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Scarlett screw-barrel microscope, ~1720


This instrument is a very rare survivor of an early design for a pocket microscope, which held sway for over a century. It is defined as the Wilson screw-barrel type microscope. It was most likely made c1720 by Edward Scarlett (c1677–1743) in his shop the Archimedes and Globe on Dean Street, near St. Anne's Church, Soho, London. Scarlett (along with Edmund Culpeper) was one of the first opticians to make and sell screw-barrel microscopes shortly after James Wilson introduced it to the Royal Society in 1702. Few of his instruments remain today.

Being a single lens modification of the 17th-century Italian compound microscopes devised by Carlo Antonio Tortoni (1640-1700), Giuseppe Campani (1635–1715), and Filippo Bonanni (1638–1723), the single-lens form is believed to be invented before 1694 by the Dutch mathematician Nicolaas Hartsoeker (1656–1725). This common belief, copied from one historian of science to another, is based on Hartsoeker's description of a simple microscope that used Campani's screw-barrel focusing mechanism and Bonanni's spring stage (see: Giordano Collection: 2009.9.4 for a wooden version and Clay & Court 1932:  43, Fig. 20, for an ivory one). The microscope is essentially a simple magnifier with a threaded attachment that allows focusing by adjusting the distance of the sample to the objective.

It must be stressed though that contra this common belief, Hartsoeker never claimed this microscope to be of his invention. In his Essay de Dioptrique, Hartsoeker (1694: 174) merely wrote as follows: "After talking about the spectacles, I still have to talk about microscopes. The best is with a single glass, from two or three lines up to the tenth part of a line of focus, which is used conveniently with the help of a mechanism of which here is the description. AB is a type of frame to put the eye on it if to prevent the side rays from entering. P is a container where the lens is placed between two silver blades, and which goes to screw the frame AB. OC, QD are two pillars that hold both CD, OQ rings..." (English translation is mine, Y.G.). He then goes on to describe the operation mode of this instrument with some criticism, but the text neither refers to the inventor of this form nor to its producer. Technically, the "original" screw-barrel microscope could have been invented in Italy, the Dutch Republic, France, or the German Lands, and the few existing examples could be made elsewhere. Undoubtedly, when Hartsoeker described it in 1694 it was already an extant form, which may have been circulating around him for enough time to be tested on many occasions as described further on. He even complains that "These microscopes are so inconvenient, that only a very small part of an object is seen by the eye, and so on, it is only possible to illuminate it from behind. These microscopes can scarcely become customary for extremely small objects, such as insects that are seen swimming in stagnant water in the form of animalcules" (ibid: 176, my translation, Y.G.). 

In 1702 James Wilson (c.1665–1730), an English instrument maker, presented in the Philosophical Transactions of the Royal Society an improved pattern of his make. Here, the screw-barrel microscope was in fact part of a two-instrument set, together with an early form of the compass microscope (see Microscope-Antiques.com for more details). By adding a handle that made the microscope more convenient and by simplifying the condensing lens system, Wilson (1702) made the production and use of this instrument easier. In their seminal book, Clay & Court (1932: 44-50) survey in detail the development of Wilson's screw-barrel microscopes, of which only a few signed examples (bearing the incised letters IW) are known. Several more unsigned examples are safely attributed to him (below). This form was also produced and further developed also by Edmund Culpeper (1660–1738), Edward Scarlett (c.1677–1743), and others, well into the last quarter of the 18th century.

There seems to be much confusion regarding the dating of Wilson's instruments as well as his compatriots', most likely resulting from some lack of background in historical and/or archaeological dating principles such as terminus post/ante quem, typological, contextual, and frequency seriation, the meaning of "directing fossils" and so forth. No doubt, Clay & Court's book, and the earlier sources that they quote, most of which are British, reflect very well the typical Victorian to early 20th century approaches of unilinear evolutionary and diffusionist views towards the history of technology, typical of the period's culture-history trend in anthropology, best represented by the archaeologist V. Gordon Childe (1892–1957) and his theories about the advent of technology. Also typical of this era and as late as the 1980s is the anglocentric nature of historiography regarding the history of scientific instruments. Thus, as much as the date of 1694 can be merely seen as terminus ante quem for the introduction of the form (and presumably a very late one), the year 1702 is the terminus ante quem to its first production by Wilson, and the development of "Wilson's" version of the single-lens screw-barrel microscope can be attributed to more than a few other contemporaneous makers both within and without the British Isles. There is little doubt that, based upon contextual seriation of the form and the absolute dating of some "directing fossil" instruments, these occurrences should be pushed back by at least a decade and perhaps even more. Evidently, the attribution of this pattern to Hartsoeker and Wilson goes back to a brief mention by Mayall and his "Cantor Lectures,” (1886, p. 1034-6), from him to Clay and Court (1926), and later to be copied uncritically by almost everyone who followed.

