But the toll dropped during the winter, and stayed low, with only 2,000 more deaths from the disease tallied through all of 1666. Then, just as it appeared that the epidemic was truly done, came the four days in September when the Great Fire of London destroyed most of what lay within the old city walls, along with some newer neighborhoods to the west. Four hundred and thirty-six acres burned; at least thirteen thousand homes were destroyed. So were 87 out of the city’s 109 churches, including old St. Paul’s Cathedral. When that giant building caught fire, the tons of lead in its roof melted, creating a river of liquid metal flowing into the Thames.
A new London began to rise almost immediately. The fire seemed to obliterate the plague, though that could well have been a coincidence in timing rather than the result of any lasting impact on the city’s rat population. Christopher Wren—often with the aid of his colleague in the nascent Royal Society, Robert Hooke—took the lead in restoring sacred London, building fifty-one parish churches along with his crowning monument: the new St. Paul’s, with its glorious and technically sophisticated dome.
Life in the capital soon returned to an approximation of its preplague normal. The savants, Hooke and Wren among them, resumed weekly meetings at the Royal Society. Their conversations overflowed into the invisible university housed in the still-exotic coffeehouses and inns of the rebuilt city. Some of that talk was more enthusiastic than rigorous: at early meetings, the Society heard reports on “a Very Odd Monstrous Calf” and “Of the Way of Killing Rattle-Snakes,” presented alongside “A Spot in one of the Belts of Jupiter” and “General Heads for a Natural History of a Country.” Newton himself took no part in that eager, hungry, small “c” catholic pursuit of new knowledge. It would take him twenty years and more to organize the results of the plague years into a fully realized body of work. He did so mostly in silence. He had some contact with members of the nascent Royal Society in the early 1670s. But he soon disappeared from the view of learned Europe. That was partly because he resented challenges to his results, partly because of his determination never to share a discovery before he was certain, and partly because for many of those “missing” years he pursued lines of inquiry that he actively wanted to keep secret: inquiry into heterodox religious beliefs and into the ancient pursuit of alchemy, which he saw as one more way to investigate change in nature. He wrote of his alchemical experiments to a handful of fellow searchers, but he rarely communicated in any public way with his fellow natural philosophers in London, and he visited the capital even less.
But such silence did not mean that he was unmoved by the same impulses driving the early Royal Society men, with their public commitment to knowledge for its own sake—and to the application of whatever could be discovered to practical uses. From the beginning, he too recognized that natural philosophy could comprehend daily life as well as the broad sweep of nature. As early as 1664, for example, before he plunged into the question of gravitation, he laid out a geometrical approach for calculating compound interest—his first contribution to the mathematics of money. A decade later, he turned his quantitative virtuosity to the service of his home institution, helping Trinity College’s bursar analyze how much rent he should charge for land—farms that the college owned. Newton could count and Newton could think, and his work here—pricing an asset that offered payments over time—already hinted at the possibility that those two skills could make a man rich.
If that thought crossed his mind in his Cambridge years, he didn’t act on it. His full immersion into the world of money—on his own account as well as in service to the crown—would come a full three decades after his miracle year, when he took up new duties as an officer of the Royal Mint. Others, though, were beginning to recognize that there might be a connection between quantitative reasoning and wealth. They would pursue both riches and yet another new discipline: a science of change over time that took not the planets but people as its object. Perhaps the most complete representative of these new men was someone much less remembered than he should be: a polymath and voraciously money-hungry parvenu named William Petty.
*For example: the geometrical definition of a circle is a curve on which every point is the same distance from a single central point, a distance called the radius. Algebra produces that same circle as the solution(s) to an equation: (x – a)2+ (y – b)2= r2, in which x and y are the coordinates for any point on the rim of the circle, a and b are the coordinates of the central point, and r is the radius of the figure.