CONTENTS xi 



Voigt's theory connecting pyroelectricity and piezoelectricity Electric 

 deformation of crystals Lippmann's theory Verification by the Curies 

 Dielectric subjected to uniform pressure Change of temperature of a pyro- 

 electric crystal on changing the potential Pp. 148-163 



PART II: MAGNETISM 



CHAPTER XIII 



GENERAL ACCOUNT OF MAGNETIC 

 ACTIONS 



Natural and artificial magnets Poles Mechanical action of poles on each other 

 The two poles have opposite mechanical actions In a well-magnetised bar 

 the poles are near the ends The two poles always accompany each other in 

 a magnet The two poles are equal in strength The magnetic action takes 

 place equally well through most media Induced magnetisation Magnetisa- 

 tion can take place without contact Retentivity and permanent magnetism 

 The earth is a great magnet Magnetisation induced by the earth 

 Methods of magnetisation Single touch Divided touch Double touch 

 The electro-magnetic method Electro-magnets Ball-ended magnets 

 Horseshoe magnets Compound magnets Distribution of magnetisation 

 Consequent poles Magnetisation chiefly near the surface Saturation and 

 supersaturation Preservation of magnetisation Armatures Portative force 

 Nickel and cobalt magnets The magnetic field Lines of force mapped 

 by iron filings Pp, 165-180 



CHAPTER XIV 



GENERAL ACCOUNT OF MAGNETIC 

 ACTIONS continued 



Relation between magnetisation and the magnetising force producing it The 

 hysteresis loop^ Susceptibility and permeability Magnetisation and tem- 

 perature Permeability and temperature Change of length on magnetisation 

 Magnetisation and strain Pp. 181-191 



CHAPTER XV 



MOLECULAR HYPOTHESIS OF THE 

 CONSTITUTION OF MAGNETS 



Molecular hypothesis Ewing's theory and model Dissipation of energy in a 

 hysteresis cycle Temperature and magnetisation Attempts to explain the 

 constitution of molecular magnets Pp. 192-202 



