240 TOWERS AND TANA'S FOR U r A TA'- Jl'OA'A'S. 



and determined by experiment. In order to allow for a mar- 

 ginal projection for the anchor-rods, the perimeter of the 

 upper plane of a conic frustum, which is a suitable form for 

 the foundation of a stand-pipe, might be that for a 27-foot- 

 diameter circle, which would allow an annular space of 18 ins. 

 around the 24-ft. -diameter tank. If such a conic section is 

 considered in cross-section, the lower base projects beyond 

 the upper with a length equal to half the difference on either 

 side, and this projection, representing the spread of the 

 masonry, is secured by offsets in the masonry courses, the 

 number and height of such offsets determining the height of 

 the figure or foundations. 



As shown, the maximum theoretical projection may be 



/R 

 -p ; and if the masonry 



is in courses of brick whose thickness, /, is 2.5 in., with a 

 modulus of rupture R, according to the table, of 800 Ibs. , 

 and a pressure at the base, P, of 2 tons, substituting these 

 values in the formula, the maximum theoretical offset is 8.3 

 in., to be reduced by the use of a suitable factor of safety. 



The maximum safe projection of brick in single courses, 

 as determined by practice and ordinance in many cities, 

 is J the length of a single brick, or a fraction over 2 ins., or a 

 factor of safety, using the formula above, of 4, which, having 

 been used in designing throughout, will be continued in foun- 

 dation work where the masonry is an almost solid monolith. 



For experiment, selecting a 44-ft. -diameter circle as the 

 required base, the projection, being the difference bet wren 

 that and the 2/-ft. diameter, or 17 ft., the projection on 

 either side is 102 ins., and the projection allowed for each 

 course being 2 ins., there are 51 projections, whose thickness 

 being 2. 5 inches, the height of the foundations is 10.6 feet. 

 From these quantities the exact total weight can be deter- 

 mined, and is as follows: 



