FEMS Microbiology Letters, 362, 2015, fnv113
doi: 10.1093/femsle/fnv113
Advance Access Publication Date: 13 July 2015
Commentary
C O M M E N T A R Y – Professional Development
And then there were 12—distinguishing Van
Leeuwenhoek microscopes from old or new copies
Lesley A. Robertson∗
Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, the Netherlands
∗ Corresponding author: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, the Netherlands.
Tel: +31-15-2782421; E-mail: [email protected]
One sentence summary: Commentary on features of microscopes made by Van Leeuwenhoek that may be useful in authenticating newly discovered
models.
Editor: Rich Boden
ABSTRACT
In the wake of announcements of the authentications of two previously unknown Van Leeuwenhoek microscopes in one
month, this paper reviews the possibilities and potential pitfalls that might be involved in distinguishing 17th/18th century
single-lensed microscopes from historical and modern copies. It is clear that a combination of characteristics must be
considered, no single parameter will do.
Keywords: single lens microscopes; Van Leeuwenhoek; authentication
INTRODUCTION
Evaluating microscopes
In April 2015, I concluded a paper about the fate of Van Leeuwenhoek’s many microscopes with the words∗∗ ‘. . . could there be
more out there?’ (Robertson 2015a). Little did I know that within
2 months, the discoveries of two more Van Leeuwenhoek microscopes would be announced. First came an emailed press release
from Museum Boerhaave in Leiden that a silver Van Leeuwenhoek microscope had been found in a box of silver articles for a
doll’s house in the UK, and authenticated by the Museum Boerhaave team. Not long after, a letter in Nature announced that
a brass Van Leeuwenhoek microscope had been found in mud
from a Delft Canal, and authenticated by Ford (2015).
As yet, only brief announcements have been published and
it is therefore not possible or desirable to comment on the authentication methods used for these two new finds. However,
since there are two ‘lost’ microscopes which were photographed
in the early 20th century (see below), and others may appear, it
is of interest to examine some of the problems involved in authenticating what is simply a couple of pieces of metal with an
inserted lens (Fig. 1), using microscopes from the ‘accepted ten’
(Robertson 2015a) and known facsimilies as examples.
In his excellent review of the structure of Van Leeuwenhoek microscopes, Van Zuylen (1981) described a silver microscope that
had been in the Optisches Museum der Carl Zeiss in Jena until
1911, but whose whereabouts are not known. From his photograph, it resembled a silver microscope in the Deutsches Museum in Munich, with its focusing screw at an angle to the rectangular lens plate. Van Zuylen claimed that he had included
all known Van Leeuwenhoek microscopes, but did not include
a brass microscope which was shown in the catalogue of the
Nachet collection in Paris (Nachet 1929; Van Seters 1933). It resembled the microscope owned by the University of Utrecht,
and seems to have disappeared when the Nachet collection was
dispersed. This microscope, incorrectly assembled, figures in a
poster currently being offered by various online sellers.
Copies
Drawings of Van Leeuwenhoek’s microscopes (Fig. 2) appeared
in a number of places including a portrait by Verkolije, the
Received: 3 June 2015; Accepted: 6 July 2015
C FEMS 2015. All rights reserved. For permissions, please e-mail: [email protected]
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FEMS Microbiology Letters, 2015, Vol. 362, No. 14
Figure 1. Two of the Van Leeuwenhoek microscopes at Museum Boerhaave in Leiden. Left: a silver microscope given to the Museum after the 1983 ‘Beads of Glass’
exhibition. Right: one of the microscopes owned by the Haaxman family until the 20th century (Backer et al. 2014).
Figure 2. Early drawings of Van Leeuwenhoek microscopes. (A) Detail from a 1686 portrait of Van Leeuwenhoek by Jan Verkolije. (B) Von Uffenbach (1754) (C) A lens
plate intended for use with an ‘aalkijker’. Van Leeuwenhoek (1689) (D) Harting (1859); (E) Detail from the frontspiece of the catalogue for the sale of Van Leeuwenhoek’s
microscopes. Rees (1747) (F) John Mayall (1886).
Robertson
frontspiece of the auction catalogue (Rees 1747; Robertson
2015a) and in von Uffenbach’s account of his visit to Delft (von
Uffenbach 1754). Had any of these drawings been used to make
copies, they would be easy to identify since they show microscopes with two or three lenses. Primitive drawings showing a
single lens were published by Harting (1859) and in the diagram
showing the apparatus for observing the circulation of the blood
in eels and small fish, the ‘aalkijker’ (Van Leeuwenhoek 1689).
