What happened to his microscopes?

Leeuwenhoek made at least 559 microscopic devices of five different types:

  • 23 aquatic microscopes for viewing fish, eels, and oysters
  • 172 aquatic lenses for the eel- and oyster-viewers
  • 88 loupes
  • 5 multiple-lens microscopes
  • 271 single-lens microscopes, the type most commonly associated with him

Of them, only eleven single-lens microscopes have been authenticated.

Two more may well be Leeuwenhoek single-lens microscopes. The 110x brass on the left sidebar is often accepted as genuine and the other, newly discovered, has not been studied enough to be fully accepted yet as genuine. It is not pictured here.

More than 90% of the microscopes that we know Leeuwenhoek made have not survived.

The Boerhaave Museum in Leiden has the largest collection in any one place, and its library has the best public collection of works about Leeuwenhoek. The aquatic microscope (an eel viewer) and the set of six interchangeable aquatic lenses, all on display in the Boerhaave, are discussed on the "Aquatic" page on the right sidebar menu. The loose lenses came with a red leather case (right; click to enlarge). The lenses may or may not have been made by Leeuwenhoek. As with the two disputed single-lens microscopes, their provenance is not completely certain.

More than 90% of the microscopes that we know Leeuwenhoek made have not survived. That is a huge loss. What happened to them?

In late 1688 (or early 1689), Leeuwenhoek gave two magnifying glasses to Queen Mary (while she was still wife of the Stadtholder of Holland, William of Orange). Although Leeuwenhoek recounted the visit in some detail in 1693's Derde Vervolg, dedicated to Queen Mary, he never mentioned this gift, and there is no trace of the two microscopes.

In 1698, he may have given an eel viewer to Tsar Peter of Russia. He may well have given away other microscopes, though some visitors' accounts note Leeuwenhoek's reluctance to part with any. ______ speculates that the eel viewer given to Tsar Peter came back to the Netherlands in _____ and _____.

Leeuwenhoek bequeathed twenty-six magnifying glasses to the Royal Society. In late 1723, just weeks after his death, Rotterdam merchant Abraham Edens delivered them along with a note from Leeuwenhoek's daughter Maria to the Society's officers in London. The Society duly described and catalogued the gift and Martin Folkes, one of the vice-presidents, wrote an article about it for Philosophical Transactions. Unfortunately, the microscopes seemed to "disappear" from the archives by the mid-1800's.

In 1747, the rest were sold at auction.

The 1747 auction

In the will of November 1721 that Leeuwenhoek made with Maria, he expressed his wishes for his microscopes. They should be sold "in a bundle".

Vorders is ons begeeren dat alle de vergroote glazen geene uytgesondert, die in het cabinet leggen ende meest in cantoortgens sijn opgeslooten met haar comptoirtjens sullen werden op den inventaris gebragt, sonder dat men yder in 't particulier sal op den inventaris te brengen, in een koffer of kist met de gereedschappen, sullen opgeslooten ende versegelt te werden, om tijd ende wijle, na de doot van de langstlevende, soo deselve nog in wesen sijn, in een bondel te verkoopen ten genoege van de heeren executuurs, ende ten meesten voordeel van de nalatenschap.

Further our intention is, that all the magnifying glasses, no exceptions, that lie in the cabinet and mostly are closed up in little containers (cantoorgens) with their [comptoirgens] will be inventoried, without inventorying each one individually, in a case or chest with the instruments, will be closed up and sealed, so that in due course, after the death of the survivor, still being essentially the same, to sell in a bundle to the satisfaction of the gentlemen executors, and to the greatest benefit of the estate.

The executors of Maria's estate complied two years after her death. On May 29, 1747, they held a public auction at the Sint-Lucasgilde on the Voldersgracht. The "Buyers 1747 auction" page on the right sidebar menu lists the buyers and some information about them. A few were brokers, but most were friends and relatives in Delft.

The 26 microscopes to the Royal Society

After Leeuwenhoek's death, two articles in Philosophical Transactions concerned his microscopes. Within a year of his death, editor James Jurin published, in volume 32, "Some Account of Mr. Leeuwenhoek's Curious Microscopes, Lately Presented to the Royal Society. By Martin Folkes, Esq; Vice-President of the Royal Society". It has the only account of the gift to Queen Mary.

