MAGNETISM 159 



Stanford University the compass points 19 degrees east of the true 

 north. (1899.) 



A pretty experiment to show lines of magnetic force can be 

 performed by shaking a few fine iron-filings over a piece of paper 

 or glass under which the magnet is placed. If the lines do not 

 form at once, shake the paper or glass gently. 

 i The children may be interested in finding out about natural 

 magnets, how magnets are made, and their uses. 



Variation of the Magnetic Needle. 



To determine the true direction of the magnetic needle (that 

 is, the "variation of the needle"): After dark on a clear night 

 suspend two plumb lines (threads with weights attached about 

 one foot apart) from suitable supports. The back of a chair may 

 be used for this. Then bring the two stretched threads in an 

 exact line with the North Star. On a support (a box on end will 

 do) between the lines lay a sheet of paper horizontally placed. 

 With a ruler and pencil draw a line on the paper Justin line with 

 the two threads. This line, if all is done carefully, is approxi- 

 mately the true north and south direction. By placing the com- 

 pass on this line, the "variation" of the needle will be found to 

 be about 19 degrees east of north that is, the true north is 19 

 degrees west of the magnetic north. This varies in the different 

 parts of the world very much, and is changing, slightly, every 

 year here (Stanford University). 



It must also be remembered that the North Star has an 

 apparent daily revolution of a very small diameter about the true 

 north, consequently it is exactly north but twice in twenty-four 

 hours, but it requires more accurate instruments than ours 

 to detect these differences. (See text-books on Physical Geog- 

 raphy and Astronomy.) 



Many questions will rise in connection with this rather 

 simple experiment, which with some of the grades may be 



