90 ANNUAL REPORT 
The following table gives the cost for various portions of this work: 
TABLE No. 19. 
Cost of Breakwaters. 
Superstructure |Concrete blocks | Mass concrete 
per lineal foot. | per cubic yard. | per cubic yard. 
Old U. S. Breakwater, solid | 
concrete superstructure, 1889 POSS) eo aicasco eas: $9.19 
Old U. S. Breakwater, solid 
concrete superstructure, 1891 HOE || sg odbc oes oo 8.21 
Old U. S. Breakwater, con- = 
Crete chelsea ae (2.26 $ 6.64 6.64 
North Breakwater, 36 foot sec- 
tlOns ss Pal oaieecntenes 56.34 7.10 5.65 
North Breakwater, 24 foot sec- 
tLON Lee ween eres cso 46.02 7.10 5.65 
South Harbor, concrete shell) 
SUPCESELUCTUNC Ht ae meet 108.49 10.00 9.40 
Concrete wharves, piers and river jetties have also been constructed. 
The Eads’ jetties at the mouth of the Mississippi River are for a portion of 
their length of concrete, an illustration being given in figure 37. 
SEWERS. 
During the last few years concrete has been used in increasing quan- 
tities for sewer construction. The first use of concrete for that purpose, 
in this country, appears to have been in 1891. The Waring Sewer Pipe 
Co., of Providence, R. I., patented during that year a,method of manufac- 
turing sewer pipe in sectional pieces. They cast it in smooth iron molds, 
the invert and arch, separately. The invert pieces were rabbeted or 
grooved at the ends so that when two pieces were laid end to end the 
groove could be filled with mortar. 
The arch pieces had beveled shoulders which fitted snugly upon the top 
edges of the invert; the arch joint being plastered over with mortar from 
the outside. Lateral connections were made through specially molded 
junctions. The 4-foot main sewer, in Middlesborough, Ky., was con- 
structed by this company, the invert being built in place. The cost, ac- 
cording to the construction company, was 25 per cent cheaper than brick 
sewers. ae ) 
In the same year A. C. Chenowith, C. E., invented a seamless concrete 
duct which was applicable either to sewer or electric duct service. The 
first piece constructed was for electric ducts in Yonkers, N. Y. A thin 
iron ribbon was wound spirally over a collapsable wooden mandrel or core, 
a bed of plastic concrete was laid in the trench and the core laid.upon this 
and then covered with another layer of concrete. The wedges were then 
taken out and the mandrel removed leaving the iron ribbon as a shell to 
support the concrete until set, when the ribbon could be readily removed. 
