Wrote Letter 59 of 1687-10-17 (AB 104) to Members of the Royal Society

October 17, 1687
Standard reference information
Cole's number: 
AB/CL number: 
AB/CL volume: 

Text of the letter in the original Dutch and in English translation from Alle de Brieven / The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren.

The original manuscript, written and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1925. L 2. 16).

Reception in London

There is no record in Birch's History that this letter was received or read at a weekly meeting. Leeuwenhoek addressed this situation at the beginning of the letter.

Here you have, Very Noble Sirs, my seventh missive that I have written to Your Honours this summer, without my having received any reply all that time. I should like to hope that the same will not have been unpleasing, and that, in this as in the preceding ones, there may be something that will interest the learned world.

These seven letters, all written in 1687, plus the following Letter 60 of November 28, 1687, were all addressed to the Royal Society but never published in Philosophical Transactions. Leeuwenhoek published them himself later that year under the title Vervolg der Brieven (Continuation of the Letters) and in Latin translation in 1689 in Continuatio Epistolarum.

Specimens from around the world: "Many things defy investigation."

As Leeuwenhoek's fame spread, his specimens came from all over the world. He began this letter:

A certain doctor of medicine, born in Prussia, sends me a very courteous missive, asking to be allowed to visit me; and in addition he sends me some small pieces of amber which, he says, are sent me by two prominent gentlemen in Prussia.

He put this amber under his microscope.

In these pieces of amber there were some peculiar little animals, like tiny flies, a mosquito, a spider, and an ant; and when I examined these little animals through the microscope, I not only saw very clearly the little wings; but also the processes of which the eyes of the said little animals are composed; and further, the legs, hairs, and claws on the same - so distinctly as if one had such an animal standing naked before the microscope. And I also saw a small piece of straw in one of the pieces of amber, in which I was able to recognize the tubules (of which straw consists).

How did the creatures get into the amber? People had explanations, but Leeuwenhoek was accustomed to a view of the world where such explanations did not suffice.

How these little animals get into the amber, and how amber is made, that is unknown to us, and we cannot accept the reasonings of other persons on this point, which does not, in our view, seem plausible; and we have no occasion whatsoever to inquire into it.

Later in the same letter, he wanted to know more about insect bites.

Last year I instructed the workmen who, in this city, receive the goods from the East Indies, to bring me a live centipede, with the intention to discover, if possible, the reason for these harmful bites of the centipede.

He examined this centipede but was not able to answer all of his questions. Discussing Fig. 10, he wrote:

I had intended to continue my observations this year, and to this end I had instructed the workmen to catch the centipedes. But they have not observed any, although several were seen on board ship during unloading of the goods, and were killed there.

I could not omit adding this, because a certain doctor in the Indies writes that many things defy investigation over there, among which he also reckons the harmful bite or nip of the centipede.

I have kept a nipper, or pincer, or sting-like part of the said centipede, in order to be able, if necessary, to show its structure, and I have also thought fit to have it drawn.

Public reception: "What imagination is capable of."

The next part of this letter was a narrative that revealed how Leeuwenhoek worked on a problem. It began, as it often did, with an odd object that a "gentleman" gave to him or, in this case, sent to him. Leeuwenhoek then gathered relevant evidence and followed a line of reasoning that led to a clearly stated conclusion illustrated by a figure.

The same gentleman told me, amongst other things, that there had fallen from the sky, on a field in Courland, on the 14th or 15th of March 1686, a piece of burned paper which was quite three sheets large, of which, so he said, he had a piece that he had observed through the microscope; but that he was unable to form an opinion of it. And as I made it clear that I would like to see this alleged paper, the said gentleman sent me a piece (by letter), of which I hereby enclose about half.

I had not had this supposed paper in my house for half an hour before I had (with the aid of the microscope) formed such a clear idea of it, that I fancied it to be a plant which had come forth from the water. And moreover I took it for sure that, if it were true that it had fallen out of the sky on to the field, then this substance must first have been driven up into the air (by a cloud which we call a whirlwind).

