Philosophical Experiments and Observations

full text available online at Google Books.

On the title page, W. Derham is listed as the Publisher and W. and J. Innys as "Printers to the Royal Society". Today, we would call Derham an editor who provided some introductory material. The book is mostly what Derham calls on the dedication page "this collection of papers", written by Hooke.

The article mentioning Leeuwenhoek begins on p. 257: "Dr. Hooke's Discourse concerning Telescopes and Microscopes; with a short account of their Inventors, read in February 1691-2". The relevant sections are quoted in full on the page "A single votary", referenced below.