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Delft’s Science Centre nominated for Museum Prize!

Delft Science Centre with new Kamer van Beijerinck, 2nd floor with balcony

We’re very excited to be able to tell you that the Delft Science Centre, home of the Beijerinck, van Iterson and Kluyver collection as well as the Faculty of Mining’s mineral collection and more modern exhibits from Delft University of Technology, has been nominated for the BankGiro Lottery’s Museum Prize.

It would be very kind and much appreciated if you would support us by voting.

The voting site is in Dutch, so here’s a translation into English for those who use other languages.

1; Go to the site here:

2; Hit the green button labelled “Stem op dit museum”.

3: When the blue rectangle comes up, it says “Yes, I’m voting for the Science Centre Delft” and asks you to fill in your name and then your email address (that’s so that they can make sure that each email address is linked to one vote and so that they can let you know if you win the prize trip to New York).

Also click the box immediately under the email box – it indicates that you’re over 18 and agree with the rules (which you can see by hitting the “actievoorwaarden” link. If you want to read them, copy the text and paste it into Google Translate or another translation app). The two boxes below, if clicked, let them send you news about the BankGiro Lottery (who’re sponsoring the prize) and the Prins Bernhard Culture Fund (also sponsors).

4: Click on the green button.

You will then be thanked for voting and they will send an email to the address you gave them. The email will ask you to click on another green button to confirm your vote (it prevents folk from getting carried away and making up email addresses to let them vote often).

Thoughts on Van Leeuwenhoek’s optical tool box

My personal project to find the descriptions of methods buried in Van Leeuwenhoek’s letters and to try and work out how he did things that he didn’t describe continues. My most recent results have now appeared in the Nov 2017 FEMS Letters with the POI: The paper covers problems encountered with using the classical microscopes with some samples that we know he studied, and suggests a solution.

Antoni van Leeuwenhoek did not limit his research to microorganisms. Indeed, he worked with a very wide range of samples ranging from wood and animal tissues through insects to individual cells and sperm to bacteria. His microscopes work very well with transparent samples where the light can pass through them (and the samples were small) but, as can be seen from Figure 1, he was obviously also using reflected light.

Transmitted and reflected lighting of a gnat

Figure 1A shows a drawing of a gnat, taken from a 1702 Van Leeuwenhoek letter. Figures 1B and C. show a similar insect photographed under a 19th century Carl Zeiss Jena microscope with transmitted (B) and reflected (C) light. It is clear that the level of detail shown by Van Leeuwenhoek cannot be observed on the silhouette shown in B.

The details are all in my papers, but my conclusion is that, as he did with his aalkijkers (his microscopes for viewing the blood in the capillaries of the tails of small eels and fish where the sample pin was replaced by a glass tube to keep the specimen alive), Van Leeuwenhoek adapted his magnifiers to suit the task in hand.

Figure 2 shows a collection of magnifying equipment that I think Van Leeuwenhoek used as his optical tookbox. The photographs show modern facsimiles, the drawings were made during or just after Van Leeuwenhoek’s life. This conclusion is based on experimental results and historical documents.

Figure 2: Optical toolbox

A: This magnifying glass (or something very like it) appears in the frontispiece of the auction catalogue for the sale of Van Leeuwenhoek’s microscopes after his daughter’s death. Because the lens is set into a simple ring rather than the metal plate of the Van Leeuwenhoek microscope, the setting does not cast a shadow on the sample if reflected lighting is used.

B: This version of the Van Leeuwenhoek microscope was published by a German visitor (Zacharius-Conrad von Uffenbach), and microscopes with 2 lenses are mentioned in the sale catalogue. With 2 different lenses side by side, it would have been more convenient than moving a fragile sample to another microscope for a different magnification.

C: This 3-lensed microscope comes from an engraving made while Van Leeuwenhoek was in the prime of life, and is also mentioned in the catalogue. Note the holder for a capillary (used for liquid samples such as blood) beside the sample needle.

D and F: Copies of 17/18th century magnifying glasses, as sold by the Rijksmuseum Boerhaave. “Burning glasses” are mentioned in the inventory of the Van Leeuwenhoek house after Maria van Leeuwenhoek’s death. As well as magnifying larger samples, they can be used to control the lighting of samples on the microscopes.

E: Some of the facsimiles of existing Van Leeuwenhoek microscopes made by Hans Loncke and used in my experiments.

