In the fall of 1662 Hooke was appointed to his position at the Royal Society, one of whose original founders was his Oxford mentor Wilkins. His duties were “to furnish [the group] every day when they met, with three or four considerable Experiments,” and to undertake any tasks suggested by the fellows; it was thought, too, that he would be able to design ingenious displays that would entice the king to support the society. Because Hooke was charged each week by the society to furnish them with experiments based on their interests at the moment, he was forced to turn his attention to an incredibly wide array of topics, including carriages, fountains, pendulum clocks, respiration, combustion, magnetism, gravitation, telegraphy, astronomy, and music. He made improvements to diving bells, discovered a star in Orion, and inferred the rotation of Jupiter. He developed a way to apply the conical pendulum to watches and invented a machine for cutting gear wheels.
Hooke was not a pleasant fellow. Thomas Molyneux called him “the most ill-natured, conceited man in the world, hated and despised by most of the Royal Society, pretending to have [made] all other inventions, when once discovered by their authors to the world.” Christiaan Huygens told his father, “I know [Hooke] very well. He understands no geometry at all. He makes himself ridiculous by his boasting.” Hooke believed that others were constantly stealing his ideas and inventions. He engaged in vicious disputes with Christiaan Huygens over who invented the conical spring watch mechanism, and with Isaac Newton over, well, most of Newton’s discoveries. When Newton published his “Discourse on Colour” in 1675, Hooke complained that this work was based on experimental results he had published ten years earlier; Newton was forced to admit that he had been “inspired” by Hooke’s research—famously commenting, “If I have seen further it is by standing on the shoulders of giants.” (Since Hooke was a very short man, this was a backhanded insult to him.) Yet later, in 1687, when Newton published his landmark work, the Principia mathematica, he included no acknowledgment of the prior work of Hooke. There is some truth to Hooke’s feeling that others were being fêted for his discoveries. However, in 1665 he published a book that brought him undeniable international acclaim.
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In 1663 the Royal Society charged Hooke with making detailed observations with a microscope of his own design. From the time of its invention until this point, the microscope had been deployed in several studies of insects, such as those by Cesi, Stelluti, and Fontana, who had joined forces in their groundbreaking study of the bee in 1625, and Odierna’s momentous study of the eye of the fly, which appeared in 1644. In 1656 Pierre Borel had published a miscellany of microscopical observations, describing his use of the device to investigate plants, animals, human materials, and minerals. He saw the compound eyes of insects, the beating heart of a spider, the flow of blood in a louse. He observed the texture of the human heart, liver, kidney, and testicles. Borel’s somewhat random collection of observations pointed the way to the potentially limitless possibilities for the deployment of the microscope, including, for the first time, the application of the microscope to studies of the human body. It is not clear to what extent works of Odierna and Borel were read by other natural philosophers of the day; few references are made to their books in the works written in this time. But the publication of Hooke’s microscopical studies was about to give new impetus to the use of the device.
On March 25 Hooke was “solicited”—that is, instructed—by the Royal Society to conduct microscopical observations and demonstrate them to the fellows. (He had previously presented to them some microscopical observations of snowflakes and crystals of frozen urine.) A week later he was charged more specifically with bringing in at least one microscopical observation to every one of the weekly meetings. On April 8 he “delighted” the fellows by showing them common moss under the microscope. The following week he brought in thin slices of cork, cut in both transverse and perpendicular slices. The fellows observed that viewed under the microscope the cork was made up of empty spaces surrounded by walls. Hooke later recalled,
I with … [a] sharp Penknife, cut off from the former smooth surface an exceeding thin piece of it, and placing it on a black object Plate, because it was it self a white body, and casting the light on it with a deep plano-convex Glass, I could exceeding plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular.…
He next cut a piece at right angles from the first piece, discovering that the pores “were not very deep, but consisted of a great many little Boxes, separated out of one continued long pore, by certain Diaphragms.” No one had ever seen these spaces before, or imagined them to exist. Hooke called these box-like pores “cells” because of their resemblance to monks’ chambers. By his careful sectioning of the cork, he had discovered and named cells, the building blocks of all life.
Over the following five months, a cornucopia of fascinating sights met the eyes of the fellows of the Royal Society at their weekly meetings. With his microscope, Hooke gave them entrée into parts of the world not visible to naked sight—parts seemingly chosen at random, whatever took Hooke’s fancy and was readily at hand: the small eels in vinegar, the bluish mold on leather, a spider with six eyes, female and male gnats, the head of an ant, the point of a needle, pores in petrified wood, leaves of sage. Fabrics were of special interest to Hooke: taffeta ribbon, fine cotton lawn, silk from Virginia. He showed them the gilt edge of Venetian paper, the edge of a razor, a millipede, honeycomb seaweed, the tail of a snail, the scales of fish. The demonstrations went on until the end of September. In July, Hooke demonstrated the most impressive of these observations to Charles II himself, presenting the royal patron of the society with a handsome keepsake volume. Once the demonstrations were finished, they were compiled into a book for publication. Hooke’s Micrographia appeared at the start of 1665.
