Chris Salmon writes:

Back in 1695, England's Royal Mint discovered a serious problem: A massive portion of the circulating currency was phony. As counterfeiting methods grew increasingly clever, the Mint turned to England's brightest mind for a solution. Isaac Newton was appointed Warden of the Mint, a one-man army who waded through London's underbelly to restore the currency's integrity. Most counterfeiters were easy prey for Newton, but William Chaloner, a shadowy kingpin, kept eluding his grasp.

Chaloner had trained as a nail maker's apprentice, but he found a more lucrative application for molten metals: coining 30,000 guineas. The counterfeiter's self-made wealth enabled him to pose as a gentleman and gave him an ego to match his intellect.

Newton wanted nothing more than to destroy Chaloner, and the feeling was mutual. Chaloner appeared before a parliamentary committee, where he insinuated that Newton was incompetent and blamed Mint employees for the epidemic of phony coins. Enraged, Newton intensified his efforts.

When Chaloner set up a coining facility in Egham, 20 miles outside of London, Newton sensed an opening. He began studying Chaloner's sophisticated casting method-which involved pouring molten metal into brass molds before filing down the molds' faces, resulting in much sharper images on the phony coins.

By September 1697, Newton had enough evidence to lock Chaloner up-but not for long. Working through intermediaries inside the prison and out, Chaloner bribed the prosecution's star witness into fleeing to Scotland. Chaloner was released and accused Newton of framing an innocent man.

This attack on Newton's integrity was the last straw. If Chaloner was going to play dirty, then so was Newton. Acting more the grizzled sheriff than an esteemed scientist, Newton bribed crooks for information. He started making threats. He leaned on the wives and mistresses of Chaloner's crooked associates. In short, he became the Dirty Harry of 17th-century London.

After nearly two more years of relentless pursuit, Newton's extreme measures had gathered enough evidence to put Chaloner away for good. This time, the charges stuck. On March 3, 1699, the counterfeiter was found guilty of high treason. The next day he was sentenced to hang.

To read the complete article, see:Isaac Newton: 17th-Century London's Dirty Harry(www.mentalfloss.com/blogs/archives/150769)