V.

Newton’s Later Work

A few months before publication of the Principia, Newton emerged as a defender of academic freedom. King James II, who hoped to reestablish Roman Catholicism in England, issued a mandate to Cambridge in February 1687. This mandate called on the university to admit a certain Benedictine monk, Alban Francis, to the degree of Master of Arts without requiring him to take the usual oaths of allegiance to the Crown. The university saw this mandate as a request to grant preferential treatment to a Catholic and as a threat both to tradition and standards, so it steadfastly refused. Newton took a prominent part in defending the university’s position. The university senate appointed a group (including Newton) to appear before a government commission at Westminster, and they successfully defended the university’s rights. After the downfall of James II in the Glorious Revolution of 1688, Newton was elected a representative of the university in the Convention Parliament, in which he sat from January 1689 until its dissolution a year later. While he does not appear to have taken part in debate, Newton continued to be zealous in upholding the privileges of the university.

Newton’s public duties brought a change to his retiring mode of life and required frequent journeys to London, where he met several prominent writers and intellectuals, most notably philosopher John Locke and diarist and civil servant Samuel Pepys. In the early 1690s, possibly in response to the intellectual exertion of writing the Principia, Newton suffered a period of depression. Opinions differ among Newton’s biographers as to the permanence of the effects of the attack.

In the years after his illness, Newton summoned the energy to attack the complex problem of the Moon’s motion. This work involved a correspondence with John Flamsteed, England’s first Astronomer Royal, whose lunar observations Newton needed. However, misunderstandings and quarrels marred their relationship, which ended sourly. In 1698 Newton tried to carry his lunar work further and resumed collaboration with Flamsteed, but difficulties arose again and Newton accused Flamsteed of withholding his observations. The two scientists had not resolved the dispute when Flamsteed died in 1719.

In 1696 Newton’s friends in the government secured a paying political post for him by appointing him warden of the mint. This position required that he live in London, where he resided until his death. Newton’s work at the mint included a complete reform of the coinage. In order to combat counterfeiting, he introduced the minting of coins of standard weight and composition. He also instituted the policy of minting coins with milled edges. Newton successfully carried out these tasks, which demanded great technical and administrative skill, in the three years leading up to November 1699. At that time his peers promoted him to the mastership of the mint. This position was a well-paid post that Newton held for the rest of his life.

In 1701 Newton resigned his chair and fellowship at Cambridge and in 1703 was elected president of the Royal Society, an office to which he was reelected annually thereafter. In 1704, a year after the death of his rival Hooke, he brought out his second great treatise, Opticks, which included his theories of light and color as well as his mathematical discoveries. Unlike the Principia, which was in Latin, Opticks was written in English, but Newton later published a Latin translation. Most of Newton’s work on Opticks was done long before he relocated to London. One of its most interesting features is a series of general speculations added to the second edition (1717) in the form of “Queries,” or questions, which bear witness to his profound insight into physics. Many of his questions foreshadowed modern developments in physics, engineering, and the natural sciences.

In 1705 Queen Anne knighted Newton. By this time Newton was the dominant figure in British and European science. In the last two decades of his life, he prepared the second and third editions of the Principia (1713, 1726) and published second and third editions of Opticks (1717, 1721) as well.

During these last two decades Newton was entangled in a lengthy and bitter controversy with Leibniz over which of the two scientists had invented calculus. This controversy embittered Newton’s last years and harmed relations between the scientific communities in Britain and on the European continent. It also slowed the progress of mathematical science in Britain. Most scholars agree that Newton was the first to invent calculus, although Leibniz was the first to publish his findings. Mathematicians later adopted Leibniz’s mathematical symbols, which have survived to the present day with few changes.