128 ROYAL SOCIETY OF CANADA 



To verify this fact the fourth and fifth series of experiments were 

 conducted, the bottom being now constructed of grooved and tongued 

 planks laid with the joints in the direction of flow, which practically 

 eliminated the rippling. A uniform slope was also given to the bottom, 

 so that the water could escape with a maximum of freedom, while the 

 tend.eiicy to produce backwater would be diminished to a minimum. 

 Diagrams III. to X. show the results of these experiments, which in 

 every case verified the statement, that when the bottom of the river 

 at any given point A is at or below the level of the surface of the water 

 at another given point B, further down the river, the introduction of 

 any obs4:acle at B will produce backwater at A. 



The highest point of the bottom of the Ottawa Eiver between the 

 Chaudière Falls, designated A and the Little Chaudière Falls designated 

 C, is a ridge designated B, on which is constructed the O'Connor dam, 

 Eing dam, etc. Thus between B and C the river is of the character 

 of a deep pond and anything which affects the level of the water at B 

 produces the same effect upon the level of the water at C. Further, 

 the least depth of the water at the Little Chaudière Falls in 1903 was 

 found to be, at high water, about 10 ft., and the bottom of the river 

 at that point, as well as at every other point at the foot of the Little 

 Chaudière Eapids, is below the level of the ridge at B. The results of 

 the experiments show that as soon as the surface of the water at the 

 brink of the Chaudière is on a level with the bottom of the O'Connor 

 dam, any obstruction however small, introduced at A, raises the level 

 of the water at A and produces backwater at B, which again is repro- 

 duccd at C, on account of the river between B and C being practically 

 a deep pond. This holds true for the whole of the period during which 

 the O'Connor dam is submerged and therefore any wing dam introduced 

 at; A inv.st necessarily diminish the head available for power at the Little 

 Chaudière Falls. These results have also been verified by the previous 

 experiments of eminent hydraulic authorities on other rivers. 



The following tables give a summary of the measurements made, 

 the measurements being in units: — 



