208 O. C. JONES, GEORGE D. HUBBARD Vol. XXII, No. 7 



tending of physical movements to carry beyond adjustment 

 through inertia. 



Continental masses and ocean basins have been demonstrated 

 through isostatic measurements to be in isostatic compensa- 

 tion. This means that the continents and basins must be due 

 to differential density, and that in this large configuration the 

 shape of the crust is still in accordance with our thesis. Earth- 

 quake studies have thrown light on this problem also.^^ 



CONCLUSION. 



We have seen that the phenomena of mountain-making, 

 volcanism, faulting, and earthquakes, together with density 

 differentiations, are due to the processes of adjustment, through 

 gravity of varying mass, to the equilibrium figure of the earth, 

 and that continental creep and sedimentary loading, especially 

 in deltas, though not due to this cause, yet are kept in isostatic 

 adjustment. Our conclusion is therefore as follows: the dynamics 

 of the lithosphere are essentially the processes of adjustment 

 of strains and stresses in the varied structures and materials of 

 the earth, adjustments to the equilibrium form of the earth, 

 through the force of gravity, involving diastrophism, volcanism, 

 and gradation. 



3<01dham, R. D., Q. J. G. S. London, Vol. 63, 1907, pp. 344-350. 



