Inquiry into the Interior Construction of the Earth. What is really known of the exterior or surface 142 What is known of the interior 143 Little to be learned from Geology, which reaches very few miles down 144 Various notions of the interior 145 What is learnt from earthquake and volcanoes. Igno-aqueous fusion, liquid magma. 146 Generally believed that the earth consists of solid matter to the centre. Mean density. Surface density 147 More detailed estimate of densities near the surface 148 Causes of increased surface density after the crust was formed 148 Calculations of densities for 9 miles deep, and from there to the centre forming Table IV. 150 Reflections on the results of the calculations 151 Notion that the centre is composed of the heaviest metals. "Sorting-out" theory absurd 151 Considerations as to how solid matter got to the centre 152 Gravitation might carry it there, but attraction could not 153 How the earth could be made out of cosmic matter, meteorites or meteors 154 CHAPTER IX. Inquiry into the Interior Construction of the Earth--_continued_ 165 The earth gasiform at one period. Density including the moon may have been 1/10,000th that of air. Must have been a hollow body. Proofs given 166 Division of the mass of the earth alone into two parts 169 Division of the two masses at 817 miles from surface 171 Reasons why the earth cannot be solid to the centre 172 Gasiform matter condensing in a cone leaves apex empty 172 Proportions of the matter in a cone 173 Calculations of the densities of the outer half of the hollow shell of the earth. Remarks upon the condensation 174 Calculations of inner half of the hollow shell 175 Remarks upon position of inner surface of the shell 177 Calculations of the same 179 CHAPTER X.