September 1665

Micrographia

Publication of Robert Hooke's Micrographia in London

Pepys found the new book at his binder on 2 January, well before its supposed September publication, and ordered a copy on the spot.

January 1665, not September

The Royal Society-authorized Micrographia reached London's book trade in January 1665. Samuel Pepys saw a copy at his bookseller's binder on 2 January and received his own on 20 January, which rules out the September date the calendar carries.

On 21 January he stayed up until 2 a.m. reading it, and recorded that it was the most ingenious book he had ever read.

Observation XVIII

In Observation XVIII, Hooke described a very thin slice of cork as porous like a honeycomb and called its compartments 'pores, or cells' — the word's introduction into a biological context. His own comparisons are honeycomb cells, little boxes, and bubbles; the familiar monastery-room explanation is not what the passage says.

He estimated about 1,166,400 compartments per square inch, and 1,259,712,000 per cubic inch. What he pictured and described were the empty walls and cavities of dead cork tissue, not living cells with visible internal structures.

A folio you had to unfold

The first edition ran to 246 numbered pages, ten unnumbered pages, and 38 engraved plates, some of them folded, carrying sixty observations in all. The Royal Society describes its own copy's louse plate as unfolding to nearly twice the size of the book.

The Society's council had ordered the work printed, and its president William Brouncker authorized the imprimatur on 23 November 1664. John Martyn and James Allestry printed it as printers to the Royal Society.

Sources

Researched 24 Aug 2026 8 sources not yet audited Date corrected

How this was checked

Researched from the web into a fact sheet and rewritten from that sheet. This article has not yet had an independent model audit. How the pipeline works →

Date corrected. The research places this at 1665-01.

What the sources leave uncertain

No consulted primary bibliographical record fixes a single publication day, but copies were already at a London binder by 2 January 1665. January is therefore secure; September is not.
Hooke said these were perhaps the first microscopic pores ever seen because he knew of no earlier report. That is Hooke’s priority claim, not independent proof that nobody had observed them.
Hooke’s text compares the structures explicitly with honeycomb cells, little boxes and bubbles. The familiar monastery-room explanation is a plausible etymological gloss but is not the explanation he states in Observation XVIII.