Properties of Matter and Ether compared--Discontinuity _versus_ Continuity--Size of atoms--Astronomical distances--Number of atoms in the universe--Ether unlimited--Kinds of Matter, permanent qualities of--Atomic structure; vortex-rings, their properties--Ether structureless--Matter gravitative, Ether not--Friction in Matter, Ether frictionless--Chemical properties--Energy in Matter and in Ether--Matter as a transformer of Energy--Elasticity--Vibratory rates and waves--Density--Heat--Indestructibility of Matter--Inertia in Matter and in Ether--Matter not inert--Magnetism and Ether waves--States of Matter--Cohesion and chemism affected by temperature--Shearing stress in Solids and in Ether--Ether pressure--Sensation dependent upon Matter--Nervous system not affected by Ether states--Other stresses in Ether--Transformations of Motion--Terminology p. 24 CHAPTER III Antecedents of Electricity--Nature of what is transformed--Series of transformations for the production of light--Positive and negative Electricity--Positive and negative twists--Rotations about a wire--Rotation of an arc--Ether a non-conductor--Electro-magnetic waves--Induction and inductive action--Ether stress and atomic position--Nature of an electric current--Electricity a condition, not an entity p. 94 CHAPTER I Ideas of phenomena ancient and modern, metaphysical and mechanical--Imponderables--Forces, invented and discarded--Explanations--Energy, its factors, Kinetic and Potential--Motions, kinds and transformations of--Mechanical, molecular, and atomic--Invention of Ethers, Faraday's conceptions. 'And now we might add something concerning a most subtle spirit which pervades and lies hid in all gross bodies, by the force and action of which spirit the particles of bodies attract each other at near distances, and cohere if contiguous, and electric bodies operate at greater distances, as well repelling as attracting neighbouring corpuscles, and light is emitted, reflected, inflected, and heats bodies, and all sensation is excited, and members of animal bodies move at the command of the will.'--NEWTON, _Principia_.