Micrographia by Robert Hooke

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But this was onely the Figure of the _Bearded hoar-frost_; and as for the
particles of other kinds of _hoar-frosts_, they seem'd for the most part
irregular, or of no certain Figure. Nay, the parts of those curious
branchings, or _vortices_, that usually in cold weather tarnish the surface
of Glass, appear through the _Microscope_ very rude and unshapen, as do
most other kinds of frozen _Figures_, which to the naked eye seem exceeding
neat and curious, such as the Figures of _Snow_, frozen _Urine_, _Hail_,
several _Figures_ frozen in common Water, &c. Some Observations of each of
which I shall hereunto annex, because if well consider'd and examin'd, they
may, perhaps, prove very instructive for the finding out of what I have
endeavoured in the preceding Observation to shew, to be (next the _Globular
Figure_ which is caus'd by _congruity_, as I hope I have made probable in
the sixth _Observation_) the most simple and plain operation of Nature, of
which, notwithstanding we are yet ignorant.

I.

_Several Observables in the _six-branched_ Figures form'd on the surface of
Urine by freezing._

1 [11]The Figures were all frozen almost even with the surface of the
_Urine_ in the Vessel; but the bigger stems were a little _prominent_ above
that surface, and the parts of those stems which were nearest the center
(a) were biggest above the surface.

2 I have observ'd several kinds of these Figures, some smaller, no bigger
then a Two-pence, others so bigg, that I have by measure found one of its
stems or branches above four foot long; and of these, some were pretty
round, having all their branches pretty neer alike; other of them were more
extended towards one side, as usually those very large ones were, which I
have observ'd in Ditches which have been full of foul water.

3 None of all these Figures I have yet taken notice of, had any regular
position in respect of one another, or of the sides of the Vessel; nor did
I find any of them equally to exactness extended every way from the center
a.

4 Where ever there was a center, the branchings from it, ab, ac, ad, ae,
af, ag, were never fewer, or more then six, which usually concurr'd, or met
one another very neer in the same point or center, a; though oftentimes not
exactly; and were enclin'd to each other by an angle, of very near sixty
degrees, I say, very neer, because, though having endeavoured to measure
them the most acurately I was able, with the largest Compasses I had, I
could not find any sensible variation from that measure, yet the whole
six-branched Figure seeming to compose a solid angle, they must necessarily
be somewhat less.

5 The middle lines or stems of these branches, ab, ac, ad, ae, af, ag,
seem'd somewhat whiter, and a little higher then any of the _intermediate_
branchings of these Figures; and the center a, was the most _prominent_
part of the whole Figure, seeming the _apex_ of a solid angle or _pyramid_,
each of the six plains being a little enclin'd below the surface of the
_Urin_.

6 The lateral branchings issuing out of the great ones, such as op, mq, &c.
were each of them inclin'd to the great ones, by the same angle of about
sixty degrees, as the great ones were one to another, and always the bigger
branchings were _prominent_ above the less, and the less above the least,
by proportionate _gradations_.

7 The _lateral_ branches shooting out of the great ones, went all of them
from the center, and each of them was parallel to that great branch, next
to which it lay; so that as all the branches on one side were parallel to
one another, so were they all of them to the _approximate_ great branch, as
po, qr, as they were parallel to each other, and shot from the center, so
were they parallel also to the great branch ab.

8 Some of the stems of the six branches proceeded straight, and of a
thickness that gradually grew sharper towards the end, as ag.

9 Others of the stems of those branches grew bigger and knotty towards the
middle, and the branches also as well as stems, from Cylinders grew into
Plates, in a most admirable and curious order, so exceeding regular and
delicate, as nothing could be more, as is visible in ab, ac, ad, ae, af,
but towards the end of some of these stems, they began again to grow
smaller and to recover their former branchings, as about k and n.

10 Many of the _lateral_ branches had _collateral_ branches (if I may so
call them) as qm had many such as st, and most of those again
_subcollateral_, as vw, and these again had others less, which one may call
_laterosubcollateral_, and these again others, and they others, &c. in
greater Figures.

11 The branchings of the main Stems joyn'd not together by any regular
line, nor did one side of the one lie over the other side of the other, but
the small _collateral_ and _subcollateral_ branches did lie at top of one
another according to a certain order or method, which I always observ'd to
be this.

