276 INTRODUCTION TO GENERAL SCIENCE 



Materials: Sheet of bristol board, 22" X 28". 



a. To make a megaphone: Tie a string two feet long to a 

 pencil, and with a radius of twenty-two inches, using one 

 corner of the bristol board as a center, draw as long an arc as 

 possible on the paper. With the same point as a center, and 

 with a radius of four inches, describe another arc. Cut the 

 bristol board along the lines. Now roll up the bristol board 

 to form a funnel, and fasten every five or six inches, along 

 the edge, with the paper rivets. 



6. Send your partner a hundred feet away, and speak to him 

 in an ordinary tone of voice. He will probably not hear you. 

 Now place the small end of your megaphone to your lips, 

 direct the large end toward your partner, and speak to him 

 in the same tone of voice. Does he hear you? Have your 

 partner speak to you in the same manner. Go so far away 

 from your partner that you can just carry on a conversation 

 by means of the megaphone. Does the megaphone help? 

 The megaphone prevents the vibrations of the voice from 

 spreading, and guides them in the desired direction. 



c. Punch a hole in the center of the bottom of the cans, 

 with a nail. Push a string through the hole in each, and tie 

 a knot in it to keep it from slipping through again. The 

 cans should be separated by a string at least one hundred 

 feet long. Hold the can to your mouth and have your partner 

 hold his can to his ear. Try whispering to him. Have him 

 repeat your actions. The string must be held taut, for it 

 carries the vibrations, and the more characteristics of a solid 

 which it has, the better will the vibrations be carried. 



A telephone like this may be used for a distance of one 

 mile. Very satisfactory results may be obtained by the fol- 

 lowing method: At each end of the line a board, one foot 

 wide, should be fitted in a window. In the board should be 



