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During his apprenticeship, however, Antoni would not have had much time to enjoy the pleasures of Amsterdam. The responsibility of a master to his apprentice was to prepare the boy for both the world of trade and the wider world outside. It was not thought that one could achieve these ends without hard work—and long hours—six days a week. The apprentice was expected, during these years, to respect and obey his master, as much as he would his own father. Usually the boy lived with his master’s family, who would be responsible for feeding and clothing him, but since it appears that Antoni lived with his uncle, this would have been his uncle’s responsibility.
Davidson had a great deal to teach Antoni. An apprentice to a draper would learn about the technologies involved in making the different kinds of cloth—combing, spinning, weaving, bleaching—in order to better negotiate with the cloth makers and with his customers. Those in the cloth trade had much to keep up with; unlike cloth industries in other countries, and unlike some other industries in the Dutch Republic, the Dutch cloth industries eagerly adopted new technologies as soon as they were developed, such as the filling mill, the twining mill, hot presses, and the ribbon frame. For instance, the “Dutch loom,” invented in 1604, was put into use in Holland almost immediately, but—though it was known in London in 1614—was not adopted by Lancashire weavers until the beginning of the eighteenth century. The draper’s apprentice would learn about the market for the different types of cloth not only in Amsterdam but around the world as well; he would need to understand the global aspects of the cloth trade. He also had to acquire the basics about running his own shop: deciding how much of what stock to order, details about pricing, bookkeeping, taxes, and, if he was hoping to one day become a master in the guild himself, taking on and training apprentices. When he was advanced in his apprenticeship—around the time he was given the proxy power for Davidson—Antoni may have been brought to the Drapers’ Guild House on the Staalstraat to observe a meeting of the cloth-weaving inspectors, such as that which would be later depicted in Rembrandt’s Syndics of the Amsterdam Drapers’ Guild (1662). Antoni could aspire, one day, to be appointed a syndic of the drapers’ guild in Delft.
There was another skill Davidson had to teach his young apprentice, one that would not only alter Antoni’s life but transform science: examining objects through a convex lens. A magnifying glass was a crucial instrument for cloth merchants. It provided the only way to distinguish the thread count—and thus the quality—of fabrics. This was most likely the first time Antoni had ever used a lens—the first time he would have marveled at the fact that a piece of glass could allow him to see what could not be seen with the naked eye.
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Although a young man like Antoni would not have had much call to use lenses before his work in the cloth trade, they were not rare in the Dutch Republic and elsewhere in Europe at this time. Magnifying lenses, also known as burning glasses—because they concentrate the sun’s rays enough to cause combustion—already had a long history. These lenses were convex, that is, bulging out at the center, and thinner at the ends, like a lentil. The oldest known convex lens is the “Nimrud lens,” which dates back to ancient Assyria three thousand years ago and was unearthed in the nineteenth century. When it was found, the Scottish physicist David Brewster proposed that it might have been used either as a magnifying glass, perhaps to help artisans with their engravings, or as a burning glass to start fires. Aristophanes, in his play The Clouds (fifth century BCE), mentions a burning glass used for the latter purpose. Precious stones ground into lenslike shapes may have been used occasionally in ancient times as magnifiers or even as visual aids to help a person with defective sight see better; Nero was said to have observed gladiator games through an emerald. “Reading stones” came into use sometime between the eleventh and the thirteenth centuries; made by cutting a glass sphere in half, they were laid directly on the paper to enlarge the words and images. Such stones were probably used by monks to help them create their illuminated manuscripts.
But it was not until the last few decades of the thirteenth century that convex lenses were fitted into metal frames specifically to assist people with defective vision. The first convex spectacles were used to help older people read more easily. As one ages, the eyes suffer from presbyopia, the progressive loss of power of the eye to focus on nearby objects. The normal human eye is able to see distant objects sharply in its relaxed state. However, for clearly viewing objects nearer than about twenty meters away, the refractive power of the optical system of the eye must be increased; this occurs by the contraction of tiny muscles (called cilia) around the lens of the eye. By increasing the curvature of the lens, the contraction of the cilia results in greater refractive power. At ten years old, the normal eye can adjust or “accommodate” itself to see objects as near as three inches from the eye in sharp focus. This ability decreases with age; by the middle forties the eye can only accommodate itself to see clearly about ten inches removed from the eye. When the abilty to accommodate decreases to about twenty inches away, reading becomes impossible without optical aids. (A person born without this ability in the first place has defective vision that must be corrected sooner, which is why some of us need reading glasses before middle age.)
Up until the nineteenth century, purchasing spectacles for correcting presbyopia was simply a matter of going to a spectacle shop; there were rules of thumb relating the strength of reading glasses to a person’s age, and by trial and error you would find the strength correct for you. The weakest ones generally had focal lengths (that is, the distance over which rays are brought to converge on a single point) about thirty to fifty centimeters (twelve to twenty inches). A shorter focal length has greater optical power. The strength of a lens, expressed in diopters, is the inverse of the focal length in meters; so the strength of these lenses was two to three diopters. Stronger spectacles were available for older people or those who had had cataract surgery (an early version of cataract surgery was already being performed around 800 BCE). Weaker lenses were not common. At the time there was no real demand for weaker glasses—people needing less correction can still read without spectacles, but may suffer eyestrain over time—and weaker lenses were more difficult to grind.
