Daniel van Gaesbeeck wrote Letter L-149 about why he was publishing more of Leeuwenhoek's “mutilated”, “mistranslated”, and “misunderstood” letters

July 24, 1684

In this open letter from the printer to the reader, but clearly directed toward Leeuwenhoek, Van Gaesbeeck explains why he is publishing some of Leeuwenhoek’s letters. Comparison of Leeuwenhoek’s manuscripts with the extracts translated into English for Philosophical Transactions and Philosophical Collections, summarized in French for Journal des Sçavans, and translated into French and Latin for other publications, shows how much of L.’s writing was “mutilated”, “mistranslated”, and “misunderstood”. Through the efforts of some unnamed gentlemen, Van Gaesbeeck was able to obtain some letters to publish in Dutch, apparently with Leeuwenhoek’s permission. Van Gaesbeeck continues by summarizing the six letters that he printed that year under four separate titles.


From the printer to the reader


Curious reader


The saying, The least is seen, the most remains concealed[1], overwhelmed my zeal with a wondrous desire to contemplate the invisible created truths of essential matter, which was demonstrated to the world through the magnifying instrument (first invented by the ingenious gentleman Ant. Leeuwenhoek to such perfection, to the glory of the city of Delft): whereby the Royal knowledge-seeking Society in London has found itself obliged to accept and embrace his Honor with joy as a worthy confrère in the Society, and to dispense the inventions to the world in Philosophical Transactions (though mutilated[2]). Whereby the excellence of the learned coming together in Leipzig has been encouraged to request the discoveries of his Honor and to publish some of the same in the Ephimeridis Eruditorum[3] (often mistranslated): Many French and Latin writings[4] reported the discoveries, but misunderstood the meaning and essence of the aforesaid gentleman: so that many distinguished and learned gentlemen strongly urged his Honor to make some [discoveries] known to us communicated in his own language in our homeland. So some were recently imparted to me by an eminent gentleman[5], to the satisfaction of my zeal, that I made public to the world through my printing press, and dedicate again to the honored inventor, A. van Leeuwenh. Which his Honor suggested.

The structures and workings of yeast, blood, lobster eye, the coming forth of animals beyond the light, written to Sir T. Gale. Sec. of the Roy. Society, 14 Feb. 1680[6].

Also the shapes of the wine lees, wine, mute wine[7], and blood syrup, and water, of the venae lactae, or the milk-vessels, and the chylus, or milk, of the urine and predictions of the same, of the mist in the air, a burning candle, of the deer’s shape and workings, of living animals in the male seed of cockchafers, damsel flies, grasshoppers, fleas, mosquitoes, of the flea bite, of the animals of which 1,000,000,000 exist in the size of a grain of sand, written to Mr. R. Hooke, Sec. of the Roy. Soc. on 12 Nov. 1680[8].

And on top of that, another treatment of the living animals between our molars and teeth, of the eels in vinegar, pustules in the mouth, of the scales on our skin and their shapes, and the sweat-holes in the same, written to Sir F. Aston. Sec. of the Roy. Soc. on 12 Septemb. 1683[9].

So is his Honor moved at last, by the solicitation of many learned and famous gentlemen, to hand over some of this letters, in order to publish the same to the world through my printing press, so his Honor presented me with an account written to Mr. F. Aston, secretary of the Royal Society in London.

Treating the makeup of the crystalline humor, so of various animals, birds, and fishes, the screw-like creature that appears in the eye, the moisture on the cornea, the makeup of a small vein of blood, and the outer skin of a black Moor[10].

My yet favorable promise to the satisfaction of the knowledge-seeking gentlemen,

The anatomy, growth, and death of various woods[11].

Hoping through the further intercession of various honorable gentlemen to receive the favor of his Honor, in order to obtain more from his Honor, to the delight and satisfaction of knowledge-seeking enthusiasts, then [reader] use it meanwhile to your advantage. And




From my printing shop

on 24 July 1684


Daniel van Gaesbeek.


[1] This saying is found in several other contemporaneous publications. De Brune, “Aan de Lezer”, Wetsteen der vernuften, First Part, p. [xii]; De Bie, Faems weer-galm der Neder-duytsche poësie, p. 271; Swammerdam, Bybel der natuure of historie der insecten, Part 2, p. 785.

[2] For example, Henry Oldenburg translated and published less than half of L.’s famous Letter 26 [18] L-040 of 9 October 1676, Collected Letters, vol. 2, about the microorganisms he discovered in spice infusions. In Letter L-118 to L. of 16 March 1682, in this volume, Robert Hooke writes about his translations of Letter 66 [34] L-114 of 4 November 1681 and Letter 67 [35] L-116 of 3 March 1682, both in idem, vol. 3, “I have not exactly followed your letter word for word in the translation, but as near as possibly I could I have expressed the true sense of your expressions.”

