1851 Great Exhibition: Official Catalogue: Class VII.: William Stuart
28. STUART, WILLIAM, M. I. C. E., Plymouth, Devon — Designer and Superintendent of the Plymouth Breakwater Works.
Model, in limestone, of the breakwater in Plymouth Sound, on a scale of 1 inch to 42 feet, with silver lighthouse and beacon, made for the Exhibition, under the direction of the Lords of the Admiralty. The breakwater was commenced on 12th August, 1812, agreeably to a Report dated 21st April, 1806, of the late John Rennie, civil engineer, and of Joseph Whidbey, a Master of the Royal Navy; and has been constructed under the auspices of the Lords of the Admiralty. Its length is 5,100 feet at the top, and about 1 mile or 5,280 feet at bottom, being nearly three times the length of the Exhibition Building. At the top, it is 45 feet wide, and has a slope to seaward of 5 to 1, and a slope to landward of 2 to 1. It is already composed of 3,768,879 tons of stone. It has been 38 years in construction, and has cost the nation about £1,500,000. The area of Plymouth Sound is 1,800 acres, and within the breakwater there is anchorage for 40 line-of-battle ships, besides a fleet of merchant vessels. The exhibitor of the model, who is the resident engineer, has been connected with this undertaking for 40 years. The lighthouse and beacon on the breakwater were designed by Messrs. Walker and Burgess, civil engineers.
Polished marble slab, on pedestals, from the breakwater quarries.
Model, in limestone, of a general section taken through a part of the centre of the breakwater, with wood-jetty and crane, showing dove-tailed stones and truck on jetty.
Model, in limestone, of a section of the breakwater, taken through the buttress and foundation of the lighthouse, with inverted arch at the west end; and showing dove-tailed stones.
Circular lewises, used in lifting and setting stones at the breakwater, invented by the exhibitor in 1808.
Model, in mahogany, of a breakwater stone vessel.
Medals of the breakwater and lighthouse, set in marble.
The breakwater in Plymouth Sound is formed by the deposit of stone in unshapen blocks of various sizes, but disposed upon a regular plan as a huge, rough, broad-based wall, mole, mound, or dike, massive enough, if it be compact enough, to check, if not wholly to stop the roll of the sea under the influence of gales of wind, and to render the part of the Sound within it a safe anchorage during gales from the south-west. The Isle of Wight is a breakwater afforded by nature to Portsmouth, and the breakwater in Plymouth Sound is the result of an endeavour to supply Plymouth with some compensation for its natural deficiencies.
The breakwater is a mass of rock-like blocks of stones deposited in a heap at random, as far as regards the placing of the blocks of stone, though the heap takes the form, in plan and section, which the model exhibits. In this circumstance, that it is a deposit and not a construction, the weakness of the breakwater consists. The blocks on the outer slope, or foreshore, are liable to be taken up singly and displaced by the action of the sea upon it, deprived as every loose block is (and the bulk of the work still consists of loose blocks) of two- fifths of its weight when immersed in sea-water; and probably no heavy sea runs into Plymouth Sound without occasioning change of place to some of the blocks of the outer slope. The blocks range from one ton to five tons in weight—a block of limestone weighing five tons being in bulk equal to a cube of 4 ft. 6 in. or a yard and a half on every side. The greatest quantity of the material is of the smaller sizes, and is known as rubble; but many blocks have been deposited of considerably more than the largest size named, and many even of these have been known to be taken up by the sea from the outer slopes and thrown upon the crest of the mound, whilst thousands of tons, have since the commencement of the work been thrown over the mound from the outer to the inner slope. It may be questioned whether the breakwater is not, at this time, from this cause, further up the Sound than when it was originally planned.
The breakwater is disposed in three connected compartments—the central, or main body, which is 1,000 yards long, and the eastern and western parts respectively, which are each about 350 yards long, above high water.
The Digue, or breakwater, at Cherbourg, opposite to Plymouth on the other side of the Channel, is, in like manner, mainly a mass of deposited rubble, but of generally smaller-sized stones. It is more than double the length of Plymouth breakwater, or about 2.25 miles.— W. H.]