Micrographia, by Robert Hooke

Table of Contents

To the King.

To the Royal Society

The Preface

Observations:

  1. Of the Point of a sharp small Needle.

    A Description of it: what other Bodies have the sharpest points: of the ruggedness of polisht Metal. A description of a printed point. Of very small writing, and the use of it for secret intelligence: the cause of the coursness of printed lines and points.

  2. Of the Edge of a Razor.

    A description of it: the causes of its roughness: of the roughness of very well polisht Optick Glasses..

  3. Of fine Lawn, or Linnen Cloth.

    A description of it: A silken Flax mention'd, an attempt to explicate the Phænomena of it, with a conjecture at the cause of the gloss of Silk.

  4. Of fine waled Silk, or Taffety.

    A short description of it. A conjecture about the reason why Silk is so susceptible of vivid colours: and why Flax and Hair is not. A conjecture, that it way perhaps be possible to spin a kind of artificial Silk, out of some glutinous substance that may equalize natural Silk.

  5. Of watered Silks, or Stuffs.

    The great unaccurateness of artificial works. A description of a piece of water'd Silk; an Explication of the cause of the Phænomena: the way by which that operation is perform'd: some other Phænomena mention'd depending on the same cause.

  6. Of Small Glass Canes.

    The exceeding smallness of some of these Bodies. By what means the hollowness of these small pipes was discover'd: several Phænomena of it mention'd. An attempt to explicate them from the congruity and incongruity of Bodies: what those proprieties are. A hypothetical explication of fluidity: of the fluidity of the air, and several other Phænomena of it: of congruity & incongruity; illustrated with several Experiments: what effects may be ascrib'd to these properties: an explication of the roundness of the surface of fluid Bodies: how the ingress of fluid bodies into a small hole of an heterogenious body is hindred by incongruity; a multitude of Phænomena explicable hereby. Several Quæries propounded; 1. Concerning the propagation of light through differing mediums. 2. Concerning Gravity. 3. Concerning the roundness of the Sun, Moon, and Planets. 4. Concerning the roundness of Fruits, Stones, and divers artificial Bodies. His Highness Prince Rupert's way of making Shot. Of the roundness of Hail. Of the grain of Kettering Stone, and of the Sparks of fire. 5. Concerning springiness and tenacity. 6. Concerning the original of Fountains; several Histories and Experiments relating thereto. 7. Concerning the dissolution of Bodies in Liquors. 8. Concerning the universality of this Principle: what method was taken in making and applying experiments. The explication of filtration, and several other Phænomena; such as the motion of Bodies on the surface of Liquors; several Experiments mention'd to this purpose. Of the height to which the water may rise in these Pipes; and a conjecture about the juices of Vegetables, & the use of their pores. A further explication of Congruity: And an attempt of solving the Phænomena of the strange Experiment of the suspension of the Mercury at a much greater height then thirty inches. The efficacy of immediate contact, and the reason of it.

  7. Of some Phænomena of Glass drops.

    Several Experiments made with these small Bodies. The manner of the breaking and flawing of them, explicated by Figures. What other bodies will be flawed much in the same manner: so other tryals, and a description of the Drops themselves: some conjectures at the cause of the Phænomena, indeavoured to be made probable by several Arguments and Experiments. An Experiment of the expansion of Water by heat, and shrinking by cold: the like Proprieties suppos'd in Glass drops, and what effects proceed from them: the seven Propositions on which the conjectures are grounded. Experiments to shew, that bodies expand by heat. The manner of making Thermometers, and the Instrument for graduating them. The manner of graduating them, and their use: Other Experiments to prove the expansion of bodies by heat. Four experimental Arguments to prove the expansion of Glass by heat: further prov'd by the Experiment of boyling Alabaster; which is explicated. An explication of the contracting of heated Glass upon cooling. An explication how the parts of the Glass become bent by sudden cold, and how kept from extricating themselves by the contignation of the Glass drop; which is further explicated by another Experiment made with a hollow Glass ball: the reason of the flying asunder of the parts further explicated: that 'tis probable these bodies may have many flaws, though not visible, and why: how a gradual heating and cooling does put the parts of Glass, and other hardned bodies, into a looser texture.

  8. Of the fiery Sparks struck from a Flint or Steel.

    The occasion and manner of making this Experiment: divers Observations set down in order to the finding out the reasons: some conjectures concerning it, which are endeavoured to be explicated and confirm'd by several Experiments and Reasons: the Hypothesis a little further explicated. Some Observations about the Globular Figure: and an Experiment of reducing the filings of Tin or Lead to exactly round Globules.

