Plymouth Breakwater by John Lea

 

HROUGH Mr. John Rennie, the builder of London Bridge, was the chief designer and engineer of the Plymouth Breakwater, the waves of the English Channel gave him great assistance; and unlike other workmen, they asked for no pay. We shall see presently how they worked. In 1806, the Lords of the Admiralty made up their minds, for good and all, that something must be done to make the splendid harbour of Plymouth Sound a safer place of refuge in case of storm. Mr. John Rennie and another engineer, named Whidbey, were asked to go to Plymouth and look at the Sound, and then say what they thought should be done.

The authorities took five years to make up their minds. But Rennie persistently called attention to the map of Plymouth Sound.

'If you build a long stone pier out from either shore so as to break the force of the waves,' said he, 'you will interfere with the free flow of the currents from the river-mouths, and cause them to drop the sand and soil, which they are ever carrying out to sea, until the harbour-mouth is choked by them. The harbour has been formed into its present shape by the free actions of current and tide, and if these be altered by artificial means, the shape and safety will be destroyed.' Then he went on to explain that the proper thing to do was to build a wall in the Sound itself, without letting it touch the land at either end. The tides, thus only slightly confined between the shores and wall-ends (but allowed to run in their old accustomed channels), would keep their channels free. The Lords of the Admiralty thought it all over, and on the 22nd June, 1811, issued an order for the work to begin.

Then no more time was lost. Down to Plymouth went the engineer and his staff again. They searched for a quarry to dig the stone from, and found it at Oreston, in the north-east corner of the Sound. In March, 1812, crowbar and gunpowder began to be busy there. Meanwhile, on the water of the Sound, two and a half miles south of Plymouth Town, a number of buoys were moored in two parallel lines, extending over a distance of one thousand two hundred yards, east and west. They marked the place where the great barrier was to be built, and their anchors partly lay on a reef of dangerous, submerged rocks, and partly in deep water. By the time they were safely fixed, the first shiploads of stone were ready. But ten of the ships were not like other ships. All along the deck and all down the middle of the lower part of the vessel, ran lines of rails, and on these were small trucks each carrying one large stone. The stones varied in weight from half a ton to ten tons and more. They were rough-hewn from the quarry, for as Rennie was going to let the sea build the wall, it was better that the stones should be irregular in shape. Each ship, being loaded, sailed to the line of the buoys, and, safely moored to one of them, proceeded to unload. This was done by wheeling the trucks, one after another, to an opening in the stern, where the truck was tilted on one end and the huge stone toppled into the water. The process of unloading took each ship about three-quarters of an hour. There were forty-five other ships, each capable of carrying some fifty tons of small stones and rubble. These latter cargoes were shot into the water in much the manner that ordinary ballast is unloaded.

The first large stone, marking the beginning of Plymouth Breakwater, went gurgling to the bottom of the Sound on August 12th, 1812, amid the flutter of flags and the booming of cannon. It was the Prince Regent's birthday, and Lord Keith, commander of the Channel Fleet, came to witness the beginning of the great task. The stone fell on a spot called the Shovel Rock, near the centre of the lines of buoys, and was very soon covered by rubble from the next ship. Then the procession was kept up with such diligence that by the end of the following March, the top of the pile peeped above the water at low tide—forty-three thousand seven hundred and eighty-nine tons had been dropped! Bit by bit this point of new land grew longer and longer, until it became possible for workmen to disembark upon it, and when a storm broke in March, 1814, a number of ships were glad to seek its shelter, among them being the famous warship, Queen Charlotte. So satisfactory was the protection it even then afforded, that the engineers decided to raise it higher than was originally intended, not stopping until two feet above high water was reached; thus rendering the water between it and Plymouth calm enough for small vessels.

When making his survey, Rennie had come to the conclusion that the slope of his great bank of stones, where it faced the open sea, should be at an angle of five feet to one. That is, in climbing from the bed of the sea, it should rise one foot in every length of five. But others did not agree with him, and the slope was made three feet to one, until the waves themselves took up the argument, and proved that John Rennie was right. In 1817, they broke over the bank in such a storm that large quantities of stone on the seaward side were swept over the top, and littered down the opposite side. When the gale was over, examination proved that the sea-slope was five to one. Yet for seven years more this curious dispute was kept up, and not until 1824, when Rennie had been dead for three years, did the sea at last have its way, and convince those in authority that it (and Rennie) knew what the proper slope should be. On November 23rd, 1824, so fierce was the storm that it hurled several thousands of tons of ponderous stones from one side of the Breakwater to the other. That was the final word, and the Breakwater stands to-day as the sea ordered it.

Plymouth Breakwater. Plymouth Breakwater.

When this huge pile of loose stones and rubble more than a mile long, rising from a broad base at the bottom of the sea, had been formed into a close mass by the action of the waves, a coating of masonry was laid over them. At either end, east and west, the great wall bends slightly for a short distance northward, and is finished in a circular platform of solid masonry. At the west end stands a handsome lighthouse; at the east, a beacon, and between these and the shore are the two entrances to the harbour—one a quarter of a mile wide, and the other three-quarters. The width of the wall at the top is forty-five feet, but at the bottom it is three hundred and sixty feet, and weighs nearly four million tons. Surely it would be a boisterous sea that would carry this away. Its total cost was about one million five hundred thousand pounds, and it was finished in 1848.

Before the lighthouse was built, it became necessary to warn vessels of the position of the new sea-wall, and for more than twenty years a lightship burned a signal there. This was the state of affairs when that terrible storm of 1824 swept up the Sound, and among the wrecks it caused was one of an unusual character. A small vessel, laden with cork, was nearing the mouth of the Sound, when she was suddenly struck by a violent gust of wind and turned completely over. The captain, a boy, and two passengers were the only ones below at the time, and these, finding the water rushing in, sought refuge in the ship's coal-hole, which, owing to the reversed position of the hull, was now above them instead of below. In total darkness, and lapped by the encroaching water, they floated thus for six hours. In the early morning they struck against the west point of the Breakwater, heeled over it and drifted toward the lightship. Those on board the latter, little thinking that the wreck had life on it, pushed the hull away with poles, and, caught by the tide, it soon drifted from sight. Three hours later it appeared again. The return tide had washed it back, and a little later a larger wave than usual carried it on to the rough stones of the unfinished Breakwater, where it held fast. The water receded, and the four unhappy voyagers crept out on to the rocks, to be rescued half an hour later by a pilot boat. Such was one of the unexpected services rendered by the Breakwater at Plymouth; but its expected benefits, worthily accomplished, have been too numerous to record.