152 ANNUAL REPORT 
ls & Shan CERN DITO = a DARE AUST: BUNNY STORE eR OETRIEY =. i PILI = S 
5/2 = hh 4 8 
deel hea | 
Fig. 89,—Mansard Roof and Attic Floor, W. C. Sheldon’s Residence, New York. 
CHIMNEYS. 
Figure 9o illustrates the tallest concrete chimney in the United 
States. It was erected in 1902 for the Pacific Electric Railway Com- 
pany’s power house in Los Angeles, Cal. It is built of steel concrete and 
is 180 feet high, 18 feet in diameter at the base and 15 feet in diameter 
above the shoulder with an interior diameter of 11 feet. It is built of 
two shells; the outer shell is 9 inches thick for the bottom third of its 
height, 6 inches thick for the middle third and 5 inches thick for the 
top third; and the inner shell, which is to provide for the expansion and 
contraction due to the heated gases from the boilers, has a bottom 
thickness of 5 inches and a top thickness of 4 inches. It is designed 
to give draught capacity for a 6,000 horse-power plant. The two 
shells have no connection with each other. The material was mixed by 
machinery upon the ground and hoisted through the interior to the scaffold 
which was arranged to be extended readily after each day’s work. An 
exterior scaffolding was swung just below the working forms to catch 
