EARTH S INTERIOR ADAMS AND WILLIAMSON 



259 



PRESSURE IN THE EARTH 



The pressures corresponding to the present density distribution 

 were obtained by graphical integration 85 from the densities shown 

 by the full line in Figure 3. A graph of the pressure at various 

 depths within the earth is shown in Figure 6. At the center the 

 pressure is 3.18 millions of megabars (practically 3 million atmos- 

 pheres) , and is remarkably close to the value 3.08 million megabars, 

 obtained from Laplace's equation with a surface density 2.7. 



£ft>6 32.DO 4 000 



£>ep?S> "7 /f,/omet<=r 



Fig. 6. — Pressure as a function of depth, derived from the full line curve of Figure 3. 

 A niegabar is about one atmosphere. More exactly. 1 megabar=0.987 atm. 



CONCLUDING REMARKS 



In conclusion we refer to the following passage from the Annual 

 Eeport of the Director of the Geophysical Laboratory : 36 



Both science and story have left the interior of the earth virtually a closed 

 book. Imaginative writers have forecast many of the conquests of the sea 

 and of the air and of the regions beyond, but the interior of the earth remains 

 inaccessible to them; scientific effort has often been consciously and even 

 eagerly directed toward it, but has revealed scarcely more. The distance 



85 The equation is : 



•/ 



6.66X10-»TOp 



dr 



in which m is obtained by another graphical integration of the equation: 



r 

 771=4x1 pr'tfr 



30 Dr. Arthur L. Day, director. The report appears in the Year Book of the Carnegie 

 Institution of Washington, No. 22 (1923). 