The publication of this work was a scientific and literary event. After seeing it being prepared at his favorite book bindery, Samuel Pepys ordered a copy on the spot. The day he collected it, he stayed up until two in the morning reading, and declared it “the most ingenious book that I ever read in my life.” Pepys was right to be excited. Micrographia was the first full-length monograph devoted (almost) entirely to observations made with a microscope. Of the sixty observations detailed in the book, five were of man-made objects (different fabrics, a razor blade), five of minerals (sand, ice crystals), fifteen of vegetable objects (cork, seaweed) and twenty-seven of animal subjects (mainly insects). (Eight of the observations were nonmicroscopic, having to do with light, the stars, and the moon.) The book was only the second to be published with the imprint (and therefore the imprimatur) of the Royal Society. As befits a Royal Society publication, Hooke laid out in his preface the Baconian motivation for his investigations.
The Rules YOU have prescrib’d YOUR selves in YOUR Philosophical Progress do seem the best that have ever yet been practis’d. And particularly that of avoiding Dogmatizing, and the espousal of any Hypothesis not sufficiently grounded and confirm’d by Experiments.
Like Bacon, Hooke wanted to discover the hidden natures and structures of things, and recognized that instruments were needed to see what could not be seen with the naked eye. Hooke explained that one way to correct for the weakness of the senses was by
a supplying of their infirmities with Instruments, and, as it were, the adding of artificial Organs to the natural.… By the means of Telescopes, there is nothing so far distant but may be represented to our view; and by the help of Microscopes, there is nothing so small, as to escape our inquiry; hence there is a new visible World discovered to the understanding.
Indeed, one of the reasons for writing the book, Hooke told his audience, was to promote the use of instruments, especially the microscope, in science. By the help of the microscope, he urged, “the subtilty of the composition of Bodies, the structure of their parts, the various texture of their matter, the instruments and manner of their inward motions, and all the other possible appearan
ces of things, may come to be more fully discovered.”
The book’s impact on both the scientific community and the general literate public was magnified by its numerous illustrations, including a flea so large it required a foldout page to contain it—as big as a cat, even Christiaan Huygens noted admiringly. Hooke’s friend Christopher Wren may have assisted him with the engravings, but they were all based on the original drawings made by Hooke himself. In these drawings one can see the talented former student of Lely at work.
In all, there were thirty-eight pages of copperplate engravings, which laid out for all to see the incredible intricacy of even the tiniest parts of things that were visible with the new instrument. This was in marked contrast to the “small and indifferent” illustrations in the earlier books of Odierna and Borel. Anyone paging through Hooke’s book could see for himself or herself the delicacy of details opened up to our vision by this instrument. Pictures demonstrated to everyone, as no verbal description could, the beauty and complexity bestowed by God upon even his smallest and most lowly creatures—and, especially, the way the microscope gave access to this unseen world.
In his book Hooke also showed how natural philosophers could learn about vision by microscopical investigations. Micrographia’s figure 8 depicted the compound eye of the drone fly. Hooke explained that he first examined the exterior of the eye, observing that it is composed of some fourteen thousand hemispheres, each perfectly smooth and distributed in a regular fashion over the surface of the eye. Because the hemispheres face all angles, the fly has an incredibly wide field of vision. Hooke next described what he found upon dissecting the eye: an outer, transparent layer, or cornea, filled with a clear liquid and a mucous lining, or retina. He noted that this structure was analogous to the eye of a vertebrate and speculated how the multiple hemispheres could work together to form a precise image of an object and to help the fly determine the position and distance of the object. He concluded his examination by marveling at the mechanism that allowed such a tiny structure to have vision: “How exceeding curious and subtile must the components parts of the medium that conveys light be, when we find the instrument made for its reception or refraction to be so exceedingly small?” With his greatly enlarged image of the fly’s eye, Hooke brought home to his many readers the intricacy of the tiniest structures devised for sight.
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When Leeuwenhoek was in England, examining the chalky soil around Gravesend, Hooke’s book was circulating through the country—a second edition had been printed in 1667—and abroad. During this period books were moving around the continent of Europe, and even across seas, with a speed and efficiency we associate with Internet shopping today. The Royal Society’s Philosophical Transactions, which would soon become the main publishing outlet for Leeuwenhoek’s discoveries, was available on the Continent almost immediately after it was printed in London. Language was a barrier, but not as much as we might think. Some scientific men complained that Micrographia was written in English, rather than the shared scientific language of Latin. Spinoza, for instance, was annoyed by this. But other Dutch speakers were familiar with the book and its contents. Swammerdam seemed to know much about the book—its text as well as its plates—though there is no other evidence that he knew English. Christiaan Huygens translated parts of Micrographia into Dutch for the mathematician, natural philosopher, and bureaucrat Johan Hudde, who deeply admired the book; it is possible that other natural philosophers in the Dutch Republic saw this translation as well.
