Micrographia

Micrographia is a book by the English natural philosopher Robert Hooke, published in London in 1665 by the Royal Society's printers. Its full title is Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses, with Observations and Inquiries thereupon. It has sixty numbered observations and thirty-eight engraved plates, which the text calls "Schemes". Most of the observations describe objects seen through a compound microscope, from the point of a needle to a louse, and the last two turn a telescope on the stars and the Moon.^[1]

Two passages are quoted more often than any other. One is the flea, which has a plate to itself. The other is the slice of cork whose cavities Hooke called "pores, or cells".^[1]

The Royal Society's order for the printing is dated November 23, 1664 and signed by Brouncker as the Society's president. It describes Hooke as a Fellow of the Society and appoints John Martyn and James Allestry as its printers.^[1] The title page reads 1665. On January 20 of that year Samuel Pepys fetched a copy from his bookseller, "a most excellent piece, and of which I am very proud". On the evening of January 21 he sat up in his chamber until two o'clock reading it, and he wrote of "the most ingenious book that ever I read in my life".^[2][3]

In the preface Hooke argues that "artificial Instruments and methods" can correct "the Sense, the Memory, and Reason". On the way he promises a method of finding longitude "very speedily", and remarks that human flight fails only for want of strength in human muscles.^[1]

Observation I is the point of a needle. Hooke begins there because natural history, like geometry, should start from a point. To the naked eye the tip is "very sharp", but under a good microscope it "appears a broad, blunt, and very irregular end". The razor in Observation II has an edge that he found "to be of all kind of shapes, except what it should be". Linen, silk, charcoal and blue mold follow, then fish scales, the sting of a bee and the eye of a drone-fly.^[1] The flea is Observation LIII, introduced with the sentence "The strength and beauty of this small creature, had it no other relation at all to man, would deserve a description." The louse that follows is "so officious, that 'twill be known to every one at one time or other", and it "affects nothing so much as a Crown".^[1]

Observation XVIII concerns cork. Hooke cut a thin piece with a pen-knife "sharpen'd as keen as a Razor", set it on a black plate, lit it from above through a plano-convex lens, and saw that it was "all perforated and porous, much like a Honey-comb". The openings were irregular, and the walls between them were thin. He wrote that these were "the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this". Thin partitions divided them into little boxes, which he called "Cells".^[1]

The cells were for Hooke the reason that cork is light, floats and stops a bottle: the air is shut into separate boxes that neither water nor more air can enter. Then he counted. About sixty cells stood end to end in an eighteenth of an inch, which made a thousand or so to the inch, "above a Million" to the square inch and "above twelve hundred Millions" to the cubic inch. His figures, 1,166,400 and 1,259,712,000, are the second and third powers of 1,080, which is sixty multiplied by eighteen. He called the result "a thing almost incredible, did not our Microscope assure us of it by ocular demonstration".^[1]

The cells were the dead walls of plant tissue. Hooke did not take them for the units of living things, and that idea came more than 170 years later with the cell theory of Matthias Schleiden and Theodor Schwann in 1838 and 1839.^[4][5] The name he gave them stayed.

Observation LIX concerns the multitudes of small stars that a telescope reveals. The last, "Of the Moon", exists because the plate of the stars had "a pretty large corner" left empty, and Hooke added a small specimen of the Moon "for the filling it up".^[1]

The book appeared eight years before the first of the letters from Antonie van Leeuwenhoek was printed in the Royal Society's Philosophical Transactions, and it belongs at the start of the History of the microscope. Observation I is of a needle. In 1948 the first aperture of the Coulter counter was a hole that Wallace H. Coulter burned in cellophane with a heated needle.^[6]

• History of the microscope
• Antonie van Leeuwenhoek
• Coulter counter
• Single-molecule biophysics