Most people rightfully know Isaac Newton as a scientist. His 1687 masterwork Philosophiæ Naturalis Principia Mathematica founded classical mechanics, establishing the laws of motion and the theory of universal gravity. Newton is the most prominent figure associated with the Scientific Revolution, and thanks to his prolific written output his life is well studied.
But there was another side to him of which few are aware: in his later years, Isaac Newton worked as something of a detective. In his capacity as Warden, and later Master of England’s Royal Mint, he helped put an end to the golden age of counterfeiting, leading him into a years-long feud with the greatest coiner of his time: the audacious William Chaloner.
Born to a weaver’s family in Warwickshire, England, the young Chaloner so tormented his parents that they sent him off to Birmingham, where he was apprenticed to a nail maker. Birmingham was also England’s counterfeiting capital, and it’s likely he picked up some tricks of the trade there. Sometime in the early 1680s, Chaloner traveled to London on foot, with no job and no prospects. There he would learn the confidence tricks that would allow him to build a criminal empire.
Chaloner’s anonymous, contemporary biographer provides a scandalous account of his early years in London. He got his start selling bawdy novelty pocket watches. That business led him to an associate, with whom he undertook one scam after another. First, medical quackery, providing false cures to desperate plague patients. Then, they turned to fortune telling, and the bolder metaphysical enterprise of stealing things, then “divining” the stolen goods’ location for a fee. This venture ended abruptly in 1690, when Chaloner was implicated in a theft and forced into hiding.
Things cooled down and Chaloner soon returned to public life, trading in used clothing. All the while, however, he had been studying under goldsmith Patrick Coffee, and by 1691, he turned his full attention to counterfeiting.
This new operation would make him rich within the year. Forging pistoles and guineas, he was soon able to afford a house in the then-suburb of Knightsbridge. He hired a carriage, dressed in gentleman’s clothes, and collected silver plate. He also abandoned his family, starting affairs with other coiners.
His good fortune wouldn’t last forever. In 1692, Chaloner got word that one of his associates had been arrested. He spent the following two days frantically minting to tide himself over, then fled until his companion’s hanging. He then concocted another scheme, wherein he would pay printers to run seditious Jacobite pamphlets, then turn the printers in for a reward.
Meanwhile, those in power were beginning to notice something: England’s money was disappearing. King William III, embroiled in the Nine Years’ War against France and desperately in need of funds, could not afford to let this continue. At the time, there were two forms of legal tender: hand-forged coins struck prior to 1662, and machine-minted ones made after. Deft hands could clip thin shavings from older coins’ edges. The machine-minted coins were designed with milled edges to make clipping impossible, but even then, they could be sold in the arbitrage market. Silver bullion was worth more in France and the Netherlands than silver coin in England, so shrewd entrepreneurs could collect coins, forge them into ingots, and ship them overseas for profit.
Many offered solutions, William Chaloner included. He published a series of pamphlets accusing the Royal Mint of incompetence and suggesting a great recoinage, in which the old, clipped coins would be collected, melted down, and milled by machine, with deeper impressions that counterfeiters could not hope to reproduce. He came down hard on counterfeiters, proposing a licensing system for coiner’s tools and charges of treason for the guilty. Of course, he had no intention of making his own job harder. This was a long con. Chaloner intended to establish himself as a coining expert, in hopes of gaining access to the Mint.
William Lowndes, Secretary of the Treasury, solicited help from England’s greatest minds. One of his letters reached Isaac Newton, who also thought of a recoinage. Apparently Lowndes took his ideas more seriously than Chaloner's. In March of 1696, Newton received a letter inviting him to London to oversee the whole process as Warden of the Mint. He accepted.
There, Newton applied his usual scientific brilliance. He took careful notes on every aspect of the coining process: the amount of coal the furnace burned, the capacity of the melting pots over time, the optimal shift men and horses could turn the mill before tiring. He calculated an efficient pace for the work, overseeing repairs of old facilities and construction of new ones. Under his command, the mint went from struggling to produce £15,000 in a week to over £50,000 with ease.
There was, however, another part of the job that Newton wished to avoid. The Warden was responsible for capturing and prosecuting counterfeiters. Newton wrote to his superiors, seeing the job as beneath him. Nevertheless, on July 30, 1696, they assigned him a case: finding a set of dies (used for cutting or molding metal) that had been stolen right out of the Mint.
Reluctantly, Newton set out doing what he had always done: collecting data. He trolled the depths of Newgate Prison, offering stays of execution to those who talked. He disguised himself, going undercover to pubs of ill repute. He even spoke with Chaloner, whom he dismissed after hearing his accusations. Newton may not have wanted the job, but he was good at it. He was beginning to establish the network of criminal connections that would help him bust Chaloner’s operation.
Chaloner, meanwhile, had ramped up his claims. The Mint wasn’t just incompetent—it was complicit. The chief engraver had sold the dies to his old master Patrick Coffee and one Mr. Chandler—Chaloner’s own coining alias. In 1697, he took his claims to the House of Commons, bringing one of his own coins as evidence. The House was shocked, and ordered Newton to give Chaloner access to the Mint facilities.
Newton refused. He had legal grounds; the oath he had taken on accepting the position prohibited him from letting an outsider see the Mint’s tools. He attempted Chaloner’s suggested methods for deeper impressions, demonstrating their impracticality before the House.
The House relented. Chaloner returned to his own tricks, starting up a new forgery in Surrey and attempting to manufacture another Jacobite conspiracy. But Newton recognized him when he brought it to court, and had him arrested.
There was, however, little evidence against him. Chaloner was able to bribe one of his associates into fleeing to Scotland, and the other witnesses went silent for unknown reasons. The case was thrown out, and Chaloner was free—but his efforts to clear his name had exhausted his funds. He redoubled his accusations against the Royal Mint, petitioning Parliament for an investigation. He claimed innocence, that his imprisonment had been retaliation for exposing the conspiracy. Now it was Newton on the stand, defending himself against Chaloner. His testimony was sufficient and the claims dismissed, but the whole ordeal left him enraged.
Newton set about interviewing as many of Chaloner’s associates as he could. The truth of their testimony didn’t matter. Many crimes, even minor ones, were punishable by death, and juries were usually averse to handing down guilty verdicts absent overwhelming evidence. The goal was to implicate Chaloner in as many schemes as possible, in order to convince the jury that he had done something criminal at some point in his life. Newton spent almost all of his working days collecting evidence, taking at least 140 statements. Now, he had only to wait for Chaloner to slip up.
That slipup came in the form of forged lottery tickets. Chaloner had sold one to a pawnbroker, and when the pawnbroker was arrested, his name came up. Chaloner was arrested in 1698, and his case went to trial on March 3 of the following year, presided over by notorious hanging judge Salathiel Lovell.
Chaloner didn’t understand the extent of the charges, thinking he was only on trial for the forged tickets. As Newton’s witnesses paraded across the stand, there seemed to be no escape. Chaloner grew desperate. He refused to enter a plea. He feigned mental illness. Finally, he begged, claiming that to find him guilty would be comparable to murder. Judge and jury were not moved. He was found guilty of treason and sentenced to death by hanging, to be carried out on March 22, 1699. Chaloner spent his final days in prison writing pleading letters to Newton, praying for God to move his heart. He continued to insist that he had been framed, even as he stood at the gallows.
Newton never responded. The recoinage was completed that same year, at great expense but with remarkable efficiency. Newton soon returned to the natural sciences, publishing Opticks, a foundational text on the nature and behavior of light, in 1704. He continued working for the Mint for the rest of his life, free of William Chaloner's trickery.