CHAPTER VIII.

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