But I much rather believe that, owing to heavy rains, or melting snow (if the country is a mountainous one), the water from a morass or from ditches, has flooded some piece of land, and that the water had left this green plant, from which the so-called paper is made, behind on a greensward or a field with young corn, with the result that the sun and wind caused the plant to become dry and stiff, so that it took on to some extent the look of burned paper. And I also concluded that I had often seen this substance in large quantities in certain stagnant waters, such as ditches, and excavated lands; but what puzzled me was how I could possibly make this substance, or green plant, turn into a blackish mass. This green plant is often called felt, but more often, phlegm by the common man.

To satisfy myself on this point, I bethought myself of going to some marshy fields, situated not far from our city: But on reflecting that the canals that run around our city, have sluice-gates in two distinct places, in order that the daily current of water shall run not around, but through our city: I went to where the water in the city canal had the least movement, and where I saw the phlegm in abundance.

Of this phlegm I have taken some, and laid it on several pieces of thick paper, and dried the same before the fire; and I saw that where it lay very thick, it changed by itself from a clear green into a blackish substance; and where it was quite thin it retained its green colour.

Furthermore I once again examined the so-called burnt paper, and now I saw very distinctly that it was one and the same substance, and of the same composition. For, when I examined this green substance, just I had taken it from the water, through an ordinary microscope, I imagined seeing that these very thin, threadlike parts, which by far exceed a hair in thinness, were round, and that their membrane was very transparent, and that they were filled with a great quantity of green globules of several sizes, the majority of which very nearly the size of about one-sixth of a globule of our blood.

And although I let this green substance or phlegm dry down from the thickness of a little finger, there remained to me, of dry substance, no more than the thickness of a sheet of paper; From which we may deduce how great a quantity of water parts this phlegm contains.

In fact, these green plants, from which the fancied burnt paper came, that was said in Courland to have fallen out of the sky, and my similar, imitation paper from the aforesaid green phlegm, their parts resemble each other so much in all, as if they had been made from one and the same green stuff. For, I could very clearly see, in several threadlike parts of the so-called paper, the joint-like parts, and I often saw, nay, quite a hundred parts lying together that were provided with joints, as is shown here in fig: 1. AB. But I also saw many parts lying together on which I could not observe any joints.

Leeuwenhoek did not often send specimens to the Royal Society, but he sent some of this "paper" along with a less than charitable comment about his contemporaries.

I also enclose herewith a small piece of the imitation (so-called) burnt paper, in order that Your Honours may see what imagination is capable of in some people; and who knows in how many cabinets some of this so-called paper is being preserved as something precious.

This "burnt paper" that Leeuwenhoek enclosed was studied by Brian Ford, who in 1681 recounted the story in context and with great detail. See above in Related sources.

Specimens and methods: maggots in his pocket

For the second letter in a row, Leeuwenhoek mentioned that he used spectacles.

He further told me that he had washed this part in brandy, after extracting it, and had then cut it open, and had seen very many small worms in it. He wanted to show me these worms; but they were so small that I could not recognize them without my spectacles.

Leeuwenhoek fed fresh meat to the maggots in his pocket and showed them to his friends.

I have carried several fly-worms, or maggots, as described heretofore, in a glass tube in my pocket, and fed them every day on fresh meat, and shown them each day to several interested persons, in order that they might witness the rapid growth of the worms; and I brought the latter to their full size in the space of four days, so that I imagine that, in very hot weather, the eggs of a fly will turn into a fly in less than a month's time, and this fly will again lay eggs.

When the worms escaped, he had to look for them with a candle.

Furthermore I fed the worms, or maggots, with fresh meat up to three distinct times, and when on the fifth day - it being the last day of July, in the afternoon - I tried again to give them fresh meat, I saw to my surprise that all the worms or maggots, had crawled out of the box (which I had left slightly open, to give them some air). I looked all over for these worms, but at first I could not find a single one of the same; but when I searched with a candle in the corners and cracks of the ceiling, I found several of these worms, which had been fifty in number.

His garden

Also for the second letter in a row, Leeuwenhoek referred to his garden.

But when I was busy in my garden, cutting few of the early asparagus, I happened to touch, between the vingers of the hand, a very small nettle, which caused me uncommon pain and swelling. ...

In order to show the structure of the nettles' stings, I have put them before the microscope, and handed the same to the draughtsman, that he should draw them just as he might see them.