The lens plates of the 10 accepted microscopes tend into fall into
two groups—rectangles with fairly straight sides and rectangles
with sides that curve towards the mount attachment at the bottom of the lens plate (Fig. 1). The known copies also fall into
these two groups.
Most known copies seem to date from the late 19th century
or later. In 1886, John Mayall published accurate drawings of
the Utrecht microscope (which falls into the latter group) and
made several copies of it (Fig. 2). Copies of the same microscope
were made and sold by the University of Utrecht instrument
maker, Filibri, at the start of the 20th century (Engelsman 1983),
with the mark ‘Utrecht copie’. Copies made and sold by the Museum Boerhaave in Leiden during the 20th and 21st centuries
are slim rectangles based on one of the Haaxman microscopes
(Robertson 2015a). The 20th century ones are stamped ‘copie,
Leiden’ and those from the 21st century have mobile phone
lenses.
Provenance
Only three microscopes can be directly traced to the auction
held in 1747 (Rees 1747). All three were bought by Dirk Haaxman and were retained by the family until the 20th century. The
paper trails for the other seven vary, but most can be traced to
the early 1800s. Three of the four accepted silver microscopes
have a Dutch silver auction mark from the period 1814–31, long
before any of the known copies were made. Three, including one
of the Haaxman microscopes, have similar arrows stamped on
them (Engelsman 1983; Fournier 2002).
The lenses
All of the ‘accepted ten’ microscopes have biconvex lenses. This
was also true of the 24 microscopes left to the Royal Society
of London in Van Leeuwenhoek’s will (Baker 1739). Obviously,
stronger lenses are closer to spherical, but these are rare. Perhaps because people talk of ‘beads of glass’ or ‘glass balls’ (or
because it is easier), many copies have glass spheres. However,
some modern facsimiles (e.g. those used by the author for photographing and filming samples (Robertson 2014, 2015b) also
have biconvex lenses. Most of the ‘accepted ten’ have lenses
made by grinding and polishing, but the Utrecht microscope’s
lens was blown and includes small air bubbles (Van Zuylen 1981).
Van Seters (1933) described and repeated both techniques, obtaining lenses that resemble those attributed to Van Leeuwenhoek.
Physical structure
It might be hoped that analysis of the metal of the microscopes
could help identification, provided that it is non-destructive.
Van Leeuwenhoek extracted the gold and at least some of the
silver in his microscopes from ores himself (Van Seters 1933;
Schierbeek 1947). Such silver might be expected to be purer
than commercial silver which normally has small amounts of
other metals added to harden it (e.g. sterling silver must con-
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tain 92.5% silver). However, he made many microscopes over
a 40-year period, and he might at some time have bought
some silver or melted down a silver coin or spoon to make
some of them. His brass sheets could have come from different
coppersmiths. Non-destructive methods of metal analysis (including X-ray fluorescence and diffraction and physical properties) are frequently used in archaeology (e.g. Dasgupta and
Mondal 2013), and can also be used to ‘fingerprint’ more recent
metals by checking elemental contaminants or alloy mixtures
(for a review, see Craddock 2009). Of course, contaminants in
metals and the compositions of alloys from a particular time
period might also vary depending on the producer, but some
changes will be linked to changes in technology. For example,
some pre-19th century common contaminants of copper were
reduced or removed once extraction using electrolysis became
common.
The size and shape of the lens plates of the ‘accepted ten’
vary widely (Engelsman 1983; Robertson 2015a). It seems that
Van Leeuwenhoek was aiming at efficient sample and lens holders rather than making beautiful instruments. Perfect symmetry or straight edges on the lens plates could indicate machine
cutting.
The long screws mounting the lens plates on the sample
holders of the ‘accepted ten’ microscopes have been measured
(Engelsman 1983; Fournier 2002). Their pitch varies from 0.46
to 0.97 mm. Interestingly, the three Haaxman microscopes and
the Utrecht microscope (all made of brass) are similar (0.86–0.88
mm), as are three of the silver microscopes (0.6–0.66 mm). This
possibly indicates that they were all cut from the same master
screws. The ends of the screws also vary—some are triangular,
some are rounded and one of the Haaxmans resembles an inverted heart with three holes pierced in it. The original screws
were all handmade, but a single machine made screw should not
immediately eliminate an otherwise possible microscope without other tests as a previous owner might have replaced a missing screw. One of the Munich microscopes has lost its focusing
screw (Engelsman 1983).
