The Delfe Treasure

17. To Sea

Wednesday, 5th August 1733

Mid-morning on the first Wednesday in August, Elizabeth lay with jibs and mizzen sail hoisted and slack, awaiting the tide. When Aldrick saw the ebb well begun, he ordered the last of the mooring lines let go, then he turned to the Master. "Sheet in the jibs and the mizzen, Mister Moore."

"Aye, Sir. Sheet jibs and mizzen."

As the crew followed barked orders, the gentle southeasterly breeze filled the sails, moving Elizabeth slowly away from the shipyard wharf toward the opposite bank of Deptford Creek. Satisfied, Aldrick said to the helmsman, "When you have steerage, keep us centred in the creek."

"Aye aye, Sir. Centred in the creek."

When the ship had gained sufficient way for the rudder to be effective, Aldrick again spoke to the Master, "Unfurl the fore and main topsails and sheet them, Mister Moore."

"Aye, Sir, The topsails and sheet." 

Aldrick conned the ship down Deptford Creek and out into the Thames, and when he had her steadied in the downstream current, he turned to his First Officer. "Your ship now, Mister Wilson. I shall be at the taffrail." 

"Aye, Sir. I have the watch."

Once he had passed the control of the ship, Aldrick walked aft to join Elizabeth and Judith at the taffrail seats, a broad smile filling his face as he arrived. "And that, ladies, is how it is done."

Elizabeth nodded. "Yes, I see why you said it would be too complicated to explain. It would indeed be different for each set of conditions." She nodded toward the two men farther along the rail. "They appeared so intense I dared not interrupt to ask what they are doing."

"This is how we measure our speed through the water. The one has a minute glass, and the other counts how many knots are pulled through his hands. There are six thousand and seventy-six feet in a nautical mile, so we tie a knot in the line every hundred and one feet. The number of knots that the drogue pulls off the reel in one minute is the speed of the ship in knots — nautical miles per hour."

She nodded again. "And the timekeeper chalks the number onto the slate while the line handler reels in the drogue."

"Exactly! And the faster the ship's speed, the smaller the drogue, else it would be too difficult to retrieve."

Elizabeth pointed to the men beside the helmsman. "And those two maintain the transit board you had explained. The one tends the sand glasses and the other the course steered." She bobbed her head. "Speed, time and direction give position."

"Yes, a component of it, but is necessary to also account for tidal flow and ocean currents." He pointed to the embankment. "See how the water moves in relation to the land. We are moving through a waterway which itself is moving, so for increased accuracy, we must factor in the speed of the water."

"How do we measure that?"

"There are now tables compiled with observations, but this is moot when we are within sight of land. Here, we can take compass bearings of identifiable points and plot them on our chart. Where the lines cross is where we were at the time of the sights."

A broad smile spread across Elizabeth's face. "And sequential crossed lines along the way will tell us our course and speed."

"You learn well."

"You teach well."

Judith interrupted the moment with a comment. "George told me it is wise to remain within sight of land for this reason — as long as it is safe. But when the weather turns, it is best to move farther offshore."

"Aye. Wise words." Aldrick pointed to the riverbank. "The danger is not at sea; it is the land. A prudent mariner always leaves sufficient sea room to manoeuvre safely if the weather turns quickly adverse." 

As they followed the sinuous course of the Thames, Aldrick answered questions from both Elizabeth and Judith, and he explained what was happening aboard. When they passed the Royal Hospital for Seamen at Greenwich, he pointed to the huge clock in the tower. "Of habit, we set our time to that, and from then onward, our reckoning is from the repeated turning of sandglasses, four-hour, one-hour, and half-hour, and the recording of the progression in the log." 

"By the clock, it is at twenty past ten, so there will be a twenty-minute error."

Aldrick laughed. "Twenty minutes is minor. We will accumulate that much and more in a few days of dour weather with glass and turning errors. But the timekeeper will adjust now with a ten-minute glass."

"Ten minutes? Not twenty? So toward the end of the voyage, have we no idea of the accurate time?"

"Oh, we do have. Those lunar tables we copied should allow us to adjust from a complex series of calculations at each clear moon sight."

His explanation of the theory and the method was interrupted by the pealing of the ship's bell. "There, he has turned a new half-hour glass and marked five bells of the forenoon watch."

Elizabeth nodded. "And the pattern makes it easier to count. Ding-ding pause, ding-ding pause, ding, is easier than five in quick succession."

"Indeed. Clarity and ease of understanding are important."

"Particularly with the higher numbers. Beyond a dozen, many would lose count. Surely they do not go past twelve."

"No, the watches are four hours each, so the end of watch is eight bells, then when the next watch takes over, the count begins again." 

Five hours later, Elizabeth emerged from the Thames as the tide neared low water slack. Aldrick conned the ship onto her starboard anchor close to the marked shoals off the mouth of the Medway, and when they had settled, he asked for eight bells. As they pealed, he tossed a garland of roses onto the water and bowed his head.

The long silence which followed was broken when he said in a voice for all to hear, "For Father. For all of our fathers and grandfathers. For all of those who have passed before us. We are the next watch. Let us not disappoint."