STORAGE AND DISTRIBUTION. 137 



forcing steel than can now be obtained, and whether 

 it is practicable to construct in reinforced concrete to 

 resist hydrostatic heads of 100 ft. to 300 ft., such as 

 is demanded for great dams and pressure conduits. 



One set of experiments with mixtures as lean as 

 i 14: 14, intended to secure the highest possible 

 degree of permeability to serve as drainage blocks 

 through which seepage of water might be carried 

 away, became so nearly impervious in twenty-four 

 hours under a head of 20 in. as to make doubtful 

 their use for the purpose intended. This was with 

 the flow perpendicular to the bed of the blocks. With 

 the blocks so placed that the flow was parallel to the 

 bed, the flow was greatly increased. 



The difficulties in securing perfect workmanship 

 in mixing and placing the concrete, and avoiding the 

 formation of bedding planes through the mass, are 

 greater than are those resulting from lack of know- 

 ledge of what should be done. 



For storing smaller quantities of water cast-iron 

 or steel tanks are used. For estate water supply 

 the cast-iron tank has much to recommend it, because 

 the sections are cast and machined in the works, 

 are small and comparatively light in weight, conse- 

 quently transport to the country is rendered easy, 

 while the fitting together does not demand skilled 

 labour. Steel tanks which find much favour in very 

 large sizes on important works are not at all well 

 adapted to this particular purpose, because much of 

 the work has to be done on the site and by skilled 

 labour. These remarks, however, do not apply to 

 very small galvanized steel tanks which find use in a 

 variety of places. Cast-iron tanks can be erected to 



