At age 40, first letter published in Philosophical Transactions

May 19, 1673

Oldenburg translated Leeuwenhoek's first letter. It was read at the regular meeting of the Royal Society on May 7. Oldenburg published part of it in number 94 of Philosophical Transactions, dated May 19, 1673. The ten figures and their explanations were published the following fall.

Hardly any articles about microscopes had appeared in Philosophical Transactions since Robert Hooke moved on to other interests after the big splash made by his book Micrographia. Perhaps Oldenburg wanted to get Leeuwenhoek's observations into print as soon as possible.

2 articles. Collected Letters counts it as one letter. Fournier counts it as two letters.