Wrote Letter L-193 of 1687-10-17 to members of the Royal Society about amber, 'burned paper' from the sky, rotifers, maggots, blow flies, the stinging hairs of nettles, and the East-Indian centipede

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.