  9. Of Fantastical Colours.

    The texture of Muscovy Glass; its Figures: what other Bodies are like it: that it exhibits several colours, and how: several Observations and Experiments about those colours: the reason why on this occasion the nature of colours is inquir'd into. A conjecture at the reason of these colours explicated by several Experiments and Reasons: First, by continual cleaving the Body till it become colour'd. Secondly, by producing all kinds of colours with two flat Plates of Glass. Thirdly, by blowing Glass so thin in the Lamp, till it produce the same effect. Fourthly, by doing the same with Bubbles of divers other transparent Bodies: the reasons of the colours on nealed Steel, where by the way the causes of the hardning and tempering of Steel, endeavour'd to be shewn and explicated by several Reasons and Experiments: the reason of the colours on Lead, Brass, Copper, Silver, &c. other Instances of such colour'd bodies in animal substances: several other distinguishing Observations. Des Cartes Hypothesis of Colours examin'd. An Hypothesis for the explication of light by motion, indeavoured to be explicated and determined by several Reasons and Experiments: three distinguishing Properties of the motion of light. The distinguishing Properties of a trasparent Medium [that there seems to be no Experiment that proves the Instantaneous motion of light] the manner of the propagation of light through them. Of the homogeniety and heterogeniety of transparent Mediums, and what effects they cause on the Rayes of light, explicated by a Figure: an Examination of the refraction of the Rays by a plain Surface, which causes Colours. An Examination of the like effects produced by a spherical Surface: the use that may be made of these Experiments, for the examination of several Hypotheses of Colours. Des Cartes Hypothesis examin'd. Some Difficulties taken notice of in it. What seems most likely to be the cause of colour: that propriety is indeavoured to be shewn in a Glass ball: that the reflection is not necessary to produce Colours nor a double refraction: the Hypothesis further examined, both in the pellucid Medium and in the Eye. The definitions of Colours; and a further explication and examination of the Proprieties of laminated Bodies; by what means they conduce to the production of Colours.

  10. Of Metalline, and other real Colours.

    That all Colours seem to be caus'd by refraction. An Hypothesis consonant hereunto, explicated by Figures. How several Experiments, of the sudden changing of Colours by Chymical Liquors may be hereby explicated: how many wayes such Chymical Liquors may alter the colours of Bodies. Objections made against this Hypothesis of two colours only, indeavoured to be answer'd, by several Reasons and Experiments. The reason why some Colours are capable of being diluted, others not: what those are: that probably the particles of most metalline Colours are transparent; for this several Arguments and Observations are recited: how Colours become incapable of diluting, explicated by a Similitude. An Instrument, by which one and the same coloured Liquor at once exhibited all the degrees of colours between the palest yellow and deepest red: as likewise another that exhibited all varieties of blues: several Experiments try'd with these Boxes. An Objection drawn from the nature of Painters colours answered: that diluting and whitening a colour are different operations; as are deepening and blackening: why some may be diluted by grinding, and some other by being tempered with Oyl: several Experiments for the explicating of some former Assertions: why Painters are forced to make use of many colours: what those colours are: and how mixt. The conclusion, that most coloured Bodies seem to consist of transparent particles: that all colours dissoluble in Liquors are capable of diluting: some of mixing, what a strange variety may thereby be produc'd.

  11. Of Figures observ'd in small Sand.

    Of the substances and shapes of common and other Sands: a description of a very small Shell.

  12. Of Gravel in Urine.

    A description of such Gravel, and some tryals made with it, and conjectures at its cause.

  13. Of the small Diamants, or Sparks in Flints.

    A description and examination of some of them, explicated further by Cornish Diamonds: several Observations about reflection and refraction: and some deductions therefrom; as an explication of whiteness; that the Air has a stronger reflection then Water. How several Bodies may be made transparent: an explication of the Phænomena of Oculus Mundi. Of the regular Geometrical Figures of several Bodies: an hypothetical explication mentioned: the method of prosecuting this inquiry.

  14. Of several kindes of frozen Figures.

    The Figures of hoar Frost, and the Vortices on windows: several Observations on the branched Figures of Urine: the Figures of Regulus Martis stellatus, and of Fern. Of the Figures of Snow. Of frozen water.

