but not by divers. A ship built in the third century a.d. in northern Europe, but with Mediterranean-style mortise-and-tenon joints, was found underground during the construction of a new county hall in London in 1910. Horses dragged the carefully cradled hull to the London Museum where it has remained.

The final chapter in the story of Lake Nemi also involved dry-land archaeology. Two gigantic and once lavish “pleasure barges” from the time of the first-century emperor Caligula were finally exposed in the early 1930s after Benito Mussolini had the lake level lowered twenty meters by pumping its water into another lake over a four-year period. Both vessels were burned during World War II, but records show that their hull planks were mortise-and-tenon joined and then sheathed with lead over fabric. Because the hulls lay in a freshwater lake, without the marine borers that consume wood in most seas of the world, the lead must have served as a kind of caulking. The fresh water also preserved the wooden parts of the barges’ huge anchors, providing firsthand evidence for the use of the lead anchor stocks that are so frequently found in the Mediterranean, often with lead collars that prevented the anchors’ wooden arms from spreading out from their shanks.

Draining of the harbor at Kalmar in southeastern Sweden in the 1930s revealed more than a dozen wrecks, including a well-preserved clinker-built vessel of the thirteenth century. In North America, while the Lake Nemi barges were being studied and the Kalmar harbor was being drained, the diver L.F. Haggland buoyed to the surface of Lake Champlain in New York State Benedict Arnold’s flagship Royal Savage, which had been sunk by the British in 1776 during the American War of Independence, by tying empty metal drums to the ship’s hull and filling them with air on the lake bed. The following year, in 1935, Haggland returned for the better-preserved gondola Philadelphia, which had been lost in the same battle and is now displayed in the smithsonian institution in Washington, D.C.

Unfortunately, in the first half of the twentieth century clam-shell drags were sometimes lowered from the surface to dig violently into shipwrecks in an indiscriminate search for artifacts. Such was the case in the 1930s with several of the ships scuttled in the York River, Virginia, by General Cornwallis shortly before the decisive battle of Yorktown that ended the American War of Independence in 1781. Such, too, was the case in 1950 with a Roman wreck at Albenga, Italy, where the steel claws were guided by an observer in an underwater chamber who telephoned directions to operators on the surface.

Nor were divers needed in continuing work in northern Europe in the early 1900s. In 1904, a magnificent and beautifully preserved Viking ship of the early ninth century was excavated in a female burial mound at Oseberg, Norway, only thirty kilometers from Gokstad. In England, surveyors of the partly clinker-built hulk in the Hamble River concluded in 1933 that it was the Grace Dieu, an identification corroborated by tree-ring dating of the timbers that had been taken to the Winchester Museum at the end of the nineteenth century. Also in England, in 1939, the impression of a clinker-built ship was found in a royal burial mound, probably of a Saxon king, at sutton hoo in Suffolk; gold coins among the fabulous treasures in the burial date the grave to the seventh century a.d. And in 1946, the discovery of the first of three Bronze Age, plank-built boats of around 1500 b.c., in the Humber estuary at North Ferriby in Yorkshire, began a lifetime of work for the amateur archaeologist E.V. Wright, who demonstrated how the boats’ planks were sewn (or laced) together with branches of yew.

In Egypt, in 1954, archaeologists discovered a 4,500-year-old dismantled boat in a stone pit next to the great pyramid of Cheops at Giza. After spending years fitting together over a thousand pieces of wood, Ahmed Youssef Moustafa of the Egyptian Department of Antiquities had reconstructed for display at the pyramid a river craft, nearly forty-four meters long, built of massive cedar planks that were not fastened together by mortise-and-tenon joints but were laced together, like the planks of the Ferriby boats, except with ropes instead of yew branches. Lacking a keel and mast and with only a dozen paddles, the boat was probably designed to be towed from the bank of the Nile.