prize8-3, Exercise 3: Smeaton's choices

Model answer (check the details):

The curved shape. An oak trunk is broad at the base, narrows as it rises and curves smoothly. Smeaton copied the form because a wide base gives stability and a low centre of gravity, a narrow top gives the wind and waves less to push against, and the curve lets the waves run up and over without striking a flat surface. The problem it solved was resistance to the sea and the wind, which had destroyed the earlier tall towers.

The dovetailed blocks. The blocks of granite were cut so that they locked into one another, like the teeth of a joint, and pinned with marble dowels. The problem it solved was that waves could pull apart a tower made of loose stones. Locked together, the courses held each other and the whole tower acted as one mass. The first courses were also fitted into steps cut in the rock, so that the tower was anchored to it.

Other choices: using stone in place of timber, to solve the problem of fire, and a lime that set under water, to solve the problem of mortar washing out (check).

Care: Smeaton's own account is the main source for these reasons, so they are his explanation, which later engineers accepted but which historians still examine.