370 FRAGMENTS ,OF SCIENCE. 



order, and to supply what is needed to render the explana 

 tion complete. Do not quit the subject until you thor 

 oughly understand it ; and if you are able to look with 

 your mind s eye at the play of forces around a magnet, and 

 see distinctly the operation of those forces in the produc 

 tion of the magnetic curves, the time which we have spent 

 together has not been spent in vain. 



In this thorough manner we must master our materials, 

 reason upon them, and, by determined study, attain to clear 

 ness of conception. Facts thus dealt with exercise an 

 expansive force upon the boundaries of thought ; they 

 widen the mind to generalization. We soon recognize a 

 brotherhood 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 your silk fibre to your 

 magnetic needle by a single point at its middle, 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 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 exactly vertical. 

 Move it back to the centre, it resumes its horizontal it y ; 

 pass it on toward the south pole, its north end now dips, 

 and directly over the south pole the needle becomes ver 

 tical, its north end being now turned downward. 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 ninety degrees. If 



