Bui. 852, U. S. Dept. of Agriculture. 



Plate XI. 



Fig. I. — Interior, Conduit No. 2, Ontario Power Co., Niagara Falls, 



Ontario. 



Note from te::t that form scars were chipped, down; then whole surface rubbed down with carborun- 

 dum bricks. 



Fig. 2. — Minimum of Erosion by Clear Water. 



After eight years' service the conduit shown in figure 1 has not been eroded sufficiently to obliterate 

 paint marks made on walls in 1910. As velocities reach 28 feet per second, this is remarkable 

 evidence that good concrete does not erode under sliding contact with clear water. This view taken 

 March 31, 1918. 



