TIDAL POWER TUENBULL 537 



surplus power from the plant to the high levels that exist on the 

 peninsula (315 to 570 feet), there stored in reservoirs, and then used 

 at suitable times, with these high heads, by means of a pipe line to the 

 parts to be excavated. 



TYPE OF DAM 



The next figure (No. 7) shows the approximate profile of the 

 western and eastern dams; since it would not be policy to attempt 

 to get the extra power that spring tides would give, the western 

 dam need only have the height of high water, ordinary neap tides, 

 but the height of the eastern dam would have to be carried up beyond 

 the highest probable spring tides to insure that the low level basin 

 was never flooded at high tide. The figure shows this dam carried 

 3 feet higher than the highest spring tide that occurred during a 

 period of 15 years. As before mentioned, the tops of the dams 

 could be utilized as highways and would thus be of invaluable local 

 benefit, and a light steel structure is indicated on the western dam 

 for this purpose. The masonry width called for by the calculations 

 would not be sufficient for a roadway, but a light steel structure 

 could be winged out on top of the dams and made of sufficient width 

 to carry a good roadway, an electric tram, and the power-transmis- 

 sion lines that would go both west to St. John and east to Halifax. 



The flap gates for filling the high-level basin and emptying the 

 low-level basin are indicated in the sketch profile. They should 

 present no engineering difficulties, but they should be designed of 

 sufficient size to readily pass the full volume of water required by 

 the final and maximum development. 



We now come to the question of the river bottom and the location 

 of rock for a good dam foundation, and I regret that I can not give 

 any exact data. In the summer of 1919 I went twice to Hopewell, 

 but could only obtain indirect evidence as to the depth of the rock 

 under the muddy beds of the two rivers. The full line of the pro- 

 file shows the depth of the top of the mud, according to the Admir- 

 alty chart, and there is strong presumptive evidence that the top of 

 the rock does not lie more than 15 to 20 feet below this. Where the 

 " new wharf " was built at Hopewell the mud soon washed out for a 

 depth of 12 feet, when hard bottom was reached, and the outcropping 

 of ledge rock at the mouth of the Memramcook, as shown on the 

 chart and profiles, indicates the rock bottom for a quarter of a mile 

 is very near the surface. The shores at Hopewell, Fort Folly Point, 

 and Coles Head are all rocky, and the nature of all rock in this 

 locality is the same, viz, shaley sandstone to pure sandstone suffi- 

 ciently sound for making grindstones. 2 



2 The water-power branch of the DomiDion Government is to make borings and other 

 investigations at the site of the proposed dam this coming summer (1924). 



