What did Leeuwenhoek say about his own writing?
"I have no style or pen"
In the letters, Leeuwenhoek said very little about his own writing and then only at the beginning of his career. In his Letter 2 of August 15, 1673 (AB 2) to Henry Oldenburg, he addressed his shortcomings directly.
I have several times been pressed by various gentlemen to put on paper what I have seen through my recently invented microscope. I have constantly declined to do so, first because I have no style or pen to express my thoughts properly, secondly because I have not been brought up in languages or arts, but in trade, and thirdly because I do not feel inclined to stand blame or refutation from others. Pressed by Dr. Reg. de Graaf I have thought better of my intention.
The advanced study of Latin and Greek would have provided the training in both language and rhetoric that Leeuwenhoek realized he was missing. But it wasn't just writing. His letter was addressed to the Royal Society, scholarly home of Robert Hooke. Leeuwenhoek's first few letters were accounts of his replication of three of Hooke's observations in Micrographia, for which Hooke drew his own figures, and drew them very well. One of the leading microscopists in the Dutch Republic, Johannes Swammerdam, had also corresponded with the Royal Society, as Leeuwenhoek well knew. Swammerdam drew his own figures, too, not as well as Hooke, but still very well.
When he sent his first letter, Leeuwenhoek did not send any figures. When asked to do so by Oldenburg, Leeuwenhoek replied in his second letter:
As I am not a draughtsman myself, I have had them drawn for me, but the proportions have not been observed as accurately as I could have wished. Also each figure has been seen and drawn through a particular magnifying glass; I am sending you these enclosed.
Note that from the beginning, Leeuwenhoek was using a different magnifying glass for each observation. He concluded with a statement that expressed his fears and positioned himself socially.
I beg you and the Gentlemen under whose eyes this happens to come, to bear in mind that my observations and opinions are only the result of my own impulse and curiosity and that there are in this town no amateurs who, like me, dabble in this art. Take my simple pen, my boldness and my opinions for what they are; they follow without any particular order.
With that last phrase, Leeuwenhoek showed his awareness of his lack of skills beyond the sentence level. The first letter he sent had been structured in the same order as the observations in Micrographia that he was replicating. With this second letter, however, Leeuwenhoek was on his own.
"I was not educated in schools and academies"
After that, Leeuwenhoek wrote a dozen letters in 1674 and 1675 without any mention of his education or writing skills. In them, he remarked several times, in passing, about knowing only Dutch.
Letter 13 of December 20, 1675 (AB 19) was addressed to Henry Oldenburg.
This last possibility (since to my regret I do not understand English and in this town there is nobody who is able to translate it into Dutch for me) I inferred from the figures only.
A month later, in the letter of January 22, 1676 (AB 20) to Henry Oldenburg, Leeuwenhoek brought it up again at the beginning of a letter.
Dear Sir, Your letter of the 28th was received by me in good order, from which I learned that you do not doubt my knowledge of French, but I must tell you that I regret I do not understand any language but Dutch. When you write to me in French or Latin I can help myself all right, since I have enough friends who will translate it for me. But I cannot help myself with the English language since the death of a certain gentleman who was proficient in this language.
I admit that usually Englishmen can be found everywhere, but not all are able to translate the Transactions from English into Dutch. Inquiring after a proficient person, I was sent to the precentor of the English church (who also undertakes to teach the English language). This man presuming to be able to do this and having translated something regarding my speculations, it was so badly put that I could not make sense of it.
Six months later, in Letter 17 of July 28, 1676 (AB 25), at the beginning of his first letter to Robert Boyle, Leeuwenhoek felt the need for a final time to address his limited education and language skills.
Right Honourable Sir, Since I learned that Your Worship has honoured me by sending me your greetings through Mr. Secretary Olderburg, and that you were pleased to see me investigating Nature (albeit I was not educated in schools and academies) I take the liberty to send Your Worship my trifling observations. With the help of an English and Dutch dictionary (since I do not know the English language) I understood from Transaction Nr. 1202 that you had put some copper-filings in spirit of salts etc.
After that, Leeuwenhoek mentioned translations a few times, especially Latin translations of his letters. For example, in the letter of October 30, 1676 to Oldenburg, he wrote:
I was very pleased with Mr. Grew's remarks on my letter (albeit I do not understand it) and when I succeed in having it translated, I most certainly will answer him.
In Letter 25 of May 31, 1678, (AB 39) to Nehemiah Grew, who by then had replaced Oldenburg as Royal Society secretary and Leeuwenhoek's contact, he mentioned a dictionary.
In a Dutch-English Dictionary I find Polcat for Bonsen.
This dictionary must have been Hexham's, perhaps the latest 1675 "New Edition Amended, Enlarged, and Enriched with many Words, By Daniel Manly", which had "a Polcat. Een Bonser". Compare with Sewel's 1691 dictionary: "Polcat, de Bonsem". Hexham's is also probably the dictionary Leeuwenhoek referred to in Letter 17.
In the letter of May 15, 1679 (AB 46) to Christiaan Huygens, Leeuwenhoek wrote:
I must not omit telling you that Mr. Robert Hooke last year published a little book entitled Lectures and Collections, made by Robert Hooke, Secretary of the Royal Society. He sent me a copy of this little book. I do not understand English, but it seems to me that in between two letters by me, which are contained in it, he writes about the manufacture and the use of the microscope.
In letters over the following four decades, Leeuwenhoek never again pointed out his lack of education, languages, or writing skills. By the 1690's, there is evidence that his English could have improved. [ add the passage he summarized ]