12 That side of a _collateral_ or _subcollateral_, &c. branch, lay over the
side of the _approximate_ (as the feathers in the wing of a Bird) whose
branchings proceeded parallel to the last biggest stem from which it
sprung, and not to the biggest stem of all, unless that were a second stem
backwards.

13 This rule that held in the branchings of the _Sexangular Figure_ held
also in the branchings of any other great or small stem, though it did not
proceed from a center.

14 The exactness and curiosity of the figuration of these branches, was in
every particular so transcendent, that I judge it almost impossible for
humane art to imitate.

15 Tasting several cleer pieces of this _Ice_, I could not find any
_Urinous_ taste in them, but those few I tasted, seem'd as _insipid_ as
water.

16 A figuration somewhat like this, though indeed in some particulars much
more curious, I have several times observ'd in _regulus martis stellatus_,
but with this difference, that all the stems and branchings are bended in a
most excellent and regular order, whereas in _Ice_ the stems and branchings
are streight, but in all other particulars it agrees with this, and seems
indeed nothing but one of these stars, or branched Figures frozen on
_Urine_, distorted, or wreathed a little, with a certain proportion: _Lead_
also that has _Arsenick_ and some other things mixt with it, I have found
to have its surface, when suffer'd to cool, figured somewhat like the
branchings of _Urine_, but much smaller.

17 But there is a _Vegetable_ which does exceedingly imitate these
branches, and that is, _Fearn_, where the main stem may be observ'd to
shoot out branches, and the stems of each of these _lateral_ branches, to
send forth _collateral_, and those _subcollateral_ and those
_laterosubcollateral,_ &c. and all those much after the same order with the
branchings, divisions, and subdivisions in the branchings of these Figures
in frozen _Urine_; so that if the Figures of both be well consider'd, one
would ghess that there were not much greater need of a _seminal principle_
for the production of _Fearn_, then for the production of the branches of
_Urine_, or the _Stella martis_, there seeming to be as much form and
beauty in the one as in the other.

And indeed, this Plant of _Fearn_, if all particulars be well consider'd,
will seem of as simple, and uncompounded a form as any _Vegetable_, next to
_Mould_ or _Mushromes_, and would next after the invention of the forms of
those, deserve to be enquir'd into; for notwithstanding several have
affirm'd it to have seed, and to be propagated thereby; yet, though I have
made very diligent enquiry after that particular, I cannot find that there
is any part of it that can be imagin'd to be more seminal then another: But
this onely here by the by:

For the freezing Figures in _Urine_, I found it requisite,

First, that the Superficies be not disturbed with any wind, or other
commotion of the air, or the like.

Secondly, that it be not too long exposed, so as that the whole bulk be
frozen, for oftentimes, in such cases, by reason of the swelling the of
_Ice_, or from some other cause, the curious branched Figures disappear.

Thirdly, an artificial freezing with _Snow_ and _Salt_, apply'd to the
outside of the containing Vessel, succeeds not well, unless there be a very
little quantity in the Vessel.

Fourthly, If you take any cleer and smooth Glass, and wetting all the
inside of it with _Urine_, you expose it to a very sharp freezing, you will
find it cover'd with a very regular and curious Figure.

II.

_Observables in figur'd _Snow_._

Exposing a piece of black Cloth, or a black Hatt to the falling _Snow_, I
have often with great pleasure, observ'd such an infinite variety of
curiously figur'd _Snow_, that it would be as impossible to draw the Figure
and shape of every one of them, as to imitate exactly the curious and
Geometrical _Mechanisme_ of Nature in any one. Some coorse draughts, such
as the coldness of the weather, and the ill provisions, I had by me for
such a purpose, would permit me to make, I have here added in the Second
_Figure_ of the Eighth _Scheme_.[12]

In all which I observ'd, that if they were of any regular Figures, they
were always branched out with six principal branches, all of equal length,
shape and make, from the center, being each of them inclin'd to either of
the next branches on either side of it, by an angle of sixty degrees.

Now, as all these stems were for the most part in one flake exactly of the
same make, so were they in differing Figures of very differing ones; so
that in a very little time I have observ'd above an hundred several cizes
and shapes of these starry flakes.

The branches also out of each stem of any one of these flakes, were exactly
alike in the same flake; so that of whatever Figure one of the branches
were, the other five were sure to be of the same, very exactly, that is, if
the branchings of the one were small _Perallelipipeds_ or Plates, the
branchings of the other five were of the same; and generally, the
branchings were very conformable to the rules and method observ'd before,
in the Figures on _Urine_, that is, the branchings from each side of the
stems were parallel to the next stem on that side, and if the stems were
plated, the branches also were the same; if the stems were very long, the
branches also were so, &c.

