Polly brought tea, unasked, and stayed in the corner with her mending, which was Polly's notion of a chaperone, and was in the circumstances not a bad one. The rain came down outside. Captain Leventhorpe sat at one end of the parlour table with his back very straight and his hands round the cup, and told her about the Abrolhos.
"You spoke of them last night," he said. "I thought for a moment you must know. But of course you could not." He looked at the tea. "In the spring of the year thirteen, I was first lieutenant of the Halcyon, thirty-two, on the Brazils station. We were bound up from Rio to Bahia, and we had a long spell of thick weather, eleven days without a sight of anything. Then it cleared, one evening, a little before dark, and there was the moon and Spica as fine as you like, a hundred and eighteen degrees apart; and the master was sick in his cot, and the captain told me to take the lunar."
"And you used your uncle's method."
"He had sent it to me in manuscript the year before. Just the rule, and an abridged form of the tables, for trial at sea. He wanted a sea-officer's report of it. I was proud of it, Miss Penrose. I was proud that he should send it to me. I used it every night I could." He turned the cup a quarter-turn on its saucer. "It put us forty miles to the eastward of the bank. We stood on under easy sail. At four bells in the middle watch the leadsman found eleven fathoms, and then nine, and then seven, coral, and we came about in the dark with the breakers so near we could hear them over the wind. In the morning we could see the reef from the masthead, very low and white, two miles to leeward. Nobody was lost. The captain wrote that the currents on that coast were notoriously uncertain and that the ship had been set to the westward in the thick weather by a stream of unusual strength. I believed it. We all believed it. It is what one does believe, at sea."
"And now?"
"Now I have worked that lunar again last night by the rigorous method in Maskelyne, from the figures in my journal, which I have kept. And then by my uncle's method with your sign. And then by his own." He took a folded sheet from his breast pocket and laid it on the table. "By the rigorous method, we were not forty miles from the bank. We were twenty-seven. By his rule with your sign, we were twenty-eight. By his rule as printed, we were forty-one. Thirteen miles, Miss Penrose. The current that set us on the Abrolhos was thirteen miles of chalk."