1685: Being ignorant of all other men's thoughts

1685 - "Being ignorant of all other men's thoughts, he is wholly trusting to his own"

In early 1685, Thomas Molyneux visited Leeuwenhoek at his home in Delft. A student at the university in Leiden, Monyneux was the 24-year-old brother of Royal Society fellow and Halley ally William Molyneux. The young man reported back to the Royal Society about Leeuwenhoek:

His only secret I believe is in making clearer glasses, and giving them a better polish than others can do.

I found him a very civil complaisant man, and doubtless of great natural abilities; but, contrary to my expectations, quite a stranger to letters, master neither of Latin, French or English, or any other of the modern tongues besides his own, which is a great hindrance to him in his reasonings upon his observations; for being ignorant of all other men's thoughts, he is wholly trusting to his own, which, I observe, now and then lead him into extravagances and suggest very odd accounts of things, nay, sometimes such as are wholly irreconcilable with all truth.

No doubt Leeuwenhoek had a different impression of such a visit from a representative of the Halley camp of mathematics-oriented researchers, a young man half his age who presumably spoke less Dutch than van Leeuwenhoek spoke English. While there is no record of Leeuwenhoek's side of the story, Molyneux also reported:

Such were the microscopes, which I saw, and these are they he shews to the curious that come and visit him; but besides these he told me he had another sort, which no man living had looked through setting aside himself; these he reserves for his own private observations wholly, and he assur'd me they performed far beyond any that he had shewed me yet; but would not allow me a sight of them.

Read the complete report. It is from such reports that Leeuwenhoek got the reputation for being secretive and amateurish. Perhaps he just lacked patience with snippy young foreigners.

And what happened next? Molyneux' letter was read to the Royal Society in early 1685. After that, there would not be another letter by Leeuwenhoek published in Philosophical Transactions until early 1693.

On 20 July he sailed from Billingsgate to Rotterdam, visited Amsterdam, Haarlem, and Utrecht, and finally entered at the university of Leyden. While there next year he met Locke, who afterwards wrote a letter to him from Utrecht on 22 Dec. 1684, thanking him for his kindness. In the 'Philosophical Transactions,' No. 168, he published an essay on a human frontal bone in the museum at Leyden, of extreme size and thickness, an example either of Parrot's disease or of the osteitis deformans of Paget. On 14 March 1685 he made a report to the Royal Society on the collections of Swammerdam and Hermann, and in the same year went to Paris, where he stayed till his return to London in March 1686.


  • the three letters of January 5 and 23, 1685 (AB 82, 83), and March 30, 1685 (AB 84) were addressed to the members of the Royal Society. William Musgrave published them in volume 15 of 1685.
  • the next two -- July 13, 1685 (AB 85) and October 12, 1685 (AB 88), also addressed to member of the Royal Society, were published by Richard Waller in volume 17 of 1693. (See Period 5.)

Two to Heinsius in August and September

The situation was such at the Royal Society that both secretaries, Aston and Hooke, resigned on December 9, 1685. They were replaced a week later by John Hoskins and Thomas Gale. Seven years were to pass before Leeuwenhoek would have another letter excerpted in Philosophical Transactions.

What happened?
Date Event
January 1, 1685 Published Zaden van Boomen (Seeds of Trees), Letters 46, 47 (L-160, L-166)
January 1, 1685 cousin Maerten Huijchs Leeuwenhoek appointed tax farmer
January 1, 1685 Published Onsigtbare Verborgentheden (Invisible Mysteries), Letters 38, 42, 43 (L-152, L-150, L-128)
January 1, 1685 Published Anatomia et Contemplatio (Anatomy and Contemplation), Letters 43, 42, 38 (L-128, L-150, L-152)
January 1, 1685 Published Sout-figuren (Salt figures), Letters 44, 45 (L-154, L-157)
January 17, 1685 The Royal Society read the latter part of Letter L-150 about the brain of an ox and a sparrow, moxa, chalk from gout, leprosy, and eels, in which he discovered both scales and fins
January 31, 1685 The Royal Society read the former part of Letter L-152 about salts in vinegar and wine, vinegar eels, and salts found in vinegar mixed with crabs eyes and chalk
February 5, 1685 Visited by Thomas Molyneux on behalf of the Royal Society
February 7, 1685 The Royal Society read and discussed the latter part of Letter L-152 salt in various wines, mixtures of tartar, crabs eyes, or chalk with wine, and the difference between salts in wines and salts in chalk stones of gout
February 23, 1685 At age 52, his 25th article in Philosophical Transactions
April 4, 1685 The Royal Society read the former part of Letter L-154 about salts in wormwood, alum, and other substances
April 20, 1685 At age 52, his 25th letter in Philosophical Transactions
May 9, 1685 The Royal Society read part of Letter L-154 about oil of tartar, potash, and camphor
May 16, 1685 The Royal Society read the latter part of Letter L-154 about salts in ashes, lime, soda, and sal armoniac
May 28, 1685 The Dublin Philosophical Society asked the Royal Society for a copy of Letter L-154 about salts of wine and vinegar
June 20, 1685 The Royal Society read part of Letter L-157 about the role of eggs and male sperm in a female dog
July 2, 1685 sister Catharina Leeuwenhoek appointed as tax collector for three years
July 11, 1685 cousin Adriaen Lambrechts Leeuwenhoek appointed curator
August 27, 1685 editor Edmond Halley did not publish any letters by Leeuwenhoek in Philosophical Transactions from 1685 to 1693
November 14, 1685 The Royal Society read and discussed Letter L-159 about reproduction of trees, comparison of reproduction of mammals with the reproduction of plants, and cross-breeding
December 25, 1685 cousin Elisabeth Maertens Leeuwenhoek married Dirck van Schie
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Related letters:
What Leeuwenhoek wrote ...
Wrote Letter L-152 of 1685年01月05日 to Members of the Royal Society about salts in wine and vinegar and in the stomach, the eye, the need for food and water, Descartes's theory on smallest water particles, and a theory of taste - salt, sour and sweet
Wrote Letter L-154 of 1685年01月23日 to Members of the Royal Society about salts and their crystals and his theory about the causes of taste
Wrote Letter L-157 of 1685年03月30日 to Members of the Royal Society about sperm, the uterus of a bitch, sheep embryos, ovaries in young animals and apples, and his claims that sperm are the life-carriers and that there are male and female sperm
Wrote Letter L-159 of 1685年07月13日 to members of the Royal Society about reproduction of trees, transfer of nutrients, male and female trees, hazelnut, comparing reproduction of mammals with reproduction of plants, cross-breeding, and germination
Wrote Letter L-162 of 1685年08月10日 to Anthonie Heinsius about cochineal
Wrote Letter L-164 of 1685年09月21日 to Anthonie Heinsius about cochineal
Wrote Letter L-166 of 1685年10月12日 to members of the Royal Society about the beginning of plants in seeds; chyle, sweat, about skin, optic nerve, and bile of fish; salts in beer vinegar and lemon juice; and spirits mixed with blood and wine vinegar

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