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Bonanni Type microscope signed Nicolas Dufur à Rouen, ca. 1680-1700

Filippo Bonanni (or Buonanni, 1638-1725), a Jesuit scholar from Rome who worked in several scientific and technical fields, described in his book Micrographia Curiosa in 1691 a compound microscope with three lenses. The two types of compound microscopes he designed were significant innovations in the optics and mechanics of the late 17th-century microscope. One of them was intended for observation in transparent samples on slides or opaque surfaces in reflected light, based on a focusing mechanism in which the lens tube was screwed up and down inside the cylindrical body of the microscope in a configuration later called a screw-barrel. Following Bonanni, this configuration soon became the accepted method in one of the most popular single microscope models from the late 17th century and most of the 18th century.

Bonani entered the Jesuit Society in 1654 at the age of 17. In 1656 he was sent to study at the Society's prestigious Roman College as a student of Athanasius Kircher, working on producing microscope lenses. He used his lenses to build his microscope and develop scientific studies on multiple specimens. He also became a skilled engraver.
After Kircher's resignation from the position of professor of mathematics at the Roman College, Bonani was elected to succeed him. After Kircher's death in 1698, Bonani was appointed treasurer of the well-known Wunderkammer collected by Kircher and set up in the Roman College. He published a catalog of the collection entitled Musæum Kicherianum in 1709.

As a believer in the theories of spontaneous generation, he became bitter a critique of Francesco Reddy's experimental work, defending the Aristotelian view. Although he raised important questions - such as whether observers through a microscope saw what they expected rather than what was there, later writers tended to underestimate him.

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From Bonanni 1691

Other early microscope makers in the Italian sphere took this general idea. Giuseppe Campani (1635-1715) from Rome was one of Italy's most prominent optics manufacturers in the late 17th century. Over fifty years of activity, Campani produced many optical instruments with lenses of excellent workmanship. He included Bonanni's design while adding a second threading system of the draw-tube into the objective tube that provides the microscope with various magnifications. He even published it to perform microscopic examinations during medical and surgical activities. The idea was also copied by other manufacturers in the Italian countries and France, such as Pietro Patroni (1676/7-1744) and François De Baillou (ca. 1700-1774), and others. Microscopes of a similar design are also known with the signatures of some French makers.

The microscope seen here is of the same category. It is signed on the outer cylinder collar: NICOLAS DUFUR A ROUEN. This is an unknown name in the onomasticon of early 18th century makers.

A view into the microscope tubes reveals only two biconvex lenses: an eye lens and an objective lens. Thus, this microscope does not have a field lens. Since Johann Wiesel (1583-1662), an optician from Augsburg, already contained a field lens in his microscopes and telescopes in 1654 and other makers such as Campani and Divini were quick to adopt this idea rather rapidly, it may be dated to about 1660 or somewhat later. But due to some stylistic considerations and for the sake of caution, I tend to place it around 1680.


This microscope bears on the tube holder's ring the inscription:


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The family name Dufur (or Dufour) is a French nickname for a baker, derived from "du four", which literally translates to "of the oven". It can also be a habitational name for someone from Le Four, which is the name of several places in various parts of France. However, there is no evidence of a manufacturer of scientific instruments with this name in Rouen or anywhere in France during the 17th or 18th centuries. Therefore, it is more likely that this is the name of the owner. This assumption suggests that the distinct Italian typology of this microscope and its high workmanship can be linked with one of the well-known Italian manufacturers of the late 17th century.

A Harpsichord signed and dated Nicolas Dufour a' Paris 1683 is kept in the National Music Museum of South Dakota in Vermillion (the NMM). This is the only instrument known to be made by Nicolas Dufour. Unfortunately, nothing is known about his life, although it is possible that he was related to Claude Dufour (1628/9-1709), who was a known harpsichord maker in Lyons, and that a harpsichord made by him has also survived. Based on the current information, we cannot determine anything about Nicolas Dufour's career, or how the microscope seen here can be related to him.

Giuseppe Campani’s (1635-1715) compound microscopes designed for medical diagnosis. Special Collections, Stanford University Library

In 1653, a French physician and chemist named Pierre Borel made the first recorded observation of blood under a microscope. He described seeing "animals in the shape of dolphins or whales" swimming in human blood, "as if in a red ocean." Over the next few years, he made other observations of bodily fluids under the microscope, such as the white corpuscles in serum and chyle that are not found in urine, as well as the valves of pores, vessels, and veins. Borel's work in anatomy paved the way for future scientific discoveries using microscopes.

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Around 1620, Cornelis Drebbel, a Dutch inventor, created his own version of a compound microscope using two convex lenses. He polished the lenses finely using a glass-grinding machine that he had invented himself.

During the mid-17th century, the idea of studying the plague under a microscope emerged in Rome. Athanasius Kircher, a German Jesuit polymath who was reading publications by Fontana, Scheiner, and the Lincean group using the microscope, decided to test the instrument during an epidemic. Kircher's book, "Scrutinium Physico-Medicum Contagiosae Luis, Qui Pestis Dicatur" (Physico-Medical Examination of the Contagious Pestilence Called the Plague, Rome, 1658), was the first book to examine the blood of plague victims under a microscope and publish the results. 

Kircher was likely the first person to use a microscope to investigate the causes of diseases. He observed that the blood of plague patients was full of numerous tiny worms that couldn't be seen without a microscope, but could be seen in all decomposing matter under the microscope. He was also the first to explicitly propose the theory that infectious diseases are caused by tiny animals, or animalculae, that can be transmitted from one person to another.


Bendini, S. 2021. Giuseppe Campani, “Inventor Romae,” an Uncommon Genius (Nuncius Series, Volume: 8), Pp. 644–690. The Hauge.

Boalch, D. H. Makers of the Harpsichord and Clavichord 1440-1840. Third edition, edited by Charles Mould (Oxford: Clarendon Press 1995), p. 300.

Borel, P. Historiarum et observationum medico-physicarum Centuria IV (Paris, 1657 ed.; 1653), 198; see Didier Foucault, Pierre Borel médecin et savant castrais du XVIIe siècle: textes choisis, trans. Jean Golfin and Foucault, Cahiers d’histoire du Centre d’étude d’histoire de la medicine de Toulouse, 7 (Toulouse: Pierre-C. Lile, 1999).

Buonanni, F. 1691. Observationes circa Viventia, quae in rebus non Viventibus reperiuntur. Cum Micrographia curiosa. Roma.

Clay, R. & Court, T. 1932. The History of the Microscope. London.

Findlen, P. 2022. Microscopic musings: Athanasius Kircher and the Roman plague of 1656–57. Harvard Library Bulletin,

Kircher, A. 1659. Scrutinium physico-medicum contagiosae luis, quae dicitur pestis. Vorwort von Chr. Lang. Leipzig.

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