196 



EXPERIMENTAL GENERAL SCIENCE 



tween the true north pole and the one toward which the needle 

 points. A magnetized needle mounted to swing in a perpen- 

 dicular circle is called a dip-needle. 

 When a dip-needle is carried toward 

 the north magnetic pole, its north 

 pole begins to dip downward and, at 

 the pole, assumes a perpendicular 

 position. The magnetic pole may 

 therefore be located either by the 

 dip-needle or the compass. 



162. Lines of Force. If a piece of 

 paper be laid over a magnet and iron 



filings sprinkled upon it, a gentle tapping of the paper will 

 cause the filings to arrange themselves in curious patterns, 

 which indicate the lines of force proceeding from the magnet. 



FIG. 69. Iron filings showing lines of force about a bar magnet. (Tower, 

 Smith and Turton.) 



It will be seen that these lines tend to circle around from one 

 pole to the other. The arrangement of the filings is due to 

 the fact that each particle is for the time a magnet, and takes 



