1 88 TOWERS AND TANKS FOR WATER-WORKS. 



popular form for manufacturers, and it is undoubtedly true that 

 for these reasons closer figures have been obtained and broader 

 competition secured when this class of bottom and connections 

 have been specified. In the recent past nearly all of the smaller 

 water- works tanks have had the conical bottom except those 

 designed and erected by the structural works making a specialty 

 of the spherical type as hereinbefore mentioned. To offset 

 its advantages, it has other faults beside those of indeterminate 

 stresses, and necessity for heating and flanging its segments, 

 principally structural reasons, as, for instance the difficulty in 

 driving a few of the rivets in the radial seams of the bottom and 

 the vertical seams of the cylinder; besides there is a difficulty 

 in painting in the angle between the bottom and the cylinder. 

 The first coat would probably be properly applied, but this in- 

 accessible and out-of-the-way recess would very likely be sub- 

 sequently neglected, exposing this vital point of the structure to 

 corrosion. 



Notwithstanding these facts, with the exception of the Fair- 

 haven tank, which is hardly a satisfactory type, no failures 

 have to this time been reported, and such towers have generally 

 proved entirely satisfactory. In one of his own designs (Fig. 53) 

 the author has combined the two types, using a spherical segment 

 for the section of the bottom intended to be riveted to the tank, 

 which segment is tangent to a cone-shaped lower section, termi- 

 nating at the orifice. 



The Circular Girder. In the theoretical discussion of the 

 circular girder it was shown that the stresses produced were a 

 vertical shear, a torsion moment, and bending moments between 

 and over points of support. Since the maximum stress is the 

 bending moment over the point of support, in the consideration 

 of the girder, the shear and torsion stresses are not generally of 

 prime importance, although all of the stresses produced should 

 be given attention. These stresses have been analyzed and 

 tabulated for girders having from four to twelve points of 



