Nineteenth-Century America’s Numbers Man
If there is one reason that Nathaniel Bowditch’s New American Practical Navigator, first published in 1802,
became the standard American maritime manual, it was the accuracy of its navigational tables.
Yes, as a replacement for the old standby, Englishman John Hamilton Moore’s New Practical Navigator, Bowditch’s work held patriotic appeal.
And it was true enough that Bowditch’s Navigator was clearer and better organized than Moore’s, even if most of the text was essentially the same.
But it was the numbers that sold American mariners on Bowditch.
The unprecedentedly reliable tables, keyed to the mathematically regular movements of heavenly bodies, allowed mariners to establish their position at sea with certainty.
Bowditch didn’t create these numbers, of course, as they were based on the universals of mathematics and astronomy, as were Moore’s.
But, being a numbers man, Bowditch reworked tens of thousands of calculations and discovered no fewer than 8,000 errors in Moore’s published tables.
Despite the fact that it had been the most popular navigational text since it was first published in 1772,
it was no secret that Moore’s numbers couldn’t be trusted; in 1791, Thomas Jefferson wrote that “the later edns. are so incorrect as to be worth nothing.”
1 In welcome contrast, you could stake your life on the accuracy of Bowditch’s numbers.
Many mariners did, and theyand their cargoes-made it to their destinations safely.
To Bowditch, the precision of numbers and the regularity and predictability of the solar system offered more than reliable navigational data.
They inspired a vision that extended beyond the sea and the sky to dry land. In fact,
if we know Bowditch only as the author of the Navigator-or even as an astronomer and mathematician of some note-we are missing out on what made the man tick, and his even longer lasting and broader legacy.
It was a temperamental commitment to numerical precision that would guide all his endeavors and launch Bowditch on his nautical publication project.
The Navigator grew out of his mission to correct Moore’s tables of numbers. Think for a moment about what was involved.
These numbers had first been generated by people termed “computers,” toiling away with pen and paper.
Sophisticated mathematical knowledge was not required; patience was.
“Nothing can exceed the tediousness and ennui of the life the assistant leads in this place,” wrote a computer at England’s Greenwich Observatory in 1809.
“He spends days, weeks, and months in the same long wearisome computations.”
2 It seemed impossible that such endless drudgery could produce perfectly accurate results, and in fact it could not.
“I wish to God these calculations had been executed by steam,” exclaimed English mathematician Charles Babbage, mindful of how inhumane the labor was and how many lives and how much treasure rode on the reliability of nautical tables.
3 By 1833, he had designed the first mechanical computer for precisely that task.
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