It was only later that lenses could be consistently ground to correct another vision deficit, myopia, or nearsightedness, a problem with seeing distant objects clearly. Correcting myopia requires concave lenses, those that are thickest at the ends and thinner in the middle; they are more difficult to grind than convex lenses. Concave lenses were available for sale in Florence by 1451, and soon spread to other cities in Europe. By the mid-fifteenth century, spectacles were widely prevalent among the elites, not only as aids to vision but as appropriate gifts of courtly patronage, even as status symbols.*3
Once both convex and concave lenses were commonly available, it was only a matter of time before an optical device like the telescope would be invented. Already by Aristotle’s time in the fourth century BCE it was known that a tube could help one view distant objects. In his book On the Generation of Animals, Aristotle explained that “the man who shades his eye with his hand or looks through a tube will not distinguish any more or any less the differences in colors, but he will see further.” In the sixteenth century, the Danish astronomer Tycho Brahe observed the heavens using a long tube; even without lenses, this device enabled Brahe to make the impressively accurate observations of Mars’s orbit that enabled Kepler to discover that the planetary orbits are elliptical, not circular.
By about 1600, the strongest concave lenses in a spectacle maker’s shop had focal lengths of about twenty to thirty centimeters (eight to twelve inches); so the strength of these lenses ranged from three to five diopters. By putting together at two ends of a tube the weakest convex lens with the strongest concave lens then readily available, a telescope approaching useful magnification (about 2 or 2.5 times) could have been created. Only by about 1600, then, was it possible to construct a weak telesc
ope from lenses that were easy to find.
So both the idea behind a tubelike optical device, and the technology to make one with lenses, were in the air around Europe by 1600. But it is not clear who the first person was to put together a tube with lenses to create a working device. It is probable that one of three men from the Dutch Republic was the original inventor of a usable telescope. Isaac Beeckman, a rector of the Latin School in Dordrecht and a friend of Descartes’s, took lens-grinding lessons in the 1630s in Middelburg with Johannes Sachariassen, the son of a spectacle maker named Sacharias Janssen. Sachariassen told Beeckman that the first telescope in the Netherlands had been made by his father in 1604, after a model made by an Italian in 1590. His son’s story is plausible, because at that time Middelburg was the site of a major glass factory established in 1581; it employed a number of Italians, who had deserted from the Spanish army, in which they had fought as mercenaries. Around the time Janssen supposedly made his first telescope, the Middelburg glass factory was run by an Italian named Antonio Miotto. It could well be that an Italian prototype of a telescope made its way to Middelburg, and then to Janssen, who improved it.
Beyond that, the historical record is murky. We know that on September 25, 1608, a “spectacle maker from Middleburg” applied to the States General for a patent on his invention of a new instrument to see objects far away, and requested the opportunity to demonstrate the device to the stadtholder, Prince Maurits, at The Hague. The record of this event does not reveal the name of the spectacle maker. Whoever he was, we know that he showed the prince a device made from two glass lenses, one convex and one concave, enclosed in a tube twelve to fourteen inches long; the concave lens was used for the eyepiece, and the convex for the objective (the lens farthest from the eye). From the tower of the prince’s home in The Hague, the men were able to see the clock on the Town Hall in Delft, almost six miles away! On this day the prince was entertaining Ambrogio Spinola, the commander of the Spanish troops in the Netherlands, who was at The Hague negotiating for peace. Seeing no reason to dismiss his onetime foe, Maurits allowed Spinola to remain and observe the demonstration. Spinola is said to have remarked to Maurits’s son, Prince Frederik Hendrik, “From now on I can no longer be safe, for you will see me from afar.” Prince Frederik Hendrik jokingly assured Spinola that he would not allow his men to fire upon him, even though they would see him before he would see them.
Who was this “spectacle maker from Middelburg”? It might have been Janssen, though it is odd that he waited four years from when he supposedly improved the Italian prototype to request permission to demonstrate it to Prince Maurits. It may have been another spectacle maker from Middelburg, Hans Lippershey. A week after the demonstration to Prince Maurits, Lippershey submitted a patent application for a different kind of telescope altogether: one that had two viewing lenses, like binoculars, and with lenses made of quartz, rather than glass. Before two more weeks had passed, a third Dutchman, Jacob Metius of Alkmaar, petitioned the authorities for an exclusive patent for an optical device for seeing faraway objects; in his application he acknowledged the efforts of “a spectacle maker of Middelburg” who had preceded him in applying for a patent, but claimed he had been working for two years on his invention and was privy to “secret knowledge” about glass.
