278 FRAGMENTS OF SCIENCE. 
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 fiber to the middle 
point of your magnetic needle; the needle will thus be un- 
interfered 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 aug- 
menting as you approach the north pole, over which the 
needle, if free to move, will set itself exactly vertical. 
Move it back to the center, 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 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 we go 
to the equatorial regions of the earth with a suitably sus- 
pended 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 magnetic pole the needle sets vertical. The 
south magnetic pole has not yet been found, but Sir James 
Ross discovered the north magnetic pole on June 1, 1831. 
In this manner we establish a complete parallelism between 
the action of the earth and that of an ordinary magnet. 
The terrestrial magnetic poles do not coincide with the 
geographical ones; nor does the earth's magnetic equator 
quite coincide with the geographical equator. The direc- 
tion of the magnetic needle in London, which is called the 
magnetic meridian, encloses an angle of 24 degrees with 
the astronomical meridian, this angle being called the 
Declination of the needle for London. The north pole of 
the needle now lies to the west of the true meridian; the 
declination is westerly. In the year 1660, however, the 
declination was nothing, while before that time it was 
easterly. All this proves that the earth's magnetic con- 
stituents are gradually changing their distribution. This 
