CONCRETE LINING FOR IRRIGATION CANALS. 
59 
extra expansion and renders the joint more impervious; it adds noth- 
ing to the bond between the sections. 
m ■ 
m 
P 
Fig. 4.— A broken joint in concrete lining, New York Canal, Boise, Idaho. 
(3) An interlocking device (fig. 3, c), consisting of a 4-inch strip 
of corrugated iron, was inserted in each joint of the lining of the 
North Side Twin Falls Canal, Idaho. If the metal strip is thickly 