Wisely, the States General declined to give anyone a patent for the device, claiming that it was not really new—after all, how innovative could the device be if three supposed inventors had all applied for patents at the same time? Indeed, by this time a Dutch peddler had been reportedly hawking a telescope at the Frankfurt fair. The States General instead awarded Lippershey nine hundred guilders for making three binocular instruments in five months, and Metius was granted some money to improve his prototype. Janssen seems not to have received anything. One wonders whether that is why he later became involved in two counterfeiting schemes, one in 1608, and one in 1620, around the time that Johannes Vermeer’s family was implicated in a similar plot. In order to avoid execution for the second offense, Janssen had to leave Middelburg—in fact, he completely vanished from the historical record at that time.
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Once introduced in the Dutch Republic, the new optical instrument spread quickly throughout Europe. Not surprisingly, after Spinola had witnessed the demonstration of the new device with Prince Maurits, he obtained a telescope of his own in short order and showed it to the ruler of the Spanish Netherlands, Archduke Albert of Austria—who had acquired two for himself by the spring of 1609. The papal nuncio Guido Bentivoglio, a former student of Galileo’s, saw the Archduke’s instruments and described them in a letter to Cardinal Scipione Borghese, a nephew of Pope Paul V. In mid-April 1609 the English ambassador to the Spanish Netherlands suddenly took up astronomy with enthusiasm while at the archduke’s castle, suggesting that he, too, was using the new device. By then the instruments were commercially available at a shop on the Pont Neuf in Paris, by May they could be purchased in Milan, and by summer in Bavaria, London, Rome, Naples, Venice, and Padua. In 1617 Galileo’s intimate friend Giovanfrancesco Sagredo was disappointed to discover that his correspondents in distant India already had plenty of telescopes and were therefore not impressed by the ones he sent them.
Sometime during this period, a device fell into the hands of Galileo. He was not, as is often claimed, the telescope’s inventor. Nor was he the first to turn the instrument to the heavens; others—such as Thomas Harriot and William Lower in England—used telescopes to view the moon a few months before Galileo. However, Galileo was one of the first to improve the device so that it could be fruitfully applied to astronomy. He swiftly understood that, with lenses purchased in shops, it was only possible to create devices with a magnification of three times. He realized that greater magnification would require lenses with increased differentiation in power between the convex objective and the concave eyepiece. This meant he would need to grind and polish his own lenses. He began to do so and, in August of 1609, presented a device that magnified nine times to the Venetian senate, which was impressed enough that it doubled his salary at Padua and gave him a permanent appointment there. But Galileo continued working on his grinding and polishing techniques, and by the beginning of 1610 he had made telescopes that magnified twenty and even thirty times. More importantly, he adapted the device for astronomical use by adding aperture stops to his objective lenses. In this way Galileo limited the amount of light entering the lens, reducing the interference caused by the brightness of celestial bodies; this made it possible to accurately observe stars and other bright bodies.
Nor was Galileo the first to use the word “telescope,” as some believe, though he was present at the term’s birth. Galileo had been calling his device a perspicillum (the English were calling it a “perspective cylinder”). On April 14, 1611, he attended a dinner held at the Accademia dei Lincei, the scientific organization founded by Federico Cesi in Rome in 1603. Cesi had been inspired to form the scientific society by Giambattista Della Porta’s description of the natural philosopher as an investigator “examining with lynx-like eyes those things which manifest themselves.” After a lavish banquet, the party repaired outside to use one of Galileo’s telescopes to observe Jupiter’s moons and Saturn’s “companions” (not yet recognized as rings). At the dinner the Greek poet and theologian John Demisiani had baptized the instrument telescopio, from the Greek for “to see at a distance.”
Once the telescope was in use, it was not long before another, related device was invented: the microscope. Galileo may have been the first to use a telescope to view objects close up, thus setting the stage for the invention of the new instrument. A student of his reported that in 1610 Galileo had used an inverted telescope to observe “a certain insect in which each eye is covered with a rather thick membrane, which is perforated with seven holes like the visor of a warrior to allow it sight.” Five years later Giovanni du Pont described how Galileo had used the device to discover that flies could walk upside down on glass because they were
“inserting the points of their nails in the pores of the glass.” By sometime between 1620 and 1624 Galileo was constructing a special kind of microscope that he called an occhialino, or little eye, for the purpose of, as he put it, “observing minute objects closely.”
Around the same time Galileo made his first microscopes, the eccentric Dutch inventor, instrument maker, and engineer Cornelis Drebbel—then living in London—was also constructing and selling his own microscopes. Drebbel, another artist–natural philosopher, had studied engraving with the famed engraver Hendrick Goltzius in Haarlem; he later married Goltzius’s sister Sophia and moved to England. He was a light-haired, somewhat coarse-looking man with good manners and a brilliant intellect. Constantijn Huygens, who spent much time with him while on his diplomatic mission with the Prince of Orange in London, recalled that “in appearance he is a Dutch farmer, but his learned talk is reminiscent of the sages of Samos and Sicily.” Their relationship was warm; Constantijn remarked to his parents that he had “possessed Drebbel for a whole year, and he possessed me too, his possessor, and a not unfavorable one, unless I mistake me; this he proved to me during many lessons, being more affectionate to me than to any of his friends.” (His parents promptly warned Constantijn not to spend too much time with this “magician.”)
Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing Page 7