The accompanying sketches show a 100-ft. chimney designed in accordance with the principles laid down on p. 119.
Assuming that it is for five boilers, each 30ft. by 7ft., and of about 50 horse-power, the chimney must be sufficiently large for 250 horse-power. The area in square inches = 100 horse-power sq.height = 100x250/sq.100 = 2500; and this corresponds to a circle 4 ft. 8 1/2in. or, say, 4 ft. din. diameter. If the firebrick be not carried up to the top, the common brickwork will need to be 4 1/2 in. thicker in each length. In Lancashire and the North of England generally the brickwork would be measured up and given as: x superficial yards common brickwork, 9in. thick, the price being about 5s.; x superficial yards extra for circular work about oft. radius, at about Is. 4d.; x superficial yards (face measure) building to batter of 3 in. in 10 ft. at about 6d.; x superficial yards firebrick lining, half-brick thick, at about 4s. 6d. x superficial yards extra for circular work about 2 ft. 4 1/2 in. radius, at about 2s.; x superficial yards (face measure) for building to batter of 3 in. in 10 ft., at about 4d.; x lineal feet building in stone basecourse, at about Is. x lineal feet neck mould, two courses deep, circular, at about 8d.; x lineal feet oversailing to chimney cap, sixteen courses deep, circular, at about Is. 6d.; x lineal feet setting stone coping at about Is. Fair prices for labour only would be for common brickwork, about 2s. 6d. per square yard, extra for circular about 8d., per superficial yard of batter about 4d.; per superficial yard firebrick lining, about Is. 6d.; per superficial yard extra for circular work, about 8d.; batter in firebrick lining, about 3d.; per lineal foot building in stone base, about 4d.; per lineal foot neckmould, Id.; oversailing sixteen courses deep, about Is.; stone coping, 1d. In addition to these the master bricklayer should add sums for labour to cover hoisting, alteration of scaffold, etc. Fig. 1 shows half elevation. Fig. 2 half section, Fig. 3 plan at All, Fig. 4 plan at CD, Fig. 5 vertical section of flue at (; H, Fig. 6 plan at E P. In Fig. 6, letter I indicates the flue from the boilers.
Fig. 5. Design for 100-ft. Chimney.