1895 THE MICROSCOPE- 7 



The flies are great scavengers, feeding on all kinds of 

 decaying matter and noxious gases, detecting them even 

 before we do. In this way they are a great benefit. Not- 

 ice the hairs on the legs, feet and tongue, take one of last 

 year's flies, see the particles of dust clinging to the hair. 

 Now will not the particles from the decaying substances 

 upon which it feeds and bacilli of diseases cling to 

 them in the same way ? It is in this way that he caries 

 contageous diseases and he should be kept away from 

 our food. When the fly is seen rubbing his legs togeth- 

 er he is r.sing the little hairs of the tarsi to cleau him- 

 self from these particles. 



If the microscope is used in the evening, you may find 

 that the object does not show distinctly. This is be- 

 cause it is not properly lighted. It is best to use a 

 small coal-oil lamp, having it six or eight inches from the 

 mirror and shading the light from the eyes by a piece of 

 paper hung to the lamp chimney by a bent hair pin and 

 of such length as to allow the light to fall strongly on an 

 object. This with the mirror turned so as to show a white 

 field will give a good outline or show a transparent ob- 

 ject well, but it is not sufiicient for opaqae objects. 

 We need a condenser — something to throw^ a strong light 

 on the object only. This, can be made at home by get- 

 ting at the opticians a double convex lens about the size 

 of a coat button and cutting a piece of sole leather in the 

 shape shown in Fig. 2, having a round opening in the 

 center. With a sharp knife, divide the leather at the 

 round end and around the opening so as to make a case 

 for the lens. In the small end insert a wire about four 

 inches long bent at the other end as shown in the dia- 

 gram and insert this bent end in the center of a spool. 



Place this between the lamp and the mirror and by 

 moving it or changing the height by moving the wire 

 up or down in the spool throw the point of light directly 

 on the object to be seen. The dark background must 