The book was well known in Rotterdam, where English was common among the residents. In the major cities and commercial centers in the Dutch Republic, English was recognized as a valuable, even necessary, second language. The demand for private tutors of English was high. Constantijn Huygens, for example, had learned English as a boy from his Scottish tutor, George Englisham, and had insisted that his sons learn English as well. Many English and Scots travelers to the Dutch Republic could manage to get by without knowing Dutch, because so many of the locals spoke English. A fair number of locals spoke French as well. The French philosopher Pierre Bayle managed to live in Rotterdam for twenty-five years without learning a word of Dutch. Travelers marveled at the linguistic ability of the Dutch; in 1592 Fynes Moryson remarked that “many of them speake the English, Italyan, and other languages.”
Leeuwenhoek would later frequently deny that he had any familiarity with Hooke’s book when he began his own microscopic examinations. He stressed, time and time again, that he could not have read the book, because he lacked any language but Dutch. However, in this instance it seems that the microscopist doth protest too much. We know his wife Barbara most likely spoke English growing up with her parents, who had, at the time of her birth, recently returned from living in Norwich (where her father had been born). We know that Leeuwenhoek apprenticed for six years to a Scotsman and even had the equivalent of power of attorney for his business activities, some of which would certainly have been conducted in English. So it is probable that Leeuwenhoek could at least read some English. He would later comment in a letter discussing the eyes of the beetle on the “absurdity” of the “English expression, ‘blind as a beetle’”—an indication that he even knew some colloquial English.
Later in his career Leeuwenhoek told his correspondents in the Royal Society that he was reading the issues of the Philosophical Transactions with the use of a Dutch-English dictionary. This was probably Henry Hexham’s English–Dutch and Dutch–English dictionary, either the 1648 first edition or the 1658 second edition. In both, subjects of English grammar are discussed in the Dutch–English volume, and subjects of Dutch grammar in the other. Leeuwenhoek also revealed that he often sought out people who could translate parts of publications for him. In 1675 he remarked that he had plenty of acquaintances who could translate Latin or French for him, but not English, at least not since the death “of a certain gentleman who was proficient in that language,” suggesting that, until then, this gentleman had translated English books and papers for Leeuwenhoek. (He would soon ask for translation help from Alexander Petrie, the pastor of the English congregation in Delft, who wrote an affidavit for the Royal Society attesting to his observations with Leeuwenhoek’s microscope.) In one letter Leeuwenhoek quoted passages from a work by the Royal Society member Richard Waller in Dutch—so either Leeuwenhoek himself or someone else had translated them from English. Even if Leeuwenhoek could not read Micrographia himself, he could easily have had someone translate it, in whole or in part. He would have heard of the book, in Delft and, especially, when he was visiting England. Surely he would have wanted to see for himself what all the fuss what about.
Leeuwenhoek, who had worked so recently as a haberdasher and cloth salesman, would have been drawn to Hooke’s detailed discussion and drawings of what he saw when he observed different fabrics with his microscope. In Micrographia, Hooke explained that the microscopist must begin with the simple; and he accordingly started his observations with the point of a sharp needle and the edge of a razor. He turned next to fabrics: “fine Lawn, or Linnen Cloth,” “fine waled Silk, or Taffety,” and “watered Silk, or Stuffs.” Hooke described how threads of linen appeared under the microscope:
A piece of the finest Lawn [linen cloth] I was able to get, so curious that the threads were scarce discernable by the naked eye, and yet through an ordinary Microscope you may perceive what a goodly piece of coarse Matting it is; what proportionable cords each of its threads are, being not unlike, both in shape and size, the bigger and coarser kind of single Rope-yarn, wherewith they usually make Cables.
The sight of colored silk ribbon astounded Hooke; he observed reflections so lovely and bright that they seemed to come from a cache of precious stones. Hooke elucidated why the watered silk cloth has the strange, but lovely, effect of an “irregular variety of brighter and darker parts.” With a microscope one “may very easily perceive, that it proceeds onely from the variety of the Reflections of light, which is caused by the various Shape
of the Particles, or little protuberant parts of the thread that compose the surface.” Hooke described the way the threads of the woof are bent around the threads of the warping. He included an illustration of the weave. Like Leeuwenhoek, Hooke seemed to have a special interest in fabrics. (He may have designed a fabric pattern and attempted to add gold leaf to a shift already printed with a floral design.) Leeuwenhoek would surely have been interested in Hooke’s microscopic examination of the very same fabrics he himself had examined years before with a magnifying lens.
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There is another discussion in Hooke’s Micrographia that would have excited Leeuwenhoek’s interest. In his preface, Hooke treated his methods for constructing microscopes, and explained why he used a double, or compound, microscope—a microscope with two lenses—rather than a single lens—the kind that Leeuwenhoek was employing.
Hooke described how he made the type of microscope he most often employed. First he took a tube of brass in which he placed at one end a “good plano convex Object Glass, with the convex side towards the Object.” Into the other end he placed a “pretty large plano Convex glass, with the convex side toward my eye.” He would fill the space between the two lenses with water, which helped increase the brightness of the object viewed. He fixed the microscope and the object to a pedestal, allowing for hands-free observing. Although he had made trials with other types of microscopes, he said, he had had more success with this kind of instrument.
Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing Page 23