MAGNETIC FIELDS 



177 



Just as you 

 made blue 

 prints of leaves 

 and small ob- 

 jects, and cop- 

 i e d drawings, 

 so you can ob- 

 tain blue prints 

 o f magnetic 

 fields. The il- 

 lustration gives 

 one example of 

 a magnetic field. You can make many. 



Experiment 75. Blue Prints of Magnetic Fields. 



Apparatus: Two bar magnets, piece of window 

 glass, iron filings in a salt shaker. 



Materials: Blue-print paper. 



a. Lay the two magnets upon a book, side by side, 

 about the width of the magnets apart, having the two 

 north poles pointing in the same direction. Lay a piece 

 of blue-print paper upon the magnets with the yellow side 

 up. Keeping in the shade, sprinkle iron filings upon the 

 paper as in the last experiment. When the filings are 

 nicely arranged cover them carefully with the piece of 

 window glass, and place in the bright sunlight. When 

 the paper has changed to the familiar bronze, return the 

 filings to the shaker and immediately wash the blue print 

 in water. 



b. Repeat (a) above, but have the north pole of one 

 magnet and the south pole of the other magnet pointing 

 the same way. After the blue-print is made compare it 



Elem. Sci. 12 



