364 FRAGMENTS OF SCIENCE. 



In this thorough manner we must master our ma- 

 terials, reason upon them, and, by determined study, 

 attain to clearness of conception. Facts thus dealt 

 with exercise an expansive force upon the intellect ; 

 they widen the mind to generalisation. We soon 

 recognise a brotherhood between the larger phenomena 

 of Nature and the minute effects which we have ob- 

 served in our private chambers. Why, we enquire, 

 does the magnetic needle set north and south ? Evi- 



O 



dently it is compelled to do so by the earth ; the great 

 globe which we inherit is itself a magnet. Let us 

 learn a little more about it. By means of a bit of 

 wax, or otherwise, attach the end of your silk fibre to 

 the middle point of your magnetic needle ; the needle 

 will thus be uninterfered with by the paper loop, and 

 will enjoy to some extent a power of f dipping' its 

 point, or its eye, belpw the horizon. Lay your bar 

 magnet on a table, and hold the needle over the equator 

 of the magnet. The needle sets horizontal. Move it 

 towards the north end of the magnet ; the south end 

 of the needle dips, the dip augmenting as you approach 

 the north pole, over which the needle, if free to move, 

 will set itself exactly vertical. Move it back to the 

 centre, it resumes its horizontality ; pass it on towards 

 the south pole, its north end now dips, and directly 

 over the south pole the needle becomes vertical, its 

 north end being now turned downwards. Thus we 

 learn that on the one side of the magnetic equator the 

 north end of the needle dips; on the other side the 

 south end dips, the dip varying from nothing to 90. 

 If we go to the equatorial regions of the earth with a 

 suitably suspended needle we shall find there the 

 position of the needle horizontal. If we sail north one 

 end of the needle dips ; if we sail south the opposite 

 end dips; and over the north or south terrestrial 



