Hooke's observations

Micrographia: or, Some physiological descriptions of minute bodies made by magnifying glasses title page (left)

illustrations showing Hooke's experimental method accompanying Observ. IX. Of the Colours observable in Muscovy Glass, and other thin Bodies (center) and Observ. X. Of Metalline, and other real Colours (right)

This is Robert Hooke's most influential (and beautiful) book, published when he was 30. The cover not only mentions "the Royal Society" twice, it also has the Society's coat of arms and motto: nullius in verba, on the word of no one. The popularity of the book helped further the Society's image as the most scientifically progressive organization in the world.

For Micrographia, Hooke devised the experiments, often ingeniously given the low-tech means at hand. He developed his own technique for slicing thin sections of a specimen so that he could examine it with his crude illumination system. The book is organized as a series of observations, which is the same Dutch words van Leeuwenhoek used, waaarneming and observatie, eight years later when he began sending letters to the Royal Society.

In addition, Hooke drew all the images himself: a bee's stinger, a razorblade, snow crystals, wood, cork and insects. The originals are copperplate engravings, some of them fold-outs of an already large (folio) volume. These drawings gave the book much of its power.

title page


Observ. LIV. Of a Louse
from Robert Hooke's Micrographia (emphasis added)

This is a Creature so officious, that 'twill be known to every one at one time or other, so busie, and so impudent, that it will be intruding it self in every ones company, and so proud and aspiring withall, that it fears not to trample on the best, and affects nothing so much as a Crown; feeds and lives very high, and that makes it so saucy, as to pull any one by the ears that comes in its way, and will never be quiet till it has drawn blood:

It is troubled at nothing so much as at a man that scratches his head, as knowing that man is plotting and contriving some mischief against it, and that makes it oftentime sculk into some meaner and lower place, and run behind a mans back, though it go very much against the hair; which ill conditions of it having made it better known then trusted, would exempt me from making any further description of it, did not my faithful Mercury, my Microscope, bring me other information of it. ...

It does not seem to have any eye-lids, and therefore perhaps its eyes were so placed, that it might the better cleanse them with its fore-legs; and perhaps this may be the reason, why they so much avoid and run from the light behind them, for being made to live in the shady and dark recesses of the hair., and thence probably their eye having a great aperture, the open and clear light, especially that of the Sun, must needs very much offend them; to secure these eyes from receiving any injury from the hairs through which it passes, it has two horns that grow before it, in the place where one would have thought the eyes should be; each of these CC hath four joynts, which are fringed, as 'twere, with small brisles, from which to the tip of its snout D, the head seems very round and tapering, ending in a very sharp nose D, which seems to have a small hole, and to be the passage through which he sucks the blood.



Observ. XXXIX. Of the Eyes and Head of a Grey drone-Fly, and of several other creatures
from Robert Hooke's Micrographia (emphasis added)

I took a large grey Drone-Fly, that had a large head, but a small and slender body in proportion to it, and cutting off its head, I fix'd it with the forepart or face upwards upon my Object Plate (this I made choice of rather then the head of a great blue Fly, because my enquiry being now about the eyes, I found this Fly to have, first the biggest clusters of eyes in proportion to his head, of any small kind of Fly that I have yet seen, it being somewhat inclining towards the make of the large Dragon-Flies. Next, because there is a greater variety in the knobs or balls of each cluster, then is of any small Fly.) ...

First, that the greatest part of the face, nay, of the head, was nothing else but two large and protuberant bunches, or prominent parts, ABCDEA, the surface of each of which was all cover'd over, or shap'd into a multitude of small Hemispheres, plac'd in a triagonal order, that being the closest and most compacted, and in that order, rang'd over the whole surface of the eye in very lovely rows, between each of which, as is necessary, were left long and regular trenches, the bottoms of every of which, were perfectly intire and not at all perforated or drill'd through.

fly eyes


Observ. XLVII. Of the Shepherd Spider, or long legg'd Spider
from Robert Hooke's Micrographia (emphasis added)

The Carter, Shepherd Spider, or long-legg'd Spider, has, for two particularities, very few similar creatures that I have met with, the first, which is discoverable onely by the Microscope.

Plainly describ'd, is the curious contrivance of his eyes, of which (differing from most other Spiders) he has onely two, and those plac'd upon the top of a small pillar or hillock, rising out of the middle of the top of its back, or rather the crown of its head, for they were fix'd on the very top of this pillar. ... The two eyes, BB, were placed back to back, with the transparent parts, or the pupils, looking towards either side, but somewhat more forward then backwards. ...

The second Peculiarity which is obvious to the eye, is also very remarkable, and that is the prodigious length of its leggs, in proportion to its small round body, each legg of this I drew, being above sixteen times the length of its whole body, ...; the eight leggs are each of them jointed, just like those of a Crab, but every of the parts are spun out prodigiously longer in proportion; each of these leggs are terminated in a small case or shell, shap'd almost like that of a Musle-shell ....

To supply therefore each of these leggs with its proper strength, Nature has allow'd to each a large Chest or Cell, in which is included a very large and strong Muscle, and thereby this little Animal is not onely able to suspend its body upon less then these eight, but to move it very swiftly over the tops of grass and leaves.



Hooke's cork cell

Hooke was the first person to see, and name, the cell, what we now know as the fundamental unit of an organism. (emphasis added)

Observ. XVIII. Of the Schematisme or Texture of Cork, and of the Cells and Pores of some other such frothy Bodies.

"Judging from the lightness and yielding quality of the Cork, that certainly the texture could not be so curious, but that possibly, if I could use some further diligence, I might find it to be discernable with a Microscope, I with the same sharp Penknife, cut off from the former smooth surface an exceeding thin piece of it, and placing it on a black object Plate, because it was it self a white body, and casting the light on it with a deep plano-convex Glass, I could exceeding plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular; yet it was not unlike a Honey-comb in these particulars.

"First, in that it had a very little solid substance, in comparison of the empty cavity that was contain'd between, as does more manifestly Schem. 11.

"Fig. 1. appear by the Figure A and B, for the Interstitia, or walls (as I may so call them) or partitions of those pores were neer as thin in proportion to their pores, as those thin films of Wax in a Honey-comb (which enclose and constitute the sexangular celts) are to theirs.

"Next, in that these pores, or cells, were not very deep, but consisted of a great many little Boxes, separated out of one continued long pore, by certain Diaphragms, as is visible by the Figure B, which represents a sight of those pores split the long-ways.

"I no sooner discern'd these (which were indeed 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) but me thought I had with the discovery of them, presently hinted to me the true and intelligible reason of all the Phænomena of Cork."

cork cell