CONCLUSION
Anyone faced with authenticating a potential Van Leeuwenhoek
microscope must rue the fact that there is no equivalent to carbon dating for silver, brass or glass, although it is possible to discriminate between modern and 17/18th century metals. Did he
use some of the broken window glass left after the explosion
of the military gunpowder store that flattened much of Delft in
1654, or did he use broken drinking vessels to make his lenses?
It is not even certain whether Van Leeuwenhoek always hammered or cut his own lens plates, so there are no metal-working
patterns that could be used as patterns of brush strokes are used
in the authentication of paintings.
The microscope must resemble accepted Van Leeuwenhoek
microscopes, but must not be identical to any of them. Too many
physical matches will indicate that the candidate is a copy, as
will strange analytical results. For example, the facsimiles used
by Robertson (2014, 2015b) for photography and filming resemble different accepted microscopes as closely as possible, even
including the method used to make the lenses (Loncke 2006a,b).
However, careful attention to the properties discussed here immediately reveals their modern nature. Not only do their measurements match existing microscopes, but the chemical composition of their brass and silver is modern, as is the glass of
their lenses.
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FEMS Microbiology Letters, 2015, Vol. 362, No. 14
I look forward to the publication of the analyses of the ‘new’
microscopes, and wish their owners and researchers good luck!
Conflict of interest. None declared.
REFERENCES
Backer J, Biemans C, van Doorn J, et al. Van Leeuwenhoek. Groots in
het kleine. Amsterdam: Veen Media, 2014.
Baker H. An account of Mr Leeuwenhoek’s microscopes. Phil
Trans 1739;41:503–19.
Craddock PT. Scientific Investigation of Copies, Fakes and Forgeries.
Oxford: Routledge, 2009.
Dasgupta P, Mondal BN. Non-destructive studies on Mughal silver coins. Sci Cult 2013;79:512–7.
Engelsman SB. Leeuwenhoek’s microscopes. In: Bracegirdle B
(ed). Beads of Glass: Leeuwenhoek and the Early Microscope. Leiden: Museum Boerhaave, 1983, 28–40.
Ford BJ. The mystery of the microscope in mud. Nature
2015;521:423.
Fournier M. De doos van Pandora. Een microscoop van Antoni
van Leeuwenhoek. Gewinia 2002;25:70–4.
Harting P. Das Mikroscop. Braunschweig: Friedrich Vieweg und
Sohn, 1859.
Leeuwenhoek A. Natuurs Verborgentheden Ontdekt. Delft: Andries
Voorstad, 1689.
Loncke H. Lensje maken deel 4, of maak zelf een Van Leeuwenhoek microscoop. Microwereld Oktober 2006a;46:1–13.
Loncke H. Lensje maken, deel twee. Microwereld 2006b;44:
6–15.
Mayall J. Cantor lectures. The microscope. Lecture II. J Soc Arts
1886;34:1007–21.
Nachet A. Collection Nachet Instruments Scientifiques et Livres Anciens. Paris: Georges Petit, 1929.
Rees A. Catalogus van het vermaarde cabinet van vergrootglasen met
zeer veel moeite, wen kosten in veele jaren geı̈nventeert, gemaakt,
en nagelaten door wylen den Heer Anthony van Leeuwenhoek.
Delft: Reinier Boitet, 1747.
Robertson LA. Historical microbiology, is it relevant in
the 21st century? FEMS Microbiol Lett 2015a;41: issue 9,
DOI: 10.1093/femsle/fnv057.
Robertson LA. Through Van Leeuwenhoek’s Eyes. Oxford University Press, 2014. https://www.youtube.com/watch?v=
OniSF8QrHac (date last accessed, 15 July 2015)
Robertson LA. Van Leeuwenhoek microscopes—where are they
now? FEMS Microbiol Lett 2015b;41: issue 9, DOI: 10.1093/
femsle/fnv056.
Schierbeek A. Van Leeuwenhoek’s schenking van 26 microscopen aan de Royal Sociëty. Ned Tijdschr Geneeskd.
1947;91:708–9.
van Seters WH. Leeuwenhoecks microscopen, praepareeren en
observatiemethodes. Ned Tijdschr Geneeskd 1933;77:4571–89.
von Uffenbach ZC. Merkwürdige Reisen durch Niedersachsen, Holland und Engelland Band 3. Ulm: Gaum, 1754.
van Zuylen J. The microscopes of Antoni van Leeuwenhoek. J
Microsc 1981;121:309–28.