  15. Of Kettering-stone, and of the pores of Inanimatebodies.

    A description of the Figure of the Particles, and of the Pores, and of the Contexture. Several Observations and Considerations thereupon: some Conjectures about the medium and propagation of light, and the constitution of fluid and transparent Bodies. Several Experiments to prove the porousness of Marble, and some other Stones. An account of some Experiments to this purpose made on an Oculus Mundi: some other Considerations and Experiments about the porousness of Bodies: some other Considerations about the propagation of light and refraction.

  16. Of Charcoal, or burnt Vegetables.

    Of two sort of Pores to be found in all Woods and Vegetables; the shape of them; the number, thickness, manner and use of these Pores. An explication of the Phænomena of Coals. The manner of charring Wood, or any other body. What part of Wood is combustible. An Hypothesis of fire explicated in twelve particulars, wherein the Action of the Air, as a Menstruum in the dissolution of all sulphureous bodies, is very particularly explicated, and some other Considerations about the Air proposed: the examination of a piece of Lignum fossile sent from Rome, and some Conclusions thence deduc'd.

  17. Of Petrify'd wood, and other Petrify'd bodies.

    Several Observations of divers kinds of these substances. A more particular examination and explication of one very notable piece of petrified Wood; and some Conjectures about the cause of those productions: several Observations made on other petrified Bodies, as shells, &c. And some probable Conclusions thence deduc'd, about the original cause of those Bodies.

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

    Several Observations and Considerations about the nature of Cork: the number of Pores in a cubical Inch, and several considerations about Pores. Several Experiments and Observations about the nature of Cork: the Texture and Pores of the Pith of an Elder, and several other Trees: of the Stales of Burdocks, Teasels, Daisies, Carret, Fennel, Ferne, Reeds, &c. of the frothy texture of the Pith of a Feather: some Conjectures about the probability of values in these Pores. Argued also from the Phænomena of sensible and humble Plant: some Observations on which are inserted.

  19. Of a Plant growing in the blighted or yellow specks of Damask-rose-leaves, Bramble-leaves, and some other kind of leaves.

    Several Observations and Examinations made of them: several Considerations about spontaneous generation arising from the putrefaction of Bodies.

  20. Of blue Mould, and of the first Principles of Vegetation arising from Putrefaction.

    The description of several kinds of Moulds. The method of proceeding in natural Inquiries. Several Considerations about the nature of Mould and Mushromes. 1. That they may be produc'd without seed. 2. That they seem to have none. 3. That Salts, &c. are shap'd into as curious figures without a seed. 4. Of a kind of Mushrome growing in a Candle: A more particular explication of this last sort of Mushromes. 5. Of the figure and manner of the production of petrified Iceicles: several deductions from these Considerations, about the nature of the vegetation of Mould and Mushromes.

  21. Of Moss, and several other small-vegetative Substances.

    The description of several sorts of Mosses; upon this occasion several Conjectures, about the manner of the production of these kinds of Bodies, are hinted, and some of them explicated by a Similitude taken from a piece of Clock-work, The vast difference of the bigness of vegetable Bodies; and the probability that the least may comprehend as curious contrivances as the greatest. Of multitudes of other Moulds, Mosses, and Mushromes, and other vegetating Principles, in Water, Wood, &c.

  22. Of common Sponges, and several other Spongiefibrous bodies.

    Observ. 22. Of Sponges, and other fibrous Bodies.

    Several Observations and Conjectures about the making of these Bodies, and several Histories out of Authors. Scarce any other Body hath such a texture; the fibrous texture of Leather, Spunk, &c. (which are there describ'd) come nearest to it That upon tryal with a piece of Spunge and Oyl the necessity of respiration could not be alter'd.

  23. Of the curious texture of Sea-weeds.

    From the curiously shap'd Surface of this Sea-weed, and some others, is conjectured the possibility of Multitudes of the like.

  24. Of the surfaces of Rosemary, and other leaves.

    The description, 1. Of the bald Surfaces of Leaves. 2. Of the downy Surfaces of several others. 3. Of the gummous exsudation, or small transparent Pearls, discovered with a Microscope in several others. An Instance of all which is afforded in a Rosemary Leaf.

  25. Of the stinging points and juice of Nettles, and some other venomous Plants.

    A description of the Needles and several other contrivances in the leaf of a Nettle: how the stinging pain is created: upon this several considerations about poysoning Darts are set down. An Experiment of killing Effs, and Fishes with Salt. Some conjectures at the efficacy of Baths; the use that may be made of injecting into the Veins. A very remarkable History out of Bellonius; and some Considerations about staining and dying of Bodies.

