State of Earth’s Interior. 19 
clusion is a nonsequitur, because he fails to recognize the changed 
conditions. As the line descends, pressure increases directly as the 
line lengthens. Now, one class of physicists claim that the incre- 
ment of pressure is persistently superior to the increment of heat 
but these physicists fail to notice that, when high temperature and 
high pressure are simultaneously exerted on the same rock, the 
character of the rock is changed, so that it becomes a far higher 
conductor of heat; and that, therefore, the incremental ratio for the 
heat very far exceeds the increment of pressure. Hence fluidity is 
assured ; but, this point once reached, another law comes in, viz. : 
The conduction and interstitial radiation become extremely rapid 
through the fluid mass, so that the temperature of the fluid is uniform 
with the temperature of the entire nucleus, and therefore no further 
augmentation can take place; but the ratio of pressure augmentation 
does not change. So that the increasing pressure soon overtakes 
the expanding power of the maximum heat, passes its limits, and 
solidifies all the nucleus within this limit. 
An ideal section through the Earth’s centre will, therefore, show 
the following : 
First, an outer solid envelope. 
Second, a semifluid envelope. 
Third, a fluid envelope. 
Fourth, a semifiuid envelope. 
Fifth, a solid nucleus, : 
No. 1 results from reduced temperature alone. 
No. 2 results from pressure and a temperature not quite suffi- 
cient for liquefaction. 
No. 3 results from a temperature sufficiently high to liquefy it 
under high pressure, and is the maximum temperature. 
No. 4 results from the increase of pressure so as to be just 
overtaking the expansive power of the maximum temperature. 
No. 5 results from a pressure so high as to overcome, completely, 
the expansive power of Earth’s maximum heat. 
At the centre of Earth the pressure, taking her general average, 
5%, water being unity, is 7,180,593,750 lbs. to the square foot—a 
pressure so enormous that no known substance could fuse beneath 
it at Earth’s maximum temperature. Even hydrogen would be as 
hard as diamond at this maximum temperature of the internal 
nucleus. 
