ADRIEN AUZOUT, 1622–91. Astronomer and instrument-maker active in the scientific circles in Paris during the 1660s, he was a frequent correspondent of Huygens on optical matters.
FRANCIS BACON, 1561–1626. Philosopher, statesman, Lord Chancellor of England, First Viscount of St Albans, thus also known as Lord Verulam or Verulamius. Bacon held that science should be based on systematic investigation rather than blind acceptance. He set out these views in works such as Novum Organum and New Atlantis, a utopian novel depicting an ideal scientific community, which served as a template for the later Royal Society.
ISAAC BEECKMAN, 1588–1637. Copiously self-educated Middelburger, sometime candle merchant, Latin teacher and church minister, he corresponded with Snel and Mersenne and befriended Descartes. His later years devoted to mathematics, mechanics and optics make him the successor to Stevin and the forerunner of Christiaan Huygens.
WILLEM BOREEL, 1591–1668. Dutch ambassador to France, 1649–68, he had a lively interest in telescopes.
ISMAËL BOULLIAU, 1605–94. Born in Loudun to Calvinist parents, he converted to Roman Catholicism and became a priest. He moved to Paris, where he pursued many scholarly interests, publishing significant works on astronomy, geometry and the nature of light.
ROBERT BOYLE, 1627–91. Irish natural philosopher, his studies mainly in Oxford established him as the father of modern chemistry. He also investigated the pneumatics of air and the vacuum; Boyle’s law states that pressure is in inverse proportion to volume for a given quantity of gas.
ALEXANDER BRUCE, c.1629–80. Earl of Kincardine and a wealthy Scottish landowner, he collaborated and later quarrelled with Huygens in early attempts to make seagoing pendulum clocks.
SUSANNA CARON, 1652–? Known to Huygens as Suzette, she was a cousin and close friend. She married a French nobleman, François de Civille, becoming Madame de la Ferté.
GIOVANNI DOMENICO CASSINI, 1625–1712. Professor of astronomy at Bologna, he moved to Paris in 1669 to run Louis XIV’s new observatory. He made calculations of the rotational periods of Mars and Jupiter and its four Galilean satellites. Using ever longer and more powerful telescopes, he discovered four moons of Saturn in addition to the first, Titan, discovered by Huygens.
JACOB CATS, 1577–1660. Poet and statesman, grand pensionary of Holland, 1636–51. His often humorous and moralistic verse was more conservative than that of Constantijn Huygens and the Muiden Circle.
MARGARET CAVENDISH, 1623?–73. Writer and philosopher. Of a staunch royalist family, she served at the court of Henrietta Maria, wife of Charles I, but later lived in exile in Paris and Antwerp, where she became interested in scientific questions.
JEAN CHAPELAIN, 1595–1674. Poet, critic, and a founding member of the Académie Française. He turned down prestigious appointments offered by Cardinal Richelieu and other powerful figures, and remained without ambition and loyal to his many friends, including Huygens.
JEAN-BAPTISTE COLBERT, 1619–83. Minister and controller of finance under Louis XIV. Colbertisme demanded the increase of industry, trade and regulation, all directed towards enriching the French state in the person of the king.
SALOMON COSTER, c.1620–59. Huygens’s first clock-maker in The Hague.
PIERRE DE CARCAVI, c.1600–84. French royal librarian and mathematician, friend of Pascal and Fermat.
PIERRE DE FERMAT, 1607–65. Mathematician and lawyer, his analysis of curved lines was a precursor to calculus. He also made advances in number theory and, with Pascal, founded the field of probability. He was not overgenerous in leaving proofs of his theorems.
JACQUES (JACOB) DE GHEYN II, 1565–1629. A Flemish dynasty of painters and engravers, the de Gheyns were neighbours of the Huygenses in The Hague. De Gheyn II found favour with the House of Orange and made an engraving of Prince Maurits aboard Stevin’s sand-yacht.
LEOPOLDO DE’ MEDICI, 1617–75. Born at the Pitti Palace in Florence into the ruling family of the Grand Duchy of Tuscany, he was made cardinal and governor of Siena. Inspired by Galileo, he became an enthusiastic supporter of the sciences and established the Accademia del Cimento.
