566 



GEOLOGY. 



horizons to higher ones and to the surface, and that this still continues 

 at a diminished rate. It assumes that whenever the interior heat raised 

 any constituent of the interior matter above its fusing-point under the 



Pressures in 



Million 



Megadynes, 



3.1 



3.0 

 2.9 

 2.7 

 2.5 

 2.3 

 2.0 

 1.8 

 1.5 

 1.2 

 0.9 

 0.7 

 0.5 

 0.3 

 0.2 

 0.1 



Center 



l^ 



^ 













































\ 











































N 



\, 









































s 



\, 









































s 



X^o 

































^^ 



-^ 



^ 





' 



\, 































-^ 







\ 



-^ 



s 



\, 

































^^ 



\ 







<s 



s 



































\ 



\, 





\ 



\^ 



\, 



































\ 





\ 







^ 

































X 



N 



\ 



S^ 



\ 



s^ 

































S 



^ 



\ 



N 





^ 



^ 

































\ 



\ 



N 







\^ 



N 































V 



\ 

 N 











































X\ 









































\. 



^ 



^ 



Temperatures in 



Degrees C. 



32000 



30000 



28000 



26000 



24000 



22000 



20000 



18000 



16000 



14000 



12000 



10000 



8000 



6000 



4000 



2000 



0000 



1.0 

 Surface 



Fig. 452. — Diagram illustrating the distribution of temperature under the accretion 

 hypothesis (neglecting the heat from inf all and other external sources). The divi- 

 sions of the base-line represent fractions of the earth's radius. The vertical divisions 

 represent both pressure in megadynes per sq. cm., nearly the same as atmospheres 

 per sq. in., at the left, and temperatures in degrees C. at the right. It is to be noted 

 that the temperature scale is 2000° C. per division, while that of Fig. 451 is 5000° C. 

 per division. The upper curve at the left, PC, is the pressure curve. The middle 

 curve, DC, is the density curve, beginning at 2.8 at the surface and reaching nearly 

 11 at the center. The lower curve, TC, is the temperature curve, rising from the surface 

 temperature, 0° C, at the right, to 20,000° C. at the center. It is to be noted that 

 the portion of this curve at the left representing the deeper part of the earth is con- 

 vex upwards, while the portion at the right is concave. It will be seen that the 

 gradient increases from the center to a point between ,6 and .7 radius, and then 

 decreases, and that between ,8 radius and the surface, a distance of about 800 miles, 

 the decrease is notable. This means that with an equal coefficient of conductivity 

 the flow from the center outward to .6 or .7 radius will be faster than the flow from 

 .8 radius to the surface, neglecting the immediate surface effects of external cooling. 

 These curves were worked out by Mr. Lunn. 



local pressure, it passed into the liqmd state, and was forced outwards hy 

 the stress differences to which it was subjected, unless its specific gravity 

 was sufficiently high to counterbalance them. It is conceived that the 

 more fusible portions were liquefied first, and that in so doing they 



