Plymouth Breakwater

Plymouth Breakwater is a stone breakwater protecting Plymouth Sound and the anchorages near Plymouth, Devon.

It is nearly a mile long (1,710 yd, 1,560 m), 43 ft (13 m) wide at the top and the base is 200 ft wide). It lies in about 30 ft of water. Around 4 million tons of rock were used in its construction.

In 1806 Lord St. Vincent commissioned John Rennie and Joseph Whidbey to plan a means of making Plymouth Bay a safe anchorage for the Channel Fleet. These plans may have been taken from ones made by George Matcham. Whidbey was appointed Acting Superintending Engineer. Nearly 4 million tons of stone were quarried and transported, using special ships designed by the two engineers.

The foundation stone was laid on 8 August 1812. John Rennie died in 1821, and Whidbey continued to work on the breakwater and other engineering projects until retirement around 1830; the work was completed by Rennie's sons, George and Sir John.

The above information is condensed from the Wikipedia entry.

The main contractors were I. and W. Johnson. Johnson and Brice?

A source shows some of the appliances used in setting the masonry. These include a large travelling (gantry) crane running on two sets of railway tracks on a temporary wooden structure. Between these rails another track was laid to transport materials, including the stone blocks which would be lifted and placed by the crane. The wooden crane had two A-posts supporting a long beam which extended beyond the width of the breakwater. The beam was supported by props and braced by iron rods attached to the top of the A-frames. Travelling winches on top of the beam were used to lift and place the blocks and also to raise and lower a diving bell. Another drawing shows a diving bell placed by a 'hammerhead' crane.

c.1863 Henry Lee and Son were contractors for construction of the fort.

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