  26. Of Cowage, and the itching operation of some bodies.

    The definition of it out of Parkinson: an Experiment made of it: a description, and some conjectures at the cause of the Phænomena.

  27. Of the Beard of a wilde Oat

    The description of its shape and properties: the manner of making a Hygroscope with it; and a Conjecture at the causes of these motions, and of the motions of the Muscles.

  28. Of the Seeds of Venus looking-glass, or CornViolet.

    The description of them.

  29. Of the Seeds of Tyme.

    A description of them. A digression about Natures method.

  30. Of the Seeds of Poppy.

    The description and use of them.

  31. Of Purslane-seed.

    A description of these and many other Seeds.

  32. Of the Figure of several sorts of Hair, and of the texture of the skin.

    The description of several sorts of Hair; their Figures and Textures: the reason of their colours, A description of the texture of the skin, and of Spunk and Sponges: by what passages and pores of the skin transpiration seems to be made. Experiments to prove the porousness of the skin of Vegetables.

  33. Of the Scales of a Soal, and other Fishes.

    A description of their beauteous form.

  34. Of the Sting of a Bee.

    A description of its shape, mechanisme, and use.

  35. Of the contexture and shape of the particles of Feathers.

    A description of the shape and curious contexture of Feathers: and some conjectures thereupon.

  36. Of Peacoks, Ducks, and other Feathers of changeable colours.

    A description of their curious form and proprieties; with a conjecture at the cause of their variable colours.

  37. Of the Feet of Flyes, and several other Insects.

    A description of their figure, parts, and use; and some considerations thereupon.

  38. Of the Structure and motion of the Wings of Flies.

    After what manner and how swiftly the wings of Insects move. A description of the Pendulums under the wings, and their motion; the shape and structure of the parts of the wing.

  39. Of the Eyes and Head of a Grey drone-Fly, and of several other creatures.

    1. All the face of a Drone-fly is nothing almost but eyes. 2. Those are of two magnitudes. 3. They are Hemispheres, and very reflective and smooth. 4. Some directed towards every quarter. 5. How the fly cleanses them. 6. Their number. 7. Their order: divers particulars observ'd in the dissecting a head. That these are very probably the eyes of the Creature; argued from several Observations and Experiments, that Crabs, Lobsters, Shrimps, seem to be water Insects, and to be framed much like Air Insects. Several Considerations about their manner of vision.

  40. Of the Teeth of a Snail.

    A brief description of it.

  41. Of the Eggs of Silk-worms, and other Insects.

    Several Observables about the Eggs of Insects.

  42. Of a blue Fly.

    A description of its outward and inward parts. Its hardiness to indure freezing, and sleeping in Spirit of wine.

  43. Of the Water-Insect or Gnat.

    A description of its shape, transparency, motion, both internal and progressive, and transformation. A History somewhat Analogus cited out of Piso. Several Observations about the various wayes of the generations of Insects: by what means they act so seemingly wisely and prudently. Several Quæries propounded. Postscript, containing a relation of another very odd way of the generation of Insects. An Observation about the fertility of the Earth of our Climate in producing Insects, and of divers other wayes of their generation.

  44. Of the tufted or Brush-horn'd Gnat.

    Several Observables about Insects, and a more particular description the parts of this Gnat.

  45. Of the great Belly'd Gnat or female Gnat.

    A short description of it.

  46. Of the white featherwing'd Moth or Tinea Argentea.

    A description of the feathers and wings of this, and several other Insects. Divers Considerations about the wings, and the flying of Insects and Birds.

  47. Of the Shepherd Spider, or long legg'd Spider.

    A description of its Eyes: and the sockets of its long legs: and a Conjecture of the mechanical reason of its fabrick; together with a supposition, that 'tis not unlikely, but Spiders may have the make of their inward parts exactly like a Crab, which may be call'd a water Spider.

  48. Of the hunting Spider, and several other sorts of Spiders.

    A short description of it; to which is annext an excellent History of it, made by Mr. Evelyn. Some further Observations on other Spiders, and their Webs, together with an examination of a white Substance flying up and down in the Air after a Fog.

  49. Of an Ant or Pismire.

    That all small Bodies, both Vegetable and Animal, do quickly dry and wither. The best remedy I found to hinder it, and to make the Animal lye still to be observ'd. Several particulars related of the actions of this Creature and a short description of its parts.

  50. Of the wandring Mite.

    A description of this Creature, and of another very small one, which usually bore it company. A Conjecture at the original of Mites.

