NOTE VI … CENTRAL FIRES.
Sun's heat much less than that from the fire at the earth's centre; sun's heat penetrates but a few feet in summer; some mines are warm; warm springs owing to subterraneous fire; situations of volcanos on high mountains; original nucleus of the earth; deep vallies of the ocean; distant perception of earthquakes; great attraction of mountains; variation of the compass; countenance the existence of a cavity or fluid lava within the earth.