A gentleman in Brabant wrote Letter L-308 of sometime in November 1696 to Leeuwenhoek about his long-held Copernican ideas

November 10, 1696

This letter is known only from the extract that Leeuwenhoek included in Letter L-314 of 12 February 1697 to Maarten Etienne van Velden. The gentleman in Brabant wrote that he received Leeuwenhoek's letter on 3 November. Given his enthusiastic response, he may have responded quickly in mid-November.

While the identity of the gentleman in Brabant is not known, this brief passage reveals a little about him.

He went to the university in Paris in the early 1660s, so he was middle-aged when he corresponded with Leeuwenhoek. Collected Letters, vol. 12, speculates that he may be a Jesuit professor. More importantly, he had been a convinced Copernican early in his life.

It is puzzling then that Leeuwenhoek would have sent him a copy of Sesde Vervolg if he didn't think that his ideas would "find much acceptance" and that he turned out to be so wrong.

The "letter on p. 264" of Sesde Vervolg is Letter L-294 of 10 July 1696 to Nicolaas Witsen.


Toward the end of Letter L-314 of 12 February 1697, Collected Letters, vol. 12, Leeuwenhoek writes to Maarten Etienne van Velden:

I cannot omit to tell You that I sent also my latest printed letters to a distinguished and highly learned gentleman in Brabant, with whom I thought my theory would not find much acceptance, but I found I erred in this, for this gentleman greatly commended my theory, and, in order to stop Your adversaries' mouths as well as was possible for my poor capacities, I have thought fit to enclose herewith an extract from said letter. I imagine that you will have shown my theory on the motion of the Earth to your adversaries or perhaps also to others, and if this is so, I shall be extremely obliged to learn from You what they have to say to it,

The extract of the gentleman's letter that Leeuwenhoek added to his own letter:

Your welcome letter of the 30th of October with a book of new observations having been duly handed to me on the 3rd inst., I could not refrain from looking through the index at once, and finding at the top noted the letter on p. 264, in which You deal with the daily rotation of the Earth, which I assumed for certain 35 years ago (as the easiest and most comprehensible way in which the whole system of the planets and the firmament can move in perfect time in relation to the circumference of their orbit), I was highly satisfied to find the proof of a matter which I had never yet considered, to wit why the clouds and everything arising from the earth rises so high above it, which I thought to be due only to the heat of the sun or the subterranean fires which cause them to rise from the earth.

Now you teach me that the rotation of the earth itself causes them to move away, and you confine yourself to this, and that the sun heating the air only makes it suited to cause the clouds to reach a greater height than if the air is very cold.

When in 1661 I was in Paris, I there found in our College all the various world systems of Ptolemy, Tycho Brahe, and Copernicus, each rotating in its own way so that in half an hour one could see the general rotation of each of them; but none pleased me better than the Halsey-Copernicus system, where the earth, remaining in the centre of the creations, rotated daily as it were about its axis, the planets further moving in their orbits, the moon in a month, the sun in a year, etc. Otherwise they would all have to move daily in 24 hours at an incredible rate from East to West. Through your observation I am now strengthened in my opinion, considering the further convenience which such a rotation of the earth provides. May the Lord protect You for many years to come, etc.