Observing some of these figur'd flakes with a _Microscope_, I found them
not to appear so curious and exactly figur'd as one would have imagin'd,
but like Artificial Figures, the bigger they were magnify'd, the more
irregularites appear'd in them; but this irregularity seem'd ascribable to
the thawing and breaking of the flake by the fall, and not at all to the
defect of the _plastick_ virtue of Nature, whose curiosity in the formation
of most of these kind of regular Figures, such as those of _Salt_,
_Minerals_, &c. appears by the help of the _Microscope_, to be very many
degrees smaller then the most acute eye is able to perceive without it. And
though one of these six-branched Stars appear'd here below much of the
shape described in the Third _Figure_ of the Eighth _Scheme_; yet I am very
apt to think, that could we have a sight of one of them through a
_Microscope_ as they are generated in the Clouds before their Figures are
vitiated by external accidents, they would exhibit abundance of curiosity
and neatness there also, though never so much magnify'd: For since I have
observ'd the Figures of _Salts_ and _Minerals_ to be some of them so
exceeding small, that I have scarcely been able to perceive them with the
_Microscope_, and yet have they been regular, and since (as far as I have
yet examin'd it) there seems to be but one and the same cause that produces
both these effects, I think it not irrational to suppose that these pretty
figur'd Stars of _Snow_, when at first generated might be also very regular
and exact.

III.

_Several kinds of Figures in _Water_ frozen._

Putting fair Water into a large capacious Vessel of _Glass_, and exposing
it to the cold, I observ'd after a little time, several broad, flat, and
thin _laminae_, or plates of _Ice_, crossing the bulk of the water and one
another very irregularly, onely most of them seem'd to turn one of their
edges towards that side of the Glass which was next it, and seem'd to grow,
as 'twere from the inside of the Vessel inwards towards the middle, almost
like so many blades of _Fern_. Having taken several of these plates out of
water on the blade of a Knife, I observ'd them figur'd much after the
manner of _Herring bones_, or _Fern blades_, that is, there was one bigger
stem in the middle like the back-bone, and out of it, on either side, were
a multitude of small _stiriae_, or _icicles_, like the smaller bones, or
the smaller branches in _Fern_, each of these branches on the one side,
were parallel to all the rest on the same side, and all of them seem'd to
make an angle with the stem, towards the top, of sixty degrees, and towards
the bottom or root of this stem, of 120. See the fourth _Figure_ of the 8.
_Plate_.

I observ'd likewise several very pretty Varieties of Figures in Water,
frozen on the top of a broad flat Marble-stone, expos'd to the cold with a
little Water on it, some like feathers, some of other shapes, many of them
were very much of the shape exprest in the fifth Figure of the 8. _Scheme_,
which is extremely differing from any of the other Figures.

I observ'd likewise, that the shootings of _Ice_ on the top of Water,
beginning to freez, were in streight _prismatical_ bodies much like those
of _roch-peter_, that they crost each other usually without any kind of
order or rule, that they were always a little higher then the surface of
the Water that lay between them; that by degrees those _interjacent_ spaces
would be fill'd with _Ice_ also, which usually would be as high as the
surface of the rest.

In flakes of _Ice_ that had been frozen on the top of Water to any
considerable thickness, I observ'd that both the upper and the under sides
of it were curiously quill'd, furrow'd, or grain'd, as it were, which when
the Sun shone on the Plate, was exceeding easily to be perceiv'd to be much
after the shape of the lines in the 6. _Figure_ of the 8. _Scheme_, that
is, they consisted of several streight ends of parallel Plates, which were
of divers lengths and angles to one another without any certain order.

