384 FRAGMENTS OF SCIENCE 



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 generalization. We soon recognize a brother- 

 hood between the larger phenomena of Nature and the 

 minute effects which we have observed in our private 

 chambers. Why, we inquire, does the magnetic needle 

 set north and south? Evidently 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 "dipping" its 

 point, or its eye, below 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 toward 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 ex- 

 actly vertical. Move it back to the centre, it resumes its 

 horizontality; pass it on toward the south pole, its north 

 end now dips, and directly over the south pole the needle 

 becomes vertical, its north end being now turned down- 

 ward. Thus we learn that on the one side of the mag- 

 netic 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 



