Chapter IV: Matter and Ether

Inquiry regarding structure and material of the universe, 117 129

_Various hypotheses regarding matter_—
(1.) Greek notion of the _Atom_, 118 130
Speculations of Lucretius, 119-130 131
(2.) Theory of Boscovich (centres of force), 131 137
(3.) Theory of infinite divisibility, 132 138
(4.) Vortex-atom theory, 133-134 139
Remarks on these theories, 135-136 141

Relative quantity of matter associated with energy, 137-138 142

_Universal gravitation_—
Is a weak force, 139 144
Two ways of accounting for it, 140 145
Le Sage’s hypothesis, 141-142 146

_The Ethereal medium_—
Its principal properties apparently incongruous, 143 148
Analogy of Professor Stokes, 144 149
Distortion and displacement of ether, 145 149
Inferior limit of its density, 146 150
Its supposed imperfect transparency, 147 151
Remarks on ether, 148 153

Remarks on the speculations of this chapter, 149-150 154

Modification of the vortex-ring hypothesis, 151-152 155

Possible disappearance of the visible universe, 153 157