It was supposed to have been the last full day at sea for this amateur navigator using 16th- and 17th-century replica instruments to track an Atlantic crossing under sail.

I was below decks the morning we crossed into the time zone relative to the Prime Meridian in Greenwich, England. Then it hit me: I was late for my final noon sight of the sun. I flew on deck and began my sights with a sinking heart. I had missed the critical moment of meridian passage.

I'd blown it after all these days! I continued to take readings, looking at the curve of the sun, which allowed some extrapolation back to the high point, but without the accuracy I should have had so close to a critical landfall.

I made a guesstimate of noon altitude. When I compared it with Royal Clipper's official GPS position, I was a full 63.9 miles too far to the south. I noted in my logbook that "had my error been to the north we might have seen the island, but it was south over a degree...In the 17th century, I would have deserve a flogging within an inch of my life."

Barbados is a low island and only at the northern end does it rise high enough-1,000 feet-to offer much visibility at sea. I would have certainly missed the island and sailed on into the arc of the Caribbean Sea. There were other islands there to be sure, but not the one which would have been my cargo or passengers' destination.

The next morning, I woke early to see the loom of Barbados come over the horizon. A thousand lights on the island's hills lit the low, overhanging clouds with purplish glow. Light pollution for the stargazer, they make it easier for modern sailors to approach land from a distance. Toward the south, at sea, the sky was still black and morning constellations stood sharply in relief, bright and defined, unlike much of urban North America's heavens hampered by nightshine.

Later on deck near the hawse pipe, I was startled by a roar as the massive chain with 10-pound links that the pipe houses was hauled to the sea floor by an anchor let go.

In the 17th century, the hawser was a thick, plaited cable of hemp fiber that flew out behind the anchor. Each time the anchor was recovered from an anchorage, a boy with a sharp hook stood below decks in the cable tier beneath the windlass and where the cable-fouled with marine growth or thick with smelly harbor mud or possibly sewage-snaked down from above. His job was to drag the wet line to and fro so it lay in orderly flakes (curves). Stowage had to be orderly because when the anchor was let go, this line leapt out at high speed and any kink could hopelessly jam the hawse pipe.

This could cause the anchor on a large ship-an extraordinarily heavy instrument-to suddenly brake and perhaps snap the cable, leaving the ship with no means to moor itself. This happened often enough from chafe or rotted cable.

Earlier on the voyage, I had seen anchors recovered from the Moroccan harbor of the Bou Rag Rag that spanned the whole of history. The bottoms of many Caribbean and Bahamian harbors have anchors as old as 400 years clearly visible through the waters. I've even seen modern yachts moor directly to the still functional rings atop their shanks.

At sunup, Royal Clipper anchored off Bridgetown. Aloft, on the main crosstrees was the bright yellow rectangular international signal flag for "Q" or quarantine.

Our sick passenger off the Canaries had caught up with us. Meningitis-which later turned out not to be the case-had been mentioned in an early message that was transmitted from Tenerife to Madrid, to the Spanish Department of State, to the Embassy on Barbados, to the Barbadian Health Department and finally to some minor official in the Port of Bridgetown. The result was a radio message: "You may anchor, but you may not land."

The woman, we already knew, had a post-operative infection now cured, and was home with family. This outcome was purportedly faxed to Barbados long ago. But there we were, stonewalled, with the clock ticking toward at least a hundred airline reservations from Barbados to destinations in the United States and at least a half dozen other countries.

Capt. Klaus Muller had provisions to take aboard and was champing at the bit. Meanwhile new passengers were waiting to come aboard that day for the ship's first Caribbean cruise of the season.

Medical officers from Barbados sauntered aboard to appraise our health. Hours passed before the ship was allowed to lie alongside the quay although no one could disembark. The ship's owners flew out the line's regional vice president to break the deadlock.

These precautions have historical precedent. Before the germ theory of disease was understood, terrible plagues could enter virgin territory via ships.

Pocahontas, returning to England on Samuel Argall's ship, Treasurer, died suddenly of a malady that anthropologist Helen Rountree believes could have been a bacterial dysentery. She was buried at Gravesend on the Thames, in England. Her grieving husband, John Rolfe, sent their son, Thomas, who was also sick, ashore to family lest he, too, perish on the voyage.

