It is simple and cheap and answers 

 every purpose. To correct the color and render the rays of artifi- 

 cial light more parallel several expedients have been proposed. One 

 of the best of these is a glass globe, from 4 to G inches in diameter, 

 filled with a solution of ammonia- sulphate of copper. This solution 

 is made by dissolving a quantity of sulphate of copper in water and 

 adding a few drops of ammonia. This will give a beautiful blue 

 color. The globe thus filled can be placed between the light and 

 mirror. Somewhat more simple, though not so effective, is a blue 

 slip placed u.nder the slide. When iising the microscope, never 

 employ any more light than is necessary to give a distinct view of 

 the object. As the reader is supposed to be familiar with the use of 

 diaphragms, nothing need be said on this point. 



•The Microscope. — For actual work the microscope should be of 

 the simplest construction possible. The numerous patent appliances, 