  51. Of the Crab-like Insect.

    A brief description of it.

  52. Of the small Silver-colour'd Book-worm.

    A description of it; where by the way is inserted a digression, experimentally explicating the Phænomena of Pearl. A consideration of its digestive faculty.

  53. Of a Flea.

    A short description of it.

  54. Of a Louse.

    A description of its parts, and some notable circumstances.

  55. Of Mites.

    The exceeding smalness of some Mites, and their Eggs. A description of the Mites of Cheese: and an intimation of the variety of forms in other Mites, with a Conjecture at the reason.

  56. Of a small Creature hatch'd on a Vine.

    A description of them; a ghess at their original; their exceeding smalness compar'd with that of a Wood-louse, from which they may be suppos'd to come.

  57. Of the Eels in Vinegar.

    A description of them, with some considerations on their motions.

  58. Of the Inflexion of the Rays of Light in the Air.

    A short rehearsal of several Phænomena. An attempt to explicate them: the supposition founded on two Propositions, both which are indeavoured to be made out by several Experiments, What density and rarity is in respect of refraction: the refraction of Spirit of Wine compared with that of common Water: the refraction of Ice. An Experiment of making an Undulation of the Rays by the mixing of Liquors of differing density. The explication of inflection, mechanically and hypothetically: what Bodies have such an inflection. Several Experiments to shew that the Air has this propriety; that it proceeds from the differing density of the Air: that the upper and under part of the Air are of differing density: some Experiments to prove this. A Table of the strength of the spring of the Air, answering to each degree of extension; when first made, and when repeated. Another Experiment of compressing the Air. A Table of the strength of the Air, answering to each compression and expansion; from which the height of the Air may be suppos'd indefinite; to what degree the Air is rarifi'd at any distance above the Surface of the Earth: how, from this, Inflection is inferr'd; and several Phænomena explain'd. That the Air near the Earth is compos'd of parts of differing density; made probable by several Experiments and Observations; how this propriety produces the effects of the waving and dancing of Bodies; and of the twinkling of the Stars. Several Phænomena explicated. Some Quæries added.

    1. Whether this Principle may not be made use of, for perfecting Optick Glasses? What might be hoped from it if it were to be done?

    2. Whether from this Principle the apparition of some new Stars may not be explicated?

    3. Whether the height of the Air may be defin'd by it?

    4. Whether there may not sometimes be so great a disparity of density between the upper and under parts of the Air, as to make a reflecting Surface?

    5. Whether, if so, this will not explicate the Phænomena of the Clouds. An Experiment to this purpose?

    7. Whether the Rayes from the top of Mountains are not bended into Curve-lines by inflection? An Argument for it, taken from an Experiment made on St. Paul's Steeple.

    8. Whether the distance of the Planets will not be more difficult to be found? What wayes are most likely to rectifie the distance of the Moon: the way of fitting Telescopes for such Observations. How to make the Observations, and how from them to find the true distance of the Moon at any time. How the distance of the Sun may be found by two Observators. The way by the Dicotomy of the Moon uncertain. That the distance of the Moon may be less then it has been hitherto suppos'd. Kepler's Supposition not so probable: the explication of the Phænomena by another Hypothesis.

  59. Of the fixt Stars.

    Of the multitudes of Stars discoverable by the Telescope, and the variety of their magnitudes: 78. Stars distinguisht in the Pleiades: that there are degrees of bigness even in the Stars accounted of the same magnitude: the longer the Glasses are, and the bigger apertures they will indure, the more fit they are for these discoveries: that 'tis probable, longer Glasses would yet make greater discoveries. 5. Stars discover'd in the Galaxie of Orion's Sword.

  60. Of the Moon.

    A description of a Vale in the Moon; what call'd by Hevelius and Ricciolus, and how describ'd by them: with what substances the hills of the Moon may be cover'd. A description of the pits of the Moon, and a conjecture at their cause: two Experiments that make it probable, that of the surface of boyl'd Alabaster dust seeming the most likely to be resembled by eruptions of vapours out of the body of the Moon: that Earthquakes seem to be generated much the same way, and their effects seem very similar. An Argument that there may be such variations in the Moon, because greater have been observ'd in the Sun: because substance of the Moon and Earth seem much alike: and because 'tis probable the Moon has a gravitating principle: this is argued from several particulars. The reason why several pits are one within another. The use that may be made of this Instance of a gravity in the Moon.

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