SCIENTIFIC METHOD 75 



then may be called a terrella, or earthkin. Place on it 

 a piece of iron wire. The ends of the wire move round 

 its middle point and suddenly come to a standstill. 

 Mark with chalk the line along which the wire lies 

 still and sticks. Then move the wire to other spots 

 on the terrella and repeat your procedure. The lines 

 thus marked, if produced, will form meridians, all 

 coming together at the poles. Again, place the mag- 

 net in a wooden vessel, and then set the vessel afloat 

 in a tub or cistern of still water. The north pole of the 

 stone will seek approximately the direction of the 

 south pole of the earth, etc. It was on the basis of 

 scores of experiments of this sort, carried on from 

 about 1582 till 1600, that Gilbert felt justified in 

 concluding that the terrestrial globe is a magnet. 

 This theory has since that time been abundantly 

 confirmed by navigators. The full title of his book 

 is Concerning the Magnet and Magnetic Bodies, 

 and concerning the Great Magnet the Earth: A 

 New Natural History {Physiologia) demonstrated 

 by many Arguments and Experiments. It does not 

 detract from the credit of Gilbert's result to state 

 that his initial purpose was not to discover the nature 

 of magnetism or electricity, but to determine the true 

 substance of the earth, the innermost constitution of 



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the globe. He was fully conscious of his own method 

 and speaks with scorn of certain writers who, having 

 made no magnetical experiments, constructed ratio- 

 cinations on the basis of mere opinions and old- 

 womanishly dreamed the things that were not. 



Galileo (1564-1642) even as a child displayed 

 something of the inventor's ingenuity, and when he 

 was nineteen, shortly after the beginning of Gilbert's 



