306 THE AMERICAN MONTHLY [Nov 



the microscope for many purposes. The compouud mi- 

 croscopes I have before you cost from ten to fifteen dol- 

 lars apiece, according to the powers with which they are 

 supplied. They are intended especially for class-room 

 demonstrations and use on such occasions as this meeting. 

 They are, however, convenient in the drug store. An in- 

 strument of this kind is very convenient for those phar- 

 macists who care to show physicians and other customers 

 some of the microscopical work they are doing. These 

 simple microscopes range in value from ten to seventy- 

 live cents. 



Before beginning the demonstration I will anticipate 

 one question. A simple microscope is not necessarily con- 

 fined to one lens, nor is it always simple in structure. It 

 may have one or more lenses and quite a complicated 

 mechanism for the purpose of bringing the lenses, object, 

 and light into a proper relationship with each other. A 

 simple microscope is one through which we see an enlarged 

 and erect image of an object. As an example you see the 

 letters right side up when you look at print through one 

 of these simple microscopes, or "magnifiers," or "magni- 

 fying glasses," as they are often called. 



The compound microscope also enables us' to see an en- 

 larged image of an object, but the image is inverted. I 

 will pass around this compound microscope with a speci- 

 men of lobelia seed mounted in glycerine. As you rotate 

 the microscope the seeds fall downward. This you can ob- 

 serve by watching the specimen with the naked eye. When 

 you look at the seeds through the microscope they seem 

 to run uphill. This appearance is due to the fact that the 

 image is inverted. 



The simple microscope is usually of low power and held 

 in the hand. The compound microscope is generally of 

 high power and provided with a stand. Some simple mi- 

 croscopes, however, are of quite high power, and we can 

 use very low powers with compound microscopes. 



