Structure of the letters in Period 2

The 25 letters that Leeuwenhoek numbered and self-published from 1679 to 1687 (Period 2) have similar structure. On the right (click to enlarge) is the first page of the printed version of Letter 43 of January 5, 1685 (AB 82) to Members of the Royal Society. It was, as were all of Leeuwenhoek's self-published letters, preceded by a summary that was not in the manuscript and thus not in any of the volumes of Alle de Brieven / Collected Letters.

The 29 unnumbered letters share some of these structural features.

All 54 letters had openings and closings of the conventional formal nature common to the Seventeenth Century. They were not usually printed with the extract in Philosophical Transactions, but Leeuwenhoek always included them in his self-published volumes. For example, the letter of October 30, 1686, to Antonio Magliabechi began:

Most Illustrious, Highly Learned and Very Renowned Sir

The letter of May 13, 1680, to the members of the Royal Society ended:

The body of every letter referred to, described, and discussed the specimens that Leeuwenhoek observed, many illustrated with figures. In the process, he sometimes noted the source of his specimens and the methods he used to study them.

Before, after, and in between his observations, Leeuwenhoek wove a number of other topics that fall into four types, shown in the box on the right. An individual letter may or may not address them, so the table below shows which letters included information of each type.

The columns on Leeuwenhoek's response to other researchers and their books and to the public make it clear. Far from being a solitary genius, Leeuwenhoek was part of a network of other scholars and interested members of the public, some of whom visited his house and only some of whom he mentioned in his letters. Along with dozens of other researchers who used empirical methods and exchanged information in the form of letters, Leeuwenhoek was a participant in what even then was called the Republic of Letters. Their research responded to his and his research responded to theirs.

Leeuwenhoek was also concerned with how his observations contradicted or confirmed what most people thought. The column on calculations shows Leeuwenhoek's awareness of the difficulty people had accepting the minute sizes and innumerable quantities he reported in his letters.

Key to the table

The letters themselves had no headings or subheadings; the column headings on the table below did not appear in the letters themselves. Nor did the contents of the table cells unless enclosed in quotation marks. The quotations give a sense of the text. A blank cell indicates that the letter did not address that topic.

For more on each letter's content, see the page for that letter below under Learn more or the pull-down menu at the top of the right sidebar.