58 ESSEX WORTHIES. 



south. Most of these experiments were original with Gilbert, and are 

 indicated as such by him, by the placing of an asterisk opposite the 

 account of them in the margin of the book. These experiments and 

 aphorisms are continued in Chapter xxxiii., which deals mainly with 

 the swiftness of the magnetic motions, and he states that the speed of 

 the motion is proportional (inversely) to the distance. He also 

 showed that the magnetic forces between two distant magnets could 

 be conducted from one to the other by interposing a rod of iron ; the 

 magnetic virtue being transmitted through iron much better than 

 through air. At the end of this chapter he describes the method of 

 obtaining magnetic figures by sprinkling iron filings upon a card laid 

 over a magnet ; and remarks on the movements of the tufts of filings 

 when the magnet beneath is moved. Chapter xxxv. contains a most 

 characteristic diatribe against certain earlier authors, Cardan, Peter 

 Peregrinus and John Taysnier, who had pretended that a perpetual 

 motion machine might be made by means of a magnet ; and ends by 

 exclaiming : Would that the gods might send to perdition all such 

 false, misleading and crooked labours by which the minds of studious 

 men are warped ! 



Book III. is mainly occupied with the directive action of the 

 compass and of loadstones, and of the property of polarity — or 

 vcrticity — in general. Chapter i. describes further experiments with 

 the terrella made to illustrate observations made on the compass in 

 distant lands which had been communicated to Gilbert by Francis 

 Drake — experiments which fully confirmed his theories, and the 

 results of which are summed up by saying that all magnetic bodies 

 behave toward the globe of the earth precisely as other magnets 

 behave toward the terrella, the laws of their action being alike. In 

 the following chapters further experiments with loadstones and 

 needles are described, relating chiefiy to the results of touching one 

 with the other. Amongst other matters which helped him to this 

 conclusion was his discovery that if a rod of iron is hammered whilst 

 lying in a north-and-south position it becomes magnetized by the 

 influence of the earth's magnetism. This observation is illustrated 

 by a quaint woodcut, which is reproduced on a smaller scale in 

 Fig. 3- 



Books IV. and V. go into some geographical and astronomical 

 matters ; being intended chiefly as a contribution to the nautical 

 api)lications of his studies. He describes sundry instruments, one 

 of them, for ascertaining the variation of the compass in different 