When Treasurer and two other ships returned with Rolfe to Jamestown, people in the settlement began to die at an increased rate. It was widely believed that these ships were the carriers of some form of bacterial dysentery, which killed many colonists over the subsequent months before running its course.

The correlation between ships and illnesses began to be understand in the early 17th century.

The poet, Sir George Sandys, who became the colonial treasurer of the Virginia Company and sailed to Virginia in 1621, was also a noted world traveler. In 1615, he wrote that a ship was "not to suffer any to traffique with or come ashore before they have a Pratticke from the Signiours of Health."

By the 19th century, the process of quarantine, inspection and granting of "pratique," or a clean bill of health, was a vital innovation. There is a shallow bank off New York Harbor where ships with communicable illness-like cholera-aboard were held at anchor. It is called Cholera Bank to this day.

Royal Clipper's passengers were in full health. Two Bahamian medical people lined us up to sign a document and-in their presence-take a single tablet of the antibiotic Ciproflaxin. Some recalcitrants hid in their cabins, delaying the whole process.

It was dark before we were finally allowed to file down the gangplank, dragging our bags onto a long unlit mole separating the harbor from the Atlantic. There were puddles in deep rutted concrete from rain that had fallen earlier. Along the wall, I saw a woman, alone, holding on to the wet blocks and creeping step by step.

This German passenger, a stroke patient, had been slowly recuperating during the voyage. Her husband had gone ahead to get their passports, assuming a van would come out for her; none did. She spoke only German and was alone, and terrified.

I took her arm and bag, and together we crept toward the other passengers in the distant terminal fighting to regain their passports and get ashore.

The incident reminded me of immigrants to the New World over the last five centuries, and how hopeless and lost they might have been, themselves near death from illness with no one to help or care for them. Many might immediately be indentured on some plantation for years-or face the horror of a lifetime of enslavement.

With our flights long gone and countless rebookings to be worked out in Bridgetown, the company made arrangements for good meals and lodgings.

This offered me an opportunity to look around Barbados, my first visit since my early years as a biologist more than 37 years ago.

Farther east than most of the Windward Islands, Barbados was one of the last islands to be discovered. Despite their distance from each other, Sir Josiah Child, and English merchant, and governor of the East India Company in the 17th century, lumped Barbados and Virginia together when he wrote: "Virginia and Barbadoes were first peopled by a sort of loose vagrant People, vicious and destitute of means to live at home, (being either unfit for labour...or had so misbehaved themselves by Whoreing, Thieving or other Debauchery, that none would set them to work)."

Tools & Trials

At the end of the day, navigating with what was jokingly called my "primitive stick," I ended up with an average daily error of a bit less than 31 miles, sometimes south but more often north of the Royal Clipper's true position. These errors are not cumulative: Each day, using the sun, this instrument offers its user a new chance to determine latitude, so that overall, one could correct individual misreadings, allowing one's ship to continue to home in on the objective.

On a small ship in the 17th century, a man on lookout at the masthead would have been able to see a little more than 20 nautical miles and in clear weather, he should have been able to easily see an island with any reasonable height.

In reality, though, islands hide in the refraction of a white, salty haze and quickly become dim with distance.

I watched Hierro in the Canary Islands disappear into mist while its fading profile was still far above the horizon.

It is also certain that had this ship been under my control, because of my error on that final day, it would have missed Barbados.

Meanwhile, fuel costs for the world's merchant fleet have tripled in the last few years and has stimulated interest in at least assisting ships with auxiliary sail power.

This winter, the 433-foot Beluga Skysails completed a wind route passage similar to that of Royal Clipper while deploying a 3,890-square-foot parasail to assist its engines. This was expected to cut $1,600 from daily fuel costs.

On the other hand, fuel costs were not a consideration to 14 men who, in January, rowed their high-tech, 50-foot boat from the Canaries to Barbados in 33 days. Their best day's run was 117 miles-under oars.

For comparison, the Royal Clipper took about 11 days to cover the same distance.