Wilson (1702) described his first version of the screw-barrel microscope without any reference to Hartsoeker's "invention" (and for good reasons as we saw). A careful reading of his article shows that he also made no claim to originality. As much as the first description of the original form by Hartsoeker (1694: 174-7)  should not be understood as the year of the invention, Wilson's article should not be regarded merely as the absolute date for the introduction of this model in Britain. Moreover, some signed examples made by Edmund Culpeper bear dates as early as 1700. Judging by some of their features, some early forms by Scarlett seem to be contemporaneous with Culpeper's, as well as some instruments from continental Europe (e.g., Golub No. 62). Therefore, it seems that the Italian idea of the screw-barrel microscope but in a single lens form, as well as the German or Dutch concept of the compass microscope, influenced by Leeuwenhoek's and van Musschenbroek's instruments, were taken up by several English makers before 1700. Wilson's publication of 1702 and the pamphlets that followed can be interpreted as a result of this competition, rather than a declaration of an invention (but without any trace of evidence in Wilson's essays). It is high time to remove the name "Wilson" from the screw barrel microscope, as much as there is good reason to avoid the name "Ellis" from the aquatic microscope, first developed for Abraham Trembley (Ratcliff 2009: 103-123).  

From Hartsoeker (1694)

Nicolaas Hartsoeker (1656-1725)

From Wilson (1702)

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According to Clay & Court (1932: 45-49), Wilson's screw-barrel microscopes present three subsequent developmental stages: 

The first type described by Wilson (1702, the figure above), came with a compass microscope where the lenses were mounted on a fork-shaped spike. The screw-barrel microscope had a cork divider between the two brass plates where the slider was intended to be housed.

The second type described by Wilson (1706) is represented by MHS 17260 and perhaps also No. 17 in Giordano (2012: 38-9). A fitting etui with sliders (MHS 30819) most likely accompanied this set. This type had already a thick leather divider instead of the cork one, and the brass handle was shared between the two instruments.

The third type described by Wilson in a pamphlet published sometimes between 1706 and 1710 (Clay & Court 1932: 46). It is represented by Wellcome M0010947. Here, a special lens holder for viewing opaque specimens was added together with a two-sided sample holder, one featuring small forceps and the other being a sharp spike where an insect or a plant can be skewered. One side of the lens holder was screwed into the lens bore, to the other a lens was screwed facing the sharp or forceps end of the specimen holder. The latter was placed into a slot within the thick leather divider, hence it could be focused by turning the barrel. This apparatus made the compass microscope unnecessary, thus third-generation screw barrel microscopes (as the one is seen here) were not supplied with a compass microscope anymore. The lens and specimen holders for opaque objects were significantly improved by Edmund Culpeper and Edward Scarlett, making the slotted thick leather divider unnecessary. 


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

  • Giordano, R., 2012, The Discoverers' Lens: A Photographic History of the Simple Microscope 1680 - 1880. Tallmadge, OH: Classical cience Press.

  • Wilson, J. 1702. The Description and Manner of Using a Late Invented Set of Small Pocket-Microscopes, Made by James Wilson. Philosophical Transactions of the Royal Society of London 23: 1241-1247.

  • Hartsoeker, N. 1694. Essay de Dioptrique. Paris.

  • Ratcliff, M.J., 2009, The Quest for the Invisible: Microscopy in the Enlightenment, Farnham.

  • Mayallת J. Jr. 1886. Cantor Lectures, The Microscope. Journal of the Society of the Arts XXXIV (various pages).

  • Wilson, J. 1702. The Description and Manner of Using a Late Invented Set of Small Pocket-Microscopes, Made by James Wilson; Which with Great Ease are Apply'd in Viewing Opake, Transparent and Liquid Objects: As the Farina of the Flowers of Plants, etc. The Circulation of the Blood in Living Creatures, etc. The Animalcula in Semine, etc. Philosophical Transactions of the Royal Society of London 23: 1241-1247.

  • Wilson, J. 1706. The description and manner of using Mr. Wilson's sett of pocket-microscopes, lately publish'd in the Philosophical Transactions, no 281, and mention'd in no 284, 285, &c. Which microscopes are with great ease apply'd in viewing opake, transparent and liquid objects: ... London.

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