The cause of all which regular Figures (and of hundreds of others, namely
of _Salts_, _Minerals_, _Metals,_ &c. which I could have here inserted,
would it not have been too long) seems to be deducible from the same
Principles, which I have (in the 13. _Observation_) hinted only, having not
yet had time to compleat a _Theory_ of them. But indeed (which I there also
hinted) I judge it the second step by which the _Pyramid_ of natural
knowledge (which is the knowledge of the form of bodies) is to be ascended:
And whosoever will climb it, must be well furnish'd with that which the
Noble _Verulam_ calls _Scalam Intellectus_; he must have scaling Ladders,
otherwise the steps are so large and high, there will be no getting up
them, and consequently little hopes of attaining any higher station, such
as to the knowledge of the most simple principle of Vegetation manifested
in Mould and Mushromes, which, as I elsewhere endeavoured to shew, seems to
be the third step; for it seems to me, that the Intellect of man is like
his body, destitute of wings, and cannot move from a lower to a higher and
more sublime station of knowledg, otherwise then step by step, nay even
there where the way is prepar'd and already made passible; as in the
_Elements of Geometry_, or the like, where it is fain to climb a whole
_series_ of Propositions by degrees, before it attains the knowledge of one
_Probleme_. But if the ascent be high, difficult and above its reach, it
must have recourse to a _novum organum_, some new engine and contrivance,
some new kind of _Algebra_, or _Analytick Art_ before it can surmount it.

* * * * *

Observ. XV. _Of _Kettering-stone_, and of the pores of _Inanimate_ bodies._

[13]This Stone which is brought from _Kettering_ in _Northampton-Shire_,
and digg'd out of a Quarry, as I am inform'd, has a grain altogether
admirable, nor have I ever seen or heard of any other stone that has the
like. It is made up of an innumerable company of small bodies, not all of
the same cize or shape, but for the most part, not much differing from a
Globular form, nor exceed they one another in Diameter above three or four
times; they appear to the eye, like the Cobb or Ovary of a _Herring_, or
some smaller fishes, but for the most part, the particles seem somewhat
less, and not so uniform; but their variation from a perfect globular ball,
seems to be only by the pressure of the _contiguous_ bals which have a
little deprest and protruded those toucht sides inward, and forc'd the
other sides as much outwards beyond the limits of a Globe; just as it would
happen, if a heap of exactly round Balls of soft Clay were heaped upon one
another; or, as I have often seen a heap of small Globules of
_Quicksilver_, reduc'd to that form by rubbing it much in a glaz'd Vessel,
with some slimy or sluggish liquor, such as Spittle, when though the top of
the upper Globules be very neer spherical, yet those that are prest upon by
others, exactly imitate the forms of these lately mention'd grains.

Where these grains touch each other, they are so firmly united or settled
together, that they seldom part without breaking a hole in one or th'other
of them, such as a, a, a, b, c, c, &c. Some of which fractions, as a, a, a,
a, where the touch has been but light, break no more then the outward
crust, or first shell of the stone, which is of a white colour, a little
dash'd with a brownish Yellow, and is very thin, like the shell of an Egg:
and I have seen some of those grains perfectly resemble some kind of Eggs,
both in colour and shape: But where the union of the _contiguous granules_
has been more firm, there the divulsion has made a greater Chasm, as at b,
b, b, in so much that I have observ'd some of them quite broken in two, as
at c, c, c, which has discovered to me a further resemblance they have to
Eggs, they having an appearance of a white and yelk, by two differing
substances that envelope and encompass each other.

That which we may call the white was pretty whitish neer the yelk, but more
duskie towards the shell; some of them I could plainly perceive to be shot
or radiated like a _Pyrites_ or _fire-stone_; the yelk in some I saw
hollow, in others fill'd with a duskie brown and porous substance like a
kind of pith.

The small pores, or _interstitia_ eeee betwixt the Globules, I plainly saw,
and found by other trials to be every way pervious to air and water, for I
could blow through a piece of this stone of a considerable thickness, as
easily as I have blown through a Cane, which minded me of the pores which
_Des Cartes_ allow his _materia subtilis_ between the _aethereal_ globules.

The object, through the _Microscope_, appears like a _Congeries_ or heap of
Pibbles, such as I have often seen cast up on the shore, by the working of
the Sea after a great storm, or like (in shape, though not colour) a
company of small Globules of Quicksilver, look'd on with a _Microscope_,
when reduc'd into that form by the way lately mentioned. And perhaps, this
last may give some hint at the manner of the formation of the former: For
supposing some _Lapidescent_ substance to be generated, or some way brought
(either by some commixture of bodies in the Sea it self, or protruded in,
perhaps, out of some _subterraneous_ caverns) to the bottom of the Sea, and
there remaining in the form of a liquor like Quicksilver, _heterogeneous_
to the ambient _Saline_ fluid, it may by the working and tumblings of the
Sea to and fro be jumbled and comminuted into such Globules as may
afterwards be hardned into Flints, the lying of which one upon another,
when in the Sea, being not very hard, by reason of the weight of the
incompassing fluid, may cause the undermost to be a little, though not
much, varied from a globular Figure. But this only by the by.

