We started out in Penobscot Bay and the Castine Peninsula, the scene of the battle. A four-month search turned up the hulls of two twentieth-century ships and some nineteenth-century rigging but no American warships. During the last week of our venture, though, Pearson came upon oak-rib partitions that turned out to be the remains of the H.M.S. Providence , a small transport ship scuttled by the British during the height of the engagement to keep it from falling into American hands.

We kept diving for the next two years and found nothing. We had worked our way upriver to the town of Frankfurt, where Paul Revere abandoned his ship, Spring Bird , when word of our search reached an elderly Bangor resident. She told me that she remembered the hulk of Commodore Dudley Saltonstall’s thirty-two gun flagship, Warren , lying about a hundred feet offshore near her childhood home of Winterport.

It was winter by now, and we had to wait for the spring thaw. As soon as the water was warm enough, we descended on Winterport with two amphibian vehicles, eight divers, support crews, and all sorts of electronic equipment. The divers had to cope with near-zero visibility due to pollution, heavy silt deposits, and the detritus spewed into the river by the hundred-year-old lumber industry. We had powerful underwater lights to cut through the murk, but we found little of historical value. It appeared that nature and the British had stripped the sunken relics.

At last, however, our long search paid off with the discovery of a bronze six-pound cannon, still shiny after two centuries under water. The design emblazoned on the barrel [above] made it possible for us to identify the gun. Revere, under orders from General Washington, had established armament foundries in Massachusetts and sketched the emblem that marked the Bay State’s cannon. This design is still featured in the seal of the Commonwealth of Massachusetts.

The Revere cannon is one of