What happened to his papers?

Did Leeuwenhoek leave any unpublished letters?


Unfortunately, his papers are lost. His November 17, 1721, will states:

Ook is ons begeerte dat men in een kist ofte koffer sal opsluyten alle de ongedrukte schriften ende brieven, bij mij Leeuwenhoek sijn geschreven, rakende mijne ontdekkinge, nevens tien gesnede koopere plaaten, behoorende tot eenige ongedrukte brieven, waarvoor men seer na vijfhondert gulden heeft betaelt alsmede de vertaling in 't Latijn, daar men een hondert ende seventig guldens voor betaalt heeft ende dat soo lange als den schelm (dit woord is later door Leeuwenhoek geschrapt) Adriaan Beman in 't leven is, ende en sullen die brieven ende die naderhand nog geschreven sijn, ook niet mogen gedrukt werden bij desselfs soon ofte nabestaande.

It is our desire that in one box or suitcase will be closed up all the unpublished writings and letters, written by me, Leeuwenhoek, concerning my discoveries, and ten cut copper plates, belonging to some unpublished letters, for which was paid more than five hundred guilders as well as the translation into Latin, for which was paid seventy guilders and that so long as the villain [word deleted later by Leeuwenhoek] Adriaan Beman is living, both those letters and those still to be written afterwards, may not be printed by his son or next of kin.

From 1693 to 1702, Leeuwenhoek had published half a dozen volumes of letters printed by his next door neighbor Henrik van Krooneveld. For his Send-Brieven in 1718, he used Adriaan Beman. That relationship apparently did not go well and he died with another volume almost ready for publication.

Maria, as it turned out, survived her father by twenty years. Her will followed the spirit of her father's, though she had to make changes because several of the earlier beneficiaries had died. As he had instructed, the executors of her estate sold his microscopes "in a bundle" at auction. The Catalogus (left; click to enlarge) listed over two hundred lots of microsopes and their storage cabinets. Pre-auction, it was distributed via booksellers and auction houses in several Dutch cities in additiont to Delft.

The last page of the Catalogus (below right; click to enlarge) noted that the auction brought in a little more than 730 guilders. It had a nota bene concerning the papers that Leeuwenhoek left behind.

N.B. In den Boedel van wylen Juffr. Maria van Leeuwenhoek zyn gevonden eenige nagelate Manuscripten of Brieven van haar Vader, den Heer Anth: van Leeuwenhoek, dewelke door zyn Ed: in deszelfs Leven geschreven en in eene nette en goede ordre geschikt zyn, om als een vervolg op zyne voorgaande uitgegeve Brieven gedrukt te konnen werden; Alle de Platen daar toe behoorende, zyn daarby, en reeds in 't koper gegraveert, zoo als ook de Latynsche Vertaling van voorz. Brieven. Iemand genegen zynde, dit Werk te kopen, om het als een vervolg op zyne reeds uitgevene Brieven te laten drukken, kan zich addresseeren aan de Executeurs van de voorsz. Boedel.

N. B. In the estate of the late Miss Maria van Leeuwenhoek were found some manuscripts or letters left behind by her father, Mr. Anth. van Leeuwenhoek, which were written by him in his life and are arranged in neat and good order, to be able to print as a continuation of his previously published letters. All the plates belonging to these, are with them, and are already engraved in copper, as also the Latin translations of these letters. Someone being favorably disposed to buy this work, in order to have printed a continuation of his already published letters, can address himself to the executors of this estate.

Apparently, no one was interested because there is no record that anyone bought this lot at the auction. Nor were any posthumous letters published, so the box of unprinted letters must have been thrown away, perhaps burned, and the copper plates re-used for another purpose.

Twenty years earlier, in a note on pages 725 and 726 of Oudheden en Gestichten, Hugo van Rijn (who translated Leeuwenhoek's Send-Brieven into Latin) related that he had translated these unpublished letters. Even then, in 1725, Van Rijn hoped that the letters would be published.

Gelijk ik ook, op zijn verzoek, noch een groot getal van brieven vertaalt heb, dewelke noch ongedrukt zijn; doch, zoo als ik hoope, en den Liefhebberen der Natuurkunde toewensche, in 't kort door den druk zullen gemeen gemaakt worden.

As I have also translated, at his request, a large number of letters, which are still unprinted; yet, as I hope, and the Devotees of Physics wish, will shortly be shared through the press.

Which letters?

In Letter L-471 280 of 10 September 1709 to John Chamberlayne, Leeuwenhoek wrote, "Since my last printed letters I send to you I have not had anything printed, and I do not intend to have it done, although I have spent more than five hundred guilders on the cutting of copper plates which remain lying here."

This, in 1709, Leeuwenhoek wrote that since publication of Sevende Vervolg der Brieven in 1702, he had not published anything himself, but that he had an unknown number of letters and 500 guilders worth of copper plates.

In those seven years, L. wrote about three dozen letters with observations, almost all of them to the Royal society or directly to his translator John Chamberlayne. Almost all of them were published in Philosophical Transactions soon after the Royal society received them.

He would send another dozen letters to the Royal Society over the next three years, until Edmond Halley took over as Philosophical Transactions editor in November 1713, and Leeuwenhoek realized that he had little chance of publication.

He then proceeded to write and publish the 46 letters in Send-Brieven.

Did he also make plates for the dozen letters between 1709 and 1712?

Are these the letters referred to in the 1747 catalogue?

One of them may be Letter L-475 283 of 21 February 1710 to the Royal Society: "I again take the liberty to send you my following observations such as they were committed to paper by me three years ago, and also the figures I caused to be drawn at that time and engraved on a copper plate."

Letter L-521 317 [XVIII] of 28 September 1715, he writes to Leibniz, ““I intend to have nothing printed in our language, but after my death more than a hundred letters will be made generally known in print and to that end I have already ordered eleven copper plates to be cut; so that now nothing is published but what I write to the Royal society in London, and that is in the English language.”

In Send-Brieven the following footnote was printed on p. 168: Door aanrading van goede vrienden ben ik van voorneemen verandert (at the advice of good friends I have changed my plans), which led to the publication of the Send-Brieven.

There seem to be two obvious possibilities:

  • Were they the batch of four dozen between the last letter in Sevende Vervolg in 1702 and the first letter in Send-Brieven in 1712? Leeuwenhoek addressed almost all of them either to the members of the Royal Society or to his translator there, John Chamberlayne.
  • Because Leeuwenhoek published only 40 letters in both Philosophical Transactions and his own volumes, these unpublished letters in Maria's estate could have been letters recording new observations.

However, at least some of them would have been sent to the people they were addressed to. No such letters have surfaced, so perhaps the 1702-1712 letters are the better bet. In that case, we lost very little because most of them were excerpted in Philosophical Transactions and all the manuscripts are still available at the Royal Society.