[3] The French-language Le Journal des Sçavans was published in Amsterdam. A Latin translation titled Le Journal des scavans, hoc est: Ephemerides eruditorum was published in Leipzig from 1667 to 1671. The Journal, during L.’s time issued weekly on Mondays, had summaries and translated excerpts from nine letters by L., seven written to Henry Oldenburg and the last two to Robert Hooke. Three of the letters had figures, for a total of ten figures, but no figures were published in Le Journal des Sçavans. For details, see Anderson, Lens on Leeuwenhoek https://lensonleeuwenhoek.net/content/journal-des-scavans.

[4] Prior to 1684, L.’s letters appeared in only one other journal in French and one in Latin. “Observations Faites avec le Microscope sur le sang et sur le lait, by A. van Leeuwenhoek”, Recueil d’experiences et observations, published in 1679, contains excerpts selected, translated, and edited by Louis le Vasseur from Philosophical Transactions, Letter 5 [3] L-006 of 7 April 1674, Letter 8 [4] L-011 of 1 June 1674, Letter 9 [5] L-012 of 6 July 1674, Letter 18 [12] L-026 of 14 August 1675, Collected Letters, vol. 1, and Letter 37 [23] L-067 of 14 January 1678, idem, vol. 2. In 1682, Otto Mencke published “Observationes Microscopica”, Acta eruditorum, vol. 1, p. 321-27, a Latin translation of parts of Letter 65 [33] of 12 November 1680 with the same seven (of eight) figures as in Philosophical Collections, redrawn. “Observatio Dn. Leuwenhoeck De Pilis”, idem, vol. 2, p. 511-12, has a Latin translation of parts of Letter 66 [34] L-114 of 4 November 1681 with the same four figures as in Philosophical Collections, redrawn. Both letters are in Collected Letters, vol. 3. Mencke would publish Latin translations of parts of 11 other letters from L. in later volumes of Acta eruditorum between 1685 and 1689.

[5] Based on Van Gaesbeek’s dedication written earlier in 1684, this gentleman is Cornelis ’s Gravesande. See Letter L-145 of 1 January 1684, n. 1, in this volume.

[6] Van Gaesbeek has the wrong month. Letter 62 [32] L-108 of 14 June 1680, Collected Letters, vol. 3, was published in his Ondervindingen en Beschouwingen der onsigtbare geschapene waarheden, etc. This publication also contained Letter 65 [33] L-111 and Letter 76 [39] L-135 (see below, n. 7 and n. 8), although variants exist. See Anderson, Lens on Leeuwenhoek


[7] Mute wine (stomme wijn) still contains unfermented sugar. See Letter 65 [33] L-111 of 12 November 1680, Collected Letters, vol. 3, p. 285, n. 7. For a discussion of the Dutch trade in adulterated wines, see Henriette de Bruyn Kops, A spirited exchange the wine and brandy trade between France and the Dutch Republic in its Atlantic framework, pp. 131-135.

[8] Letter 65 [33] L-111 of 12 November 1680, Collected Letters, vol. 3. Published in Ondervindingen en Beschouwingen der onsigtbare geschapene waarheden, vervat in verscheydene Brieven, geschreven aan de Wijt-heroemde Koninklijke Societeit in Engeland, printed by Gaesbeek in 1684.

[9] Letter 76 [39] L-135 of 17 September 1683, idem, vol. 4. Published in Ondervindingen en Beschouwingen der onsigbare geschapene waarheden, Waar in gehandeld werd vande Eyerstok ende derselver ingebeelde Eyeren, etc. This publication also contains Letter 70 [37] L-122 of 22 January 1683.

[10] Van Gaesbeek’s summary is almost identical to the summary in the published letter. Letter 80 [41] L-147 of 14 April 1684, ibidem. Published in Ondervindingen en Beschouwingen der onsigbare geschapene waarheden, waar in gehandeld werd Over het maaksel vant Humor Cristallinus, etc.

[11] The only letter prior to 1684 that discusses the anatomy of various woods is Letter 54 [29] L-097 of 12 January 1680, idem, vol. 3. However, it was first printed in Dutch by Cornelis Boutesteyn in 1686 in Ontledingen en Ontdekkingen van Levende Dierkens in de Teel-deelen van verscheyde Dieren, etc.. Of the six letters that Van Gaesbeek published, the two not noted here are Letter 70 [37] L-122 of 22 January 1683 to Christopher Wren (published in Ondervindingen en Beschouwingen der onsigbare geschapene waarheden, Waar in gehandeld werd vande Eyerstok, see n. 8 above) and Letter 79 [40] L-144 of 28 December 1683 to Francis Aston (published in Ondervindingen en Beschouwingen der onsigbare geschapene waarheden, waar in gehandelt wert vande Schobbens inde Mond, etc.