Fifteen years later, Henry Baker wrote "An Account of Mr. Leeuwenhoek's Microscopes", which was published in volume 41, 1739. These two articles provide much of what we know about the microscopes. This knowledge has been confirmed by direct analysis of the few surviving. They were probably not among those bequeathed to the Royal Society, all of which seem to have gone missing.

In 2015, Brian Ford's "Leeuwenhoek Microscopes: Mystery and Mischief" recounted his efforts to follow what turned out to be "a cold trail":

The supremacy of Leeuwenhoek’s lenses was still acknowledged in the 1820s, when an eminent surgeon, Sir Everard Home, borrowed them from the Royal Society for his own microscopical studies. I wanted to find out more, and in 1981, Royal Society President Sir Andrew Huxley encouraged me to investigate.

Eventually, I unearthed in the Society’s files a letter dated April 5, 1855 and written by Sir James South. It asked the Society’s secretary to find out where the missing microscopes might be, though it was clear that South was pointing his finger at Home. The Society set up a committee to look into the fate of its property, but they failed to publish their report. Ten years went by and South wrote again on May 10, 1865, but once again he found nothing new — and there the trail went cold.

Home had taken possession of a huge collection of manuscripts left by the anatomist John Hunter, and he was publishing papers describing Hunter’s discoveries as if they were his own in a flagrant act of plagiarism. The Royal College of Surgeons threatened to seize the manuscripts and, rather than admit the facts, Home resolved to burn them all. The flames grew out of control and destroyed his apartment at the Chelsea Hospital. My late colleague Professor Derek de Solla Price of Yale concluded that, because the microscopes were made of silver, they melted away in the blaze.

How much is an authentic Leeuwenhoek microscope worth?

In 2009, Christie's in London auctioned one of Leeuwenhoek's microscopes, the 69x silver microscope that had been acquired from Robert Thomas Maitland. It had been on display in the Boerhaave.

Pre-sale, Christie's estimated a high bid of 100,000 euro. The microscope sold for 313,250 euro, the highest price ever paid for a scientific instrument from the Dutch Golden Age and a testimony to the appeal and significance of Leeuwenhoek today.

In private and institutional collections

Of the over five hundred items in the catalogue, we can trace some of the microscopes in private and public collections over the following century. The "In collections" page on the right sidebar lists dozens of such mentions.

The 1875 Remembrance

The pivotal event occurred in 1875. A committee of Dutch scientists and some historians assembled several hundred artifacts related to Leeuwenhoek. On September 8, 1875, they exhibited them, including seven microscopes (three silver and four brass), in Delft in celebration of the 200th anniversary of Leeuwenhoek's discovery of microorganisms. The following year, one of the committee members, Peter Harting, published a commemorative book that listed all of the items in the exhibit. The microscopes in that exhibit are discussed on the "The 1875 Remembrance" page on the right sidebar.

Before 1875, there had been little interest in scientific instruments as objects of collection and study in general, to say nothing of Leeuwenhoek's microscopes in particular. However, the 1875 celebration of Leeuwenhoek’s achievements sparked the production of copies of the Leeuwenhoek microscopes. Thus, only those mentioned before 1875 can be marked as genuine without doubt.

Since 1875

The seven microscopes from the 1875 exhibit and the three others that have surfaced since are discussed in the "Single-lens microscopes" section on the right sidebar menu. The most important event since 1875 was the 1982 exhibit at the Boerhaave Museum in Leiden. In commemoration of the 350th anniversary of Leeuwenhoek's birth, the museum assembled all eight of the then-extant Leeuwenhoek microscopes. The ninth was identified in the family belongings of a Dutch woman as a result of her visit to the exhibition. In 2013, the tenth was found in a collection of other old instruments.

In 2014, another microscope was discovered in the mud in Delft's muinicipal park, just outside the medieval city walls. It has been studied by Brian Ford, who deemed it authentic. Upon examination by the curators at the the Boerhaave Museum, it was proven to be a copy.

When the next authentic Leeuwenhoek microscope surfaces, it will delight everyone but surprise no one.

The Related Sources below discuss the provenance of the ten fully authenticated microscopes.