G: Van Leeuwenhoek’s adaption of the eyepiece on his aalkijker to allow reflected lighting while protecting the eye with a small cup.

H: A facsimile of the aalkijker drawn in Van Leeuwenhoek’s first paper on blood circulation. Note the use of the same lens plate as with the microscopes.

I:  His final adaption of the aalkijker to make its use easier for visitors, as mentioned by him in a letter and drawn by Von Uffenbach.

People often describe his microscopes as crude, and perhaps they are when compared to other, ornamented microscopes of his time, but I suspect that Antoni van Leeuwenhoek was more interested in making something that would allow him to carry out his experiments rather than producing elegant instruments.

Van Iterson’s wall chart collection.



In the days before the easy projection of images, wall charts were the usual manner of illustrating lectures and practical classes. This photo shows the autumn 1941 practical on microscopical research of living plants and plant products, with wall charts in use on the back wall. Prof van Iterson can be seen standing in the far left corner of the room.


The Archive has a large collection of these wall charts, and I’ve previously shown some of the printed ones as well as some by Henriette Beijerinck. The original wall charts for Van Iterson’s Department were produced by at least 15 people, not all of whom signed their work with their full names. They range from beautiful watercolours of useful plants to diagrams and tables – everything a Professor of Applied Botany could need for his lectures.


Like Beijerinck and Kluyver, in those days before the discovery of DNA, Van Iterson was interested in heredity and variation, and we have a series of watercolours illustrating Mendelian genetics, gender dimorphism and mimicry.



Researching and cataloguing the wall chart collection was a great labour of love by Truus ten Hoopen-van Hulsentop. If anyone can tell us anything more about the various artists, we’d be delighted to hear from you.

Something Van Leeuwenhoek didn’t see!

On 7th May (2017) the Dutch Society for Microscopy (Nederlands Genootschap voor Microscopie) ran an open microscopy workshop at the Delft Science Centre. They taught members of the public (and me!) how to make thin sections of plant material, stain the sections and then examine them under modern microscopes.

The plant material in question was a twig from Wollemia nobilis (captive bred). W. nobilis is a very rare pine tree that was only known from the fossil record until 1994 when a few trees were found in Australia. The oldest tree has been estimated to be over 1000 years old according to the Kew Gardens website. As the only representatives of a genus that dates back to the time of the dinosaurs, the wild trees are IUCN-red listed and stringently protected, but seedlings can now sometimes be bought.

Since there were a few sections left at the end of the workshop, how could I resist putting them under my 65x facsimile Van Leeuwenhoek microscope?  He would, of course, have examined them if they had been available to him 300 years ago.

A couple of images using a much weaker lens on my 19th century Zeiss “jug handled” microscope have also been included for comparison (the first photo on each line). The red and blue images came from a stained preparation, the others from a section that had been allowed to dry on a coverslip, without staining.

Antoni van Leeuwenhoek in Spain

I have just heard that it will be possible to see part of the beautiful Camacho & Pallas microscope collection at the Museum of Evolution in Burgos (Castille & Leon) in Spain.

The exhibition will run from April to November, 2017.

This is a privately-owned collection which includes the Van Leeuwenhoek microscope that was found in mud dredged from Delft’s Oude Delft canal in in 2015 (see my blogpost from 23 June 2015).

If you’re going to be holidaying in Spain this summer, it’ll be well worth a visit.


Beijerinck’s office (and the neighbours)…

At long last, the Beijerinck Museum is ready for visitors – indeed several groups, including the Dutch Microscopy Society and guests from the Queckett Microscopical Club, have had sneak previews. Also known as “Beijerinck’s Office” (Kamer van Beijerinck), it will only be open to escorted groups as we don’t want to spoil the atmosphere by putting everything into locked display cabinets. Some of our microscopes are now on display in the foyer of the Mekelzaal, the main conference room of the Science Centre.

At the end of BioDay, a meeting organised to celebrate the  TUDelft’s 175th birthday, the Museum was re-opened by Professor Karel Luyben, Rector Magnificus of the University, ably (?) assisted by someone claiming to be Prof Beijerinck’s assistant…

This seems like a good moment to take a look at our new surroundings. We are housed on the second floor of the Delft Science Centre. The building was originally the Faculty of Mining. It’s very easy to feel at home here as, like Prof van Iterson’s section of our previous building, our new home dates from the early 20th century and the design is very similar. The view from our windows is a great improvement!