After what manner this _Kettering-stone_ should be generated I cannot
learn, having never been there to view the place, and observe the
circumstances; but it seems to me from the structure of it to be generated
from some substance once more fluid, and afterwards by degrees growing
harder, almost after the same manner as I supposed the generation of Flints
to be made.

But whatever were the cause of its curious texture, we may learn this
information from it; that even in those things which we account vile, rude,
and coorse, Nature has not been wanting to shew abundance of curiosity and
excellent Mechanisme.

We may here find a Stone by help of a _Microscope_, to be made up of
abundance of small Balls, which do but just touch each other, and yet there
being so many contacts, they make a firm hard mass, or a Stone much harder
then Free-stone.

Next, though we can by a _Microscope_ discern so curious a shape in the
particles, yet to the naked eye there scarce appears any such thing; which
may afford us a good argument to think, that even in those bodies also,
whose _texture_ we are not able to discern, though help'd with
_Microscopes_, there may be yet _latent_ so curious a _Schematisme_, that
it may abundantly satisfie the curious searcher, who shall be so happy as
to find some way to discover it.

Next, we here find a Stone, though to the naked eye a very close one, yet
every way perforated with innumerable pores, which are nothing else but the
_interstitia_, between those multitudes of minute globular particles, that
compose the bulk it self, and these pores are not only discover'd by the
_Microscope_, but by this contrivance.

I took a pretty large piece of this stone, and covering it all over with
cement, save only at two opposite parts, I found my self able, by blowing
in at one end that was left open, to blow my spittle, with which I had wet
the other end, into abundance of bubbles, which argued these pores to be
open and pervious through the whole stone, which affords us a very pretty
instance of the porousness of some seemingly close bodies, of which kind I
shall anon have occasion to subjoyn many more, tending to prove the same
thing.

I must not here omit to take notice, that in this body there is not a
_vegetative_ faculty that should so contrive this structure for any
peculiar use of _vegetation_ or growth, whereas in the other instances of
vegetable porous bodies, there is an _anima_ or _forma informans_, that
does contrive all the Structures and _Mechanismes_ of the constituting
body, to make them subservient and usefull to the great Work or Function
they are to perform. And so I ghess the pores in Wood, and other
vegetables, in bones, and other Animal substances, to be as so many
channels, provided by the Great and Alwise Creator, for the conveyance of
appropriated juyces to particular parts. And therefore, that this may tend,
or be pervious all towards one part, and may have impediments, as valves or
the like, to any other; but in this body we have very little reason so
suspect there should be any such design, for it is equally pervious every
way, not onely forward, but backwards, and side-ways, and seems indeed much
rather to be _Homogeneous_ or similar to those pores, which we may with
great probability believe to be the channels of _pellucid_ bodies, not
directed, or more open any one way, then any other, being equally pervious
every way. And, according as these pores are more or greater in respect of
the _interstitial_ bodies, the more transparent are the so constituted
concretes; and the smaller those pores are, the weaker is the _Impulse_ of
light communicated through them, though the more quick be the progress.

Upon this Occasion, I hope it will not be altogether unseasonable, if I
propound my conjectures and _Hypothesis_ about the _medium_ and conveyance
of light.

I suppose then, that the greatest part of the _Interstitia_ of the world,
that lies between the bodies of the Sun and Starrs, and the Planets, and
the Earth, to be an exceeding fluid body, very apt and ready to be mov'd,
and to communicate the motion of any one part to any other part, though
never so far distant: Nor do I much concern my self, to determine what the
Figure of the particles of this exceedingly subtile fluid _medium_ must be,
nor whether it have any interstitiated pores or vacuities, it being
sufficient to solve all the _Phaenomena_ to suppose it an exceedingly
fluid, or the most fluid body in the world, and as yet impossible to
determine the other difficulties.

That being so exceeding fluid a body, it easily gives passage to all other
bodies to move to and fro in it.

That it neither receives from any of its parts, or from other bodies; nor
communicates to any of its parts, or to any other body, any impulse, or
motion in a direct line, that is not of a determinate quickness. And that
when the motion is of such determinate swiftness, it both receives, and
communicates, or propagates an impulse or motion to any imaginable distance
in streight lines, with an unimaginable celerity and vigour.

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