738 



JOSEPH BARMELL 



indefinitely extended elastic solid. The amount and direction of 

 the vertical stress upon this plane are shown by the vertical lines, 

 the scale of stresses being one-twentieth of the value for the stress- 

 diagram shown by the horizontal lines. On this plane, S-S, a 

 small unit mass is subjected to stress equal in all directions and 

 not to stress-difference, since the stress is essentially the same on 

 the small contiguous unit masses. The reasoning is the same as 



Fig. 17. — Stress-diagrams for harmonic loads distributed on a plane: A, diagram 

 for loads upon a limiting surface of a solid extending indeiinitely from this surface. 

 B, diagram for loads upon a plane within an indefinitely extended solid. The scale 

 for loads is one-twentieth of the scale for the resulting stresses. A little more than 

 one-half wave-length is shown. 



that for harmonic loads distributed on the limiting surface of a solid 

 except that here there is an indefinitely extended solid on each side 

 of the plane. The stress at any point of the plane acts positively 

 on one side, negatively on the other. Half of the load will be 

 carried on each side. Consequently if OA is the curve showing 

 the stress-differences at various depths for a harmonic load on the 

 surface of the earth, then BOB will be the stress-curve for the same 

 load carried on a plane deep within the lithosphere. For this to 

 be approximately true, however, the wave-length would have to be 



