Period 7 - 1720-1723

Leeuwenhoek not only survived through the lean years when Edmond Halley was editor. He kept living -- and reporting his observations -- until he was 91. This gave him the opportunity to enjoy a couple of years at the end of his life when he was again published regularly in London.

The information on this page refers only to Cole's list of the letters because Alle de Brieven / Collected Letters has not published past 1707. Leeuwenhoek didn't number them, so Cole continued the Roman numeral sequence from the Send-Brieven. These letters were [XLVII] through [LXI].

The table below summarizes the final four years of Leeuwenhoek's scientific career, through the end of the year after his death in August 1723. James Jurin was the editor of Philosophical Transactions.

Letters in Period 7

For volume 31, Halley was replaced as editor by James Jurin, who shifted the direction of Philosophical Transactions. The position of secretary continued to have stability at the end of Newton's long tenure as president. Jurin and the astronomer and mathematician John Machin were the two secretaries through this period.

It wasn't until mid-century, 1753, that Philosophical Transactions finally became an official publication of the Society, as opposed to the personal project and sole responsibility of Henry Oldenburg and the half-dozen fellows who followed him as editor and secretary.

In the ongoing struggle between the physical sciences and the biological sciences, Jurin was with the former, as, of course, were Machin and the Society's president during this period, Isaac Newton.

In 1726, Jurin wrote about Newton in the final volume of Philosophical Transactions that he edited (italics in original):

Jurin was not, however, as focused as Halley. And Leeuwenhoek wasn't claiming royalty; he just wanted to get his observations published.

Leeuwenhoek's final fifteen letters, as listed by Cole, were all published in volumes 31 and 32. This included the final two, dictated on his death bed in August 1723 to Johan Hoogvliet and translated into Latin before Hoogvliet sent them. Jurin published them the following year, in Latin.

In Delft

After the Send-Brieven / Epistles of 1718, Leeuwenhoek published no more volumes on his own. Of the final fifteen letters that he wrote to the Royal Society, half of them were translated into Latin before he sent them, including the final five.

As with the Send-Brieven / Epistles, the elderly Leeuwenhoek was not looking at things that needed the strongest lens, or we presume, the strongest eyes. They were almost all sections or otherwise flattened on glass presumably so that he could use transmitted light passing through the specimen.

From the titles of the articles in Philosophical Transactions, Leeuwenhoek studied:

• bones and periosteum
• seeds of plants
• vessels in several sorts of wood
• calluses on the hands and feet
• foetus and reproductive organs of a sheep
• magnetic quality of iron
• muscular fibres of different animals and fish
• particles of fat (image on the right)
• membranes enclosing the fasciculi of fibres

Dual Thrones

The concerns expressed by Newton and Jurin above were not resolved at the Royal Society until 1887, when Philosophical Transactions was split into two parts, A and B.

According to the Royal Society Publishing web site, Philosophical Transactions A is devoted to a specific area of the mathematical, physical and engineering sciences, the Newton / Halley faction.

Astronomy and astrophysics
Chemistry
Earth Sciences

Philosophical Transactions B is divided into four cluster areas:

Cell and Development
Health and Disease
Environment and Evolution
Neuroscience and Cognition

Leeuwenhoek made substantial foundational contributions in half of those areas.