232 TOWERS AND TANKS. FOR WATER-WORKS. 



was concentrated upon the 12 X i8-in. washer used as a cap r 

 and this downward tendency was resisted by the holding-down 

 power of three 12 X 12-111. washers in the three other piers, 

 or a total of 648 square inches. Investigations made after 

 the failure show that the excessive weight caused the column 

 to puncture the pier through its entire length, coring out and 

 completely crushing the brickwork contained between the two 

 anchor-rods, representing an area of about 14 or 15 ins. square. 

 Immediately below this core, the brick footings were intact, 

 and a solid section 14 X 15 ins. was buried or driven into the 

 bearing-soil of clay. The masonry around the column, which 

 had penetrated into the solid masonry about 3^ feet, was not 

 crushed, but was ruptured radially along the cement-mortar 

 joints. Before the failure the piers were tested both with an 

 engineer's and mason's spirit-level, and were checked as being 

 truly horizontal and of the same height. The resistance offered 

 by the subfoundation-soil to the penetration of the 14 X 1 5~in. 

 section of footing course might be considered as amount- 

 ing to IO tons, and to that extent reducing the weight applied 

 as downward pressure at the initial moment of rupture ; under 

 this supposition, the ultimate bearing of the masonry was 100 

 tons ~ 4. 5 = 22.2 tons. Although 45 days had elapsed 

 since the completion of the piers, the cement-mortar in the 

 centre of the pier had not fully hardened and was rather 

 crubbly, although that exposed to the atmosphere nearer the 

 surface was well set and very tenacious. After the failure 

 the piers were torn away and new foundations, built upon the 

 original dimensions, were substituted, and upon a 24 X 24-in. 

 cast-iron cap the structure was built according to original 

 design and has been perfectly stable during the past two years. 

 Concrete Foundations. In general engineering work, con- 

 crete is a most useful material. It is formed of broken stone 

 from f in. to 2 ins. in longest diameter, of gravel, broken 

 brick, shells, etc., the voids of the mass being filled with 



