226 



TOWERS AND TANKS FOR WATER-WORKS. 



aging .5 cu. ft. per foot length. Although continuing to 

 penetrate under the blows of the hammer considerably more 

 than in., the piling was stopped at 60 ft., upon the theory 

 that the frictional resistance through that depth would equal 

 .'5 ton per foot of pile length or 3000 tons for the 100 piles. 

 Assuming a factor of safety of 5, the safe bearing was deter- 

 mined at 600 tons, which represented the total weight of the 

 tank, water, wind-stresses, and foundations. 



No observable settlement in this foundation has taken 

 place in several years. The piles were sawn and capped ; the 

 longitudinal spaces were filled with concrete flush to the top 

 of stringers, and the grillage floored, all timber being below 

 the point of saturation of the soil. All earth foundations 

 must yield somewhat, but this is not important in the case 

 of isolated structures such as stand-pipes and the like, pro- 

 vided the settlement is gradual and uniform, and not of radical 

 extent. 



The following table represents the safe values of ordinary 

 soils according to Prof. Ira O. Baker: 



SAFE BEARING-VALUE OF SOILS. 



Stone Masonry. The requirements for a serviceable 

 foundation building stone are, in the main, that it shall be 