The main part of the Science Centre  displays the modern achievements of Delft University of Technology and a range of prototypes (including Delft’s famous solar powered car) can be seen as well as displays that can be operated by the visitors. You can try improving the shape of an aircraft wing or use the driving simulators, among many other things – the exhibition often changes. The robotics lab is ever popular, as are the workshops where school groups (among others) come to try things out. For example, the Dutch Microscopy Society will be running a public workshop (about how to make botanic preparations (Wollemia nobilis)  and look at them under the microscope) from 14:00-16:30 on 7th May (2017). Participants will only pay the Science Centre entrance price. The details are here: It’s in Dutch but the site will allow you to copy the text for pasting into Google translate (which is always amusing….).

The TUDelft has always had a  number of internationally important collections which started life as the working tools and products of its research departments. Among them, the minerals collection from the Faculty of Mining (which dates from the middle of the 19th century) is remarkably beautiful. It is housed, in its original display cases, in rooms next door to the Beijerinck Museum and in cabinets in other public parts of the building. Like the Beijerinck Museum, the Minerals Collection is open to escorted groups.

Just around the corner from the Science Centre is Delft’s Botanic Garden. Founded by Prof van Iterson with support from Prof Beijerinck, it was set up to provide plants for research in the Department of Applied Botany and is 100 years old this year (2017). Apart from their permanent collection (which includes an apiary), they frequently have exhibitions ranging from pottery through products made from plant material to photography. Their website is here:

The Science Centre’s website with opening times and other information is here

Exhibition update

The exhibition in the Old Church was opened this morning. It’s a wonderful setting, so close to Van Leeuwenhoek’s grave (where the pinkish light is beyond the pulpit), although the Church dwarfs everything.


When most of the guests had left, we had a surprise guest!


Delft, the Home of Microbiology

An exhibition at Van Leeuwenhoek’s resting place.

2017 is the 175th anniversary of the founding of the Polytechnic School that eventually became Delft University of Technology. The University is celebrating with a 175 day Lustrum, much of which will focus on the Life Sciences. It is also 100 years since Van Iterson founded the Delft Botanic Garden on the land behind his laboratory.

invite lustrum bit e

We are beginning the celebrations with a look at the history of microbiology and the biosciences in Delft, from the 17th to the 21st centuries. The exhibition will run until 26 February, 2017.

invite poster s

This will take the form of an exhibition in the area around Antoni van Leeuwenhoek’s grave in the Oude Kirk.

The text on the poster boards is in Dutch, but there are also English language handouts. It includes 20th century teaching microscopes, a cross section of an electron microscope and  3-D scanned replicates of a Van Leeuwenhoek microscope and the Delft telescope.

Facsimile Van Leeuwenhoek microscope and its 3-D scanned replicate

Facsimile Van Leeuwenhoek microscope and its 3-D scanned replicate

The exhibition offers a taster of the achievements of Delft microbiologists and introduces some of the people who helped and supported them. For example, we might never have heard of Antoni van Leeuwenhoek and his little animals without Reinier de Graaf, the doctor who introduced van Leeuwenhoek to the Royal Society of London, publishers of much of his work. Jacques van Marken not only brought Beijerinck to Delft to establish his industrial microbiology laboratory, he was also one of the people instrumental in creating the Department of Microbiology and Professor’s Chair for Beijerinck at what was then the Delft Polytechnic.

Many others have provided help, support and encouragement, but the silent contributor to the history of microbiology is the City of Delft itself. Many very well-studied microorganisms were found for the first time in samples from Delft’s canals, soil and from industrial sources, even now.

Over 300 years ago, before Van Leeuwenhoek found his little animals, the city was already a hotspot in scientific research-for example Stevin and de Groot dropped different lead balls off the tower of the New Church and proved that they hit the ground at the same time 3 years before Galileo did the same experiment from the tower of Pisa!


Delft’s New Church

What was this microscope used for?

Discovering rare or unusual microscopes has become almost routine since we began packing the collection, but this one has me (and everyone else who has visited) baffled.

It seems to be a “jug handled” Carl Zeiss Jena microscope from the late 19th/early 20th century. However, it is mounted on its back rather than on a foot (1). Moreover, in place of the usual single condenser, there’s what seems to be 2 lenses of different strengths and 2 condensers (2), hinged so that any of them can be used to light the preparation (3). There’s an additional lens which can swing over the usual ocular (4).

