On the evening of November 27th, 1761, nine days out of Spithead, the Deptford’s navigator pulled up the chip log himself and scratched a few notes on a slip of paper. Some deckhands peered over his shoulder as he wrote out his equations. They nodded in approval of what they spied.
“What’s it say?”
“I don’t know, I can’t read. I thought you knew.”
“Blast it! All I bloody know is that if we miss Madeira, there’ll be nowhere else to restock our bloody beer and we’ll be stuck drinking nothing but bloody water all the way across the bloody Atlantic!”
“That cookie... I told him that beer was off when he loaded it. I’ve got a nose for that, you know...”
The navigator glanced at the pair and shook his head. Slipping the paper into a breast pocket, he made his way to the captain’s cabin and knocked at the door.
“Captain?” he queried and poked his head through the doorway.
“Ah, enter, sir,” a voice called, “Mr. Harrison here was just telling me that we’ll reach Porto Santo by sunrise... I’ve been trying to tell him that I’ve been sailing this route for years and we’re still a day and a half away. What say you?”
The navigator studied the chart and the dead-reckoning marks he had earlier laid out. He cleared his throat before he spoke.
“Mr. Harrison, I agree with the captain. Your father’s little clock there has put you in error of over some 100 nautical miles.”
At 6 a.m. the next morning, the alcohol-thirsty look-out’s “Land, HO!” awoke captain Digges from a restful sleep.
“I’ll be,” he mumbled.
This first test of the marine chronometer built by John Harrison was successful. Exact knowledge of longitude was now within the grasp of the modern seaman.