ME. MACQIJOEN EANKINE ON THE STABILITY OP LOOSE EARTH. 
27 
Let the siuLace of the earth be horizontal, and let the horizontal pressure have the 
least amount consistent with stability. Then 
and 
^ dx 1 + sin {p 
4tan^ „ 4sinip 
(73.) 
(74.) 
The last expression shows the ratio borne to the superincumbent load, by the upward 
tension necessary to extract from the earth a body with a nearly horizontal upper surface, 
like the thread of a screw pile. When the angle of repose, for example, is 30°, that 
. . 8 
ratio IS g. ■ 
§ 22. Resistance of Earth to the Horizontal Thrust of a Building. 
The hmit of the resistance of a horizontal stratum of earth to the horizontal thrust of 
the foundation of a building, is the upper limit of the horizontal thrust of the stratum, 
consistent with its w'eight ; that is to say, — 
