CHAP. X. PLYMOUTH BREAKWATER. 255 



anchor there, as well as to increase the security of Ply- 

 mouth inner harbour, he considered that another method 

 might be adopted, with greater certainty of success, at 

 much less cost, and without any risk of silting up the 

 entrance of the harbour. 



It may here be explained that, in its original state, 

 there were three channels of entrance into the Sound : 

 one on the west side, 3000 feet wide, between the Scot- 

 tish Ground rocks and the Knapp and Panther rocks ; 

 another, on the eastern side, 1800 feet wide, between 

 the shore and the Tinker, St. Carlos, and Shovel 

 rocks ; and a third in mid channel, also about 1800 feet 

 wide, which was rarely used, being through dangerous 

 rocks on either side. Any works which might be con- 

 structed across this middle channel, it appeared to Mr. 

 Rennie, would be of no detriment to the navigation 

 of the Sound. On the other hand, by narrowing the 

 passage through which the tidal waters flowed in and 

 out, the tendency would be to increase the scour, and 

 consequently to deepen the two remaining channels 

 an object only second in importance to the protection of 

 the harbour itself. His plan, accordingly, was to form 

 a breakwater across this middle channel by throwing 

 into the sea large angular blocks of rubble, of from 

 two to twelve tons each, leaving them to find their own 

 base, and to continue this process until a sufficient mass 

 had been raised to the level of half-tide, so as to make 

 a ridge, about 70 yards broad at the base and 10 yards 

 at the top, these dimensions to be afterwards varied 

 and increased according to circumstances. He proposed 

 that the Breakwater should be of a total length of 5100 

 feet ; of which 3000 feet, forming the central part, was 

 to be in a straight line across the Sound, and 1050 feet 

 at either end inclined inwards at an angle of 160 

 degrees. It was also proposed to run out a pier of 2400 

 feet, in two arms, from Andurn Point, at the south- 

 eastern entrance to the Sound, but this part of the 



