132 ROYAL SOCIETY OF CANADA 



must necessarily be reproduced at C. When this water surface rises 

 to the top of the O'Connor dam, the depth of the water at the Chau- 

 dière Falls is between 13 and 14 ft., and there is consequently produced 

 at B 13 ins. o-f backwater, which is again reproduced at C. 



On April 15th, 1902, the water surface was that shown by the 

 line E F and the depth of the water at A was about 20 ft. The experi- 

 ments show that the building of the dam in question must then have 

 produced at least 20 ins. of backwater at B and therefore also at C. 



Another important point to note is the fact that the building of 

 the dam at A produced, backwater sooner than if the discharge had 

 been left free, and thus the effective depth available for power purposes 

 at the Little Chaudière Falls is diminished for a proportionately longer 

 period. 



