A HISTORY OF SCIENCE 



first, to begin with the common stony and ferruginous 

 matter, and magnetic bodies, and the part of the earth 

 that we may handle and may perceive with senses, 

 and then to proceed with plain magnetic experiments, 

 and to penetrate to the inner parts of the earth." 5 



Before taking up the demonstration that the earth 

 is simply a giant loadstone, Gilbert demonstrated in 

 an ingenious way that every loadstone, of whatever 

 size, has definite and fixed poles. He did this by 

 placing the stone in a metal lathe and converting it 

 into a sphere, and upon this sphere demonstrated how 

 the poles can be found. To this round loadstone he 

 gave the name of terrella that is, little earth. 



"To find, then, poles answering to the earth," he 

 say a, "take in your hand the round stone, and lay on 

 it a needle or a piece of iron wire : the ends of the wire 

 move round their middle point, and suddenly come to 

 a standstill. Now, with ochre or with chalk, mark 

 where the wire lies still and sticks. Then move the 

 middle or centre of the wire to another spot, and so to 

 a third and fourth, always marking the stone along 

 the length of the wire where it stands still ; the lines so 

 marked will exhibit meridian circles, or circles like 

 meridians, on the stone or terrella ; and manifestly they 

 will all come together at the poles of the stone. The 

 circle being continued in this way, the poles appear, 

 both the north and the south, and betwixt these, mid- 

 way, we may draw a large circle for an equator, as is 

 done by the astronomer in the heavens and on his 

 spheres, and by the geographer on the terrestrial 

 globe." 8 



Gilbert had tried the familiar experiment of placing 



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