84 



sun's rays. According to the theory that the centre of the earth 

 is hot, and that you increase your warmth as you approach that 

 centre, this depth of 7 miles should reach a heat more than suffi- 

 cient to melt lead. No doubt from the mobility of water it would 

 convey away and lose this heat to a great extent ; but it is a bad 

 conductor of heat, and therefore it would only convey it away, 

 not allow it to radiate away, and consequently we ought to find 

 that the water was still being heated from below, whereas it 

 never seems to have been so heated — for if in a time past the 

 cause of the higher temperature was central heat, we find a 

 previous era existed when the waters were evidently icy cold, 

 instead of being always as they should have been cooling slower 

 than the earth. 



But lastly, if it be granted that the heat increases in the pro- 

 portion to .descent, then, as I before mentioned, the interior of 

 the earth must be in a molten state, and the solid crust must be 

 a mere shell of not more than 100 miles thick or one eightieth of 

 the diameter of the earth. Now it is a well ascertained fact that 

 our globe in its diurnal revolution, spins upon an axis Avhich does 

 not always point to the same spot in the heavens, but like a top 

 slowly works its axis round in a circle. Now the caiise of this 

 motion which causes the precession of the equinoxes may be 

 shortly explained thus : — If a ring of satellites be supposed to 

 revolve in the plane of the equator round the earth, at the 

 summer solstice, when the north axis of the earth is inclined 

 towards the sun, this ring of satellites would, on the side nearest 

 to the sun, where its attraction was gi-eatest, be below the plane 

 of the earth's annual orbit, consequently the sun's attraction 

 would tend to alter this, and incline them upward as they came 

 on the side nearest to the sun, and if this ring of satellites be 

 supposed to be a rigid ring in contact with, and adhering to this 

 earth, it would tend to bend the axis of revolution upwards, or 

 at right angles to the path of annual revolution. Of course the 

 reverse motion would be produced at the winter solstice, this 



