End of 17th Century Bonanni Type microscope by Nicolas Dufur à Rouen, ca. 1680-90

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 a significant innovation 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 Jesuite 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 the production of microscope lenses. He used his lenses to build his own 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, which could in fact also belong to the retailer or the owner.

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.

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

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.