THE MOST CURIOUS CRAFT AFLOAT 



225 



VIEW OF THE NON-MAGNETIC YACHT CARNEGIE AT EALMOUTH, ENGLAND 



back and forth just as did the magnetic 

 needle, and, when it comes to rest, it again 

 hangs vertical. The force which was in 

 operation during this experiment was 

 precisely the same as that acting on the 

 falling apple. Is this also the force 

 which acted on the swinging compass 

 needle? No, because the latter was mov- 

 ing to and fro in a horizontal plane, and 

 gravity only acts in a vertical direction. 



THE MAGNETIC DIP NEEDLE 



Suppose we were to take now a "dip 

 needle," such as was used for the first 

 time by an ingenious and painstaking 

 English instrument maker, Robert Nor- 

 man, in 1576. This needle is so mounted 

 that, instead of being able to swing in 

 a level plane, it swings in a vertical one. 

 Nomian discovered that no matter how 

 carefully he had balanced the needle be- 

 fore it was magnetized, after touching 

 it with the lodestone, so as to magnetize 

 the needle, then there was no longer a 



perfect balance, but "that presently the 

 north point thereof would bend or de- 

 cline downwards under the horizon in 

 some quantity." He at first thought that, 

 in spite of his care, he had overweighted 

 the end that dipped below ; however, 

 upon repetition of the experiment, he 

 invariably found the same result, and 

 thus was discovered the so-called "dip 

 of the magnetic needle." If the two 

 ends of the magnetized needle are pre- 

 cisely equal in weight, and still the needle 

 won't remain level after magnetizing, 

 then evidently we must have some other 

 force acting than gravity. And the mys- 

 tery increases, for, if we use a brass 

 needle instead of a steel one, no matter 

 how much we stroke it with the "mag- 

 netizing irons," it persists in remaining 

 level. 



Evidently we are dealing with a force 

 difi^erent from that acting on a falling 

 body. While gravity affects all sub- 

 stances alike, magnetism, affects but a 