Has anyone any idea what it was used for?

From “out of date junk” to “exciting and rare” – our microscope collection

At the moment, sorting out the cupboards before our move has become very exciting as I’ve reached the microscope collection. Much of it was stored in the 1950s when the Laboratory of Microbiology moved from its original building, and has rarely been disturbed since then. Some of the microscopes date from the late 19th century, and even some of the 20th century ones are more interesting than might be expected.

The youngest of the companies represented in our microscope collection is probably the least well-known, especially outside the Netherlands.

Bleeker Nedoptifa

Founded by Dr Caroline E. (Lili) Bleeker and Gerard Willemse in 1939, Nedoptifa rapidly became known for the high standard of their optical products. They began with the production of binoculars for the Dutch army, but production was interrupted by WW2. Most of their microscope production seems to have been after 1945, when the “Nedoptifa” name came into use. The company cooperated with the Nobel prize-winner, Frits Zernike, in the development of phase contrast microscopy and held his patent on phase contrast microscopes. Bleeker retired at the end of 1963, the company was eventually taken over by a Delft firm and then in 1978 the factory in Zeist was closed.

Kluyver’s group seems to have used the basic Nedoptifa microscope for teaching – we have quite a few of them. Most of them have the standard circular stage, but a few are square. We also have one of their very early binocular microscopes as well as monocular and binocular phase contrast microscopes. Most of them, with the exception of the binocular phase contrast microscope, seem to have been use in in the laboratory before 1955.

Note added later: Disappointingly, after a visit in mid-June from Peter Paul de Bruyn, an expert on Bleeker microscopes, it seems that the microscopes whose boxes proclaimed them to be phase contrast microscopes do not have the necessary lenses or fittings. They may appear as we complete the packing of the collection, but it’s beginning to look unlikely.

Carl Zeiss Jena

This famous old microscope manufacturer needs no introduction. In what is probably our most famous portrait of Prof Beijerinck, he is clearly using one of their “jug handled” microscopes. Others in our collection are in the Zeiss catalogues of the late 19th century.

We also have some more unusual examples of their work including a “horizontal microscope” (intended for examining living plants) and a binocular microscope fitted with a prism on the right ocular to aid the drawing of samples.

I really shouldn’t have favourites, but I must admit a fondness for the very heavy preparation microscope that turned up in a battered old wooden box on top of a cupboard. When it is taken out of the box, the eyepieces on the right flip up, giving a forerunner of our modern stereomicroscopes which can be found in the 1902 Carl Zeiss Catalogue. There are 2 sets of lenses and oculars. During dissections, the microscope can be moved backwards and forwards along the metal bar.

Early Zeiss preparation or dissecting microscope

Early Zeiss preparation or dissecting microscope

Ernst Leitz Wetzlar

Another famous old company, Leitz seems to have been a favourite with Professor van Iterson. Among the microscopes from this company are a “measuring microscope”, a preparation microscope with wrist supports and the microscope (with an extensive collection of extra attachments) that he used after he retired.

Other companies

Other microscope makers are mostly represented by single instruments, so I will only show two of the most spectacular. First is the interference microscope made by Cooke, Troughton & Simms from the Van Iterson collection. This microscope is accompanied by a set of extra attachments and filters.

And lastly, one of the most unusual microscopes in our collection, a reversed microscope made by Nachet & Fils of Paris. The sample lies on the stage and can be illuminated from above, with the observer’s light path underneath the stage. It appears in the 1898 Nachet catalogue. This microscope was given to the collection by Dr and Mrs ten Hoopen, both of whom worked in the Department of Applied Botany before volunteering to help with the Archive and Museum after they retired.

The Delft School of Microbiology Archive owes a huge debt to both of them. Truus undertook two major tasks. First she restored our enormous collection of glass negatives (see the blogpost “Glass negatives galore!”) after they all got damp during asbestos removal in the attic where they were stored. She then went on to research and catalogue our collections of original and printed botanic and microbiological wall charts (see blogposts “The art of Henriette Beijerinck” and “Educational Wall Charts – where are they now?”). Meanwhile, Hens catalogued the microscopes and other equipment (we have the most amazing range of pH meters, for example) in our collection.

Without Truus and Hens ten Hoopen, we would know a lot less about the Collection than we do.

Reversed light path microscope by Nachet et fils

Reversed light path microscope by Nachet et fils

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