' MAGNETISM 1 59 



Stanford University the compass points 19 degrees east of the true 

 north. (1899.) 



A prett}' 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 

 _vear 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 dilferences. (See text-books on Physical Geog- 

 raphy and Astronomy.) 



Manv questions will rise in connection with this rather 

 simple exjieriment, wliich with some of the grades may be 



