BOYLE'S PHILOSOPHY. 417 



It is singular how the mechanical theory or, as we now 

 term it, the dynamical theory, as applied to heat im- 

 pressed itself upon the philosophers of the seventeenth 

 century. Bacon defines heat as u a motion acting in its 

 strife upon the smaller particles of bodies." Boyle saw 

 clearly that when heat is generated by mechanical means, 

 new heat is called into existence, and believed that the 

 production of heat and electricity were somehow corre- 

 lated. Locke, in his Essay on the Human Understanding, 

 says that "what in our sensation is heat, in the object is 

 nothing but motion." Hooke plainly perceived heat as a 

 vibration, and denies the existence of anything without 

 motion, and hence perfectly cold. Yet it was the Material, 

 and not the Mechanical Theory, which prevailed and 

 which held the beliefs of the world up to our own time. 



When Boyle turns to the study of magnetism, his 

 lypothesis grows obscure. He denies, in the beginning, 

 Albert's conception that magnetic qualities flow from the 

 substantial Form of the lodestone, and, on the basis of ex- 

 periments showing the reversal of the poles and the de- 

 struction of magnetism by heat, he concludes that changes 

 in the " pores, or some other mechanical alterations or in- 

 ward disposition, either of the excited iron or of the lode- 

 stone itself," renders it capable or incapable of acting 

 magnetically. * 



His subsequent experiments, such as cooling and ham- 

 mering iron rods held north and south, are all old, and 

 are interesting simply as leading him to the more definite 

 dictum that "the change in magnetism communicated to 

 iron may be produced in good part by mechanical opera- 

 tions procuring some change in the texture in the iron." 1 



He is not in nearly so much doubt, however, concerning 

 the mechanical production of electricity. 2 Here he has 



1 Boyle : Experiments and Notes about the Mechanical Production of 

 Magnetism. London, 1676. 



2 Boyle : Experiments and Notes about the Mechanical Origine or Pro- 

 duction of Electricity. London, 1675. 



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