HENRI LOUIS HABERT DE MONTMOR, c.1600–79. Royal councillor, mathematician and cheerleader for Descartes. The ‘académie Montmor’ that he hosted at his house in Paris from 1657–64 was an informal forerunner of the French Academy of Sciences.
GILLES PERSONNE DE ROBERVAL, 1602–75. Eager to be considered the equal of his colleagues, he made innovations in fields from mathematics to mechanics and optics. He claimed other discoveries and inventions, but was often reluctant to publish, poor at taking criticism and quick to argument.
JOHAN DE WITT, 1625–72. As grand pensionary during much of the Stadholderless Period, 1650–72, he attempted to introduce a more liberal, tolerant and devolved form of government to the Dutch Republic. But following the invasion of the country in 1672, he and his brother Cornelis were lynched by an angry mob.
RENÉ DESCARTES, 1596–1650. Though born in France, he spent most of his working life in the Dutch Republic, where he found the quiet and tolerance he sought to develop his philosophical ideas. His famous Discourse on Method found a Dutch publisher. He was a friend of the elder Constantijn Huygens, with whom he worked on lens development, and became a profound influence on his son Christiaan. It was not always to his advantage that he preferred the power of reason to empirical tests, and while his reputation as a philosopher still stands, he is no longer seriously regarded as a scientist.
JOHN DONNE, 1572–1631. Considered the foremost English metaphysical poet, he was also an Anglican priest, becoming Dean of St Paul’s, and a member of Parliament.
CORNELIS DREBBEL, 1572–1633. An inventor of wild imagination, Drebbel was born in Holland but moved to London, where he was employed at court, putting on masques and presenting an array of miraculous devices, from perpetual-motion machines to the camera obscura. Beneath the showmanship lay a fine understanding of mechanical and optical principles.
NICOLAS FATIO DE DUILLIER, 1664–1753. Swiss-born, he lived mainly in England and Holland, where his facility with the new mathematics brought him into contact with Newton, Leibniz and Huygens. He did not fulfil his early promise, however, and later joined a religious sect.
FREDERIK HENDRIK, Prince Of Orange, Stadholder, 1584–1647. The youngest son of William the Silent, he played a decisive role in the second half of the Eighty Years War. In 1625 he married Amalia van Solms and succeeded to the stadholderate.
GALILEO GALILEI, 1564–1642. A physicist and astronomer of unprecedented range and achievement, he was the giant upon whose shoulders Christiaan Huygens stood. Lamps swinging in Pisa cathedral sparked his investigation of pendulum motion. In 1610 he used a telescope to observe four moons of Jupiter, the first bodies in the solar system that clearly did not orbit the Earth, contradicting both Aristotelian and Church doctrine.
NICOLAAS HARTSOEKER, 1656–1725. Astronomer. Passionate about the sciences from childhood, he gained instruction in microscopy from Leeuwenhoek. In 1684 he settled in Paris, where he built large telescopes at the observatory.
THOMAS HOBBES, 1588–1679. Best known as the author of Leviathan, the philosophical fig leaf for authoritarian governments ever since, he was well travelled and well connected, and his interests were all-encompassing. He was an enthusiastic but incompetent mathematician, and his efforts were derided by Huygens and others. Descartes’s writings excited his interest in optics, but he feared the vacuum was the work of the devil.
SUSANNA HOEFNAGEL, 1561–1633. Constantijn Huygens’s mother came from a wealthy Antwerp trading family. Her brother Joris was renowned as a miniature painter, and other members of the family also made their name as artists.
PIETER CORNELISZOON HOOFT, 1581–1647. Poet, playwright and historian. As magistrate of Muiden, he hosted a famous literary circle at the castle where he resided.
ROBERT HOOKE, 1635–1703. While studying at Oxford, he assisted Boyle, becoming the best experimenter of his day. He made several discoveries, including the law of elasticity that bears his name, but jealously guarded his work, which often led to conflict with his peers and denied him due recognition. His major published work was Micrographia, a magnificently illustrated work on optics.
JOHANNES HUDDE, 1628–1704. He studied law at Leiden, but became more interested in mathematics, Cartesian geometry and probability, about which he corresponded with Spinoza, de Witt and Huygens. Later, as mayor of Amsterdam, he made improvements to the hygiene of the city’s canals.
CHRISTIAAN HUYGENS, 1629–95. Passim.
CHRISTIAEN HUYGENS, 1551–1624. Christiaan’s paternal grandfather. Born in Brabant, he became secretary to William the Silent in 1578, continuing in that position to the council of state appointed after William’s assassination in 1584, thus inaugurating a lineage of Huygens service to the Dutch Republic.
CONSTANTIJN HUYGENS, 1596–1687. Passim, especially chapters 2–4. Christiaan’s father. He married Susanna van Baerle in 1627.
CONSTANTIJN HUYGENS, 1628–97. Christiaan’s older brother. The pair collaborated in lens-grinding and astronomical observation, when his secretarial duties to William III did not take precedence. He married Susanna Rijckaert in 1668. One son.
LODEWIJK HUYGENS, 1631–99. Christiaan’s younger brother and black sheep of the family, he got into trouble for duelling at college and improperly accepted gifts as the magistrate of Gorinchem. He married in 1674. Four sons.
PHILIPS HUYGENS, 1633–57. Christiaan’s youngest brother, he became ill and died in Marienburg (now Malbork in Poland) while on an embassy mission.
SUSANNA HUYGENS, 1637–1725. Christiaan’s sister. Although her accomplishments might perhaps have equalled those of her brothers, her father did not wish his daughter to become an intellectual. She married a cousin, Philips Doublet, in 1660. She had six children, three of whom survived to adulthood.
ZACHARIAS JANSEN, c.1580–c.1630. Middelburg lens-maker, unreliably claimed as the maker of the first telescope.
ANTHONI LEEUWENHOEK, 1632–1723. Work as a draper’s bookkeeper in Amsterdam may have introduced him to lenses. He returned to his hometown of Delft and began making microscopes with tiny bead lenses, through which he was able to observe numerous protozoa for the first time.
GOTTFRIED WILHELM LEIBNIZ, 1646–1716. Employed by a series of electors of Germany, he was able to find time for philosophy and mathematics among routine diplomatic duties. He developed the form of differential and integral calculus employed today, leading him into dispute with Newton, whose method of ‘fluxions’ was devised earlier but not published.
JAN LIEVENS, 1607–74. Hailed as more brilliant than Rembrandt when a young man in Leiden, he travelled widely in search of work, coming under the influence of van Dyck in England, after which his output became more conventional in both subject matter and style.
HANS LIPPERHEY,?–1619. German-born spectacles-maker of Middelburg, he demonstrated his telescope to Prince Maurits at The Hague in 1608.
JOHN LOCKE, 1632–1704. English philosopher and physician regarded as the founder of modern liberalism. His empiricism owed much to Bacon and was opposed to Cartesian a priori reasoning. He spent five years in exile in Holland during the reign of Charles II.
LOUIS XIV, 1638–1715. King of France for all but the first five years of his life, he took steps to increase French military might, centralize power, and embellish the state through the arts.
MARIN MERSENNE, 1588–1648. French theologian, mathematician and music theorist, he was one of the principal scholarly figures of his age, counting Galileo and the elder Constantijn Huygens among his many correspondents.
JACOB METIUS?–1628, and ADRIAAN METIUS, 1571–1635. Sons of an Alkmaar military engineer and cartographer, Jacob was wrongly believed by contemporaries to have invented the telescope. Adriaan was a surveyor and mathematician.
ROBERT MORAY, 1608/9?–73. A Scottish army officer, he served widely in France. Upon the Restoration in 1660, he settled in London and was one of the founding members of the Royal Society.
ISAAC NEWTON, 1642–1727. England’s greatest scientist, he unwove the rainbow, to the dismay of poets from Blake to Keats. His experiments with light, the laws of motion and his theory of gravitation are set out in a 1672 paper, New Theory of Light and Colours, and in Principia Mathematica (1687) and Opticks (1704). His ideas nullified Descartes’s science and laid the scientific foundations for the Enlightenment. A disputatious and unpleasant man, he was a fellow of Trinity College, Cambridge and master of the royal mint.
HENRY [HEINRICH] OLDENBURG, c.1619–77. Born in Bremen, he settled in England in 1653. During his continental travels, he had made the acquaintance of many leading scientists, and subsequently proved an invaluable ‘foreign secretary’ of the Royal Society, promoting an international scientific discourse between sometimes reluctant correspondents.
DENIS PAPIN, 1647–1713. French physicist and inventor, he worked with Huygens, Leibniz and Boyle on experiments with air pressure, and later invented a steam digester, a forerunner of the steam engine.
BLAISE PASCAL, 1623–62. French mathematical prodigy and philosopher of religion, he developed the theory of probability with Fermat. He participated in physical experiments on pressure, and invented a calculating machine, to which Huygens later made modifications.
PIERRE PETIT, 1598–1677. Military engineer and surveyor, he frequently worked with Christiaan Huygens on inventions and made instruments for him in Paris.
REMBRANDT HARMENSZOON VAN RIJN, 1606–69. Painter and print-maker considered by many to be the greatest artist of the Dutch Golden Age. The elder Constantijn Huygens secured early commissions for him, although his style subsequently diverged from courtly tastes.
WILLEBRORD SNEL [SNELLIUS], 1580–1626. He succeeded his father as professor of mathematics at Leiden and independently discovered the law of refraction that bears his name.
BARUCH SPINOZA, 1632–77. Philosopher disowned by his Sephardi Jewish community, his work on ethics, consciousness, God and nature, and biblical truth made him a figurehead of Enlightenment thinking. He made a humble living as a lens-grinder, living near Leiden and in Voorburg, near The Hague, which brought him into contact with the Huygens brothers, who held him in high regard.
SIMON STEVIN, 1548–1620. Born in Bruges, he moved to Leiden, where he made a European reputation as a highly imaginative inventor, while also teaching mathematics and serving as superintendent of finance to Prince Maurits of Orange. He was a prolific writer, producing works – in Dutch, unusually for the period – on everything from bookkeeping to the design of fortifications.
JOHANNES SWAMMERDAM, 1637–80. He studied medicine at Leiden, but was early on captivated by the possibilities of the microscope, discovering red blood corpuscles. His compendious observations of insects laid the foundations of modern entomology.
SUSANNA VAN BAERLE, 1599–1637. Her parents died when she was young, and she inherited a share of her father’s trading fortune. She wrote verse and painted nature-based still lifes, but her work does not survive. She married the elder Constantijn Huygens in 1627 and died following the birth of their fifth child.
JACOB VAN CAMPEN, 1595–1657. Painter and architect of Amsterdam’s city hall (now used as a royal palace) and, with Pieter Post, of the Mauritshuis in The Hague. He had lived in Italy, from where he introduced to the Dutch Republic a severe version of Palladian classicism.
JOOST VAN DEN VONDEL, 1587–1679. Playwright and poet born in Cologne, he became the most important poet and dramatist in the Dutch Republic, writing verses in celebration of the House of Orange and plays reflecting the political and religious disputes of the time.
FRANS VAN SCHOOTEN (THE YOUNGER), 1615–60. Followed his father as professor of mathematics at Leiden. He lived for a time in Paris and met Mersenne and Descartes. He later inducted de Witt, Hudde and Huygens into Cartesian geometry.
ANNA VISSCHER, 1584–1651, and MARIA TESSELSCHADE VISSCHER, 1594–1649. Muses to the poets of the Muiden Circle, the Visscher sisters were highly accomplished in many arts and well able to hold their own in verse.
JOHN WALLIS, 1616–1703. England’s leading mathematician until Newton. Ordained in 1640, he acted as code-breaker for the Parliamentarian side during the Civil War, but later became the king’s chaplain and a founding member of the Royal Society.
WILLEM [WILLIAM] I, PRINCE OF ORANGE, STADHOLDER, 1533–84. He led the Dutch Revolt against Spain in 1568. For his shrewd political judgement and military skill, he earned the sobriquet of William the Silent and, in the Netherlands, the father of the fatherland.
WILLEM [WILLIAM] III, PRINCE OF ORANGE, STADHOLDER, KING OF ENGLAND, SCOTLAND AND IRELAND, 1650–1702. Grandson of Frederik Hendrik, he was appointed as stadholder in the ‘disaster year’ of 1672 and crowned king of England in 1689 by virtue of marriage to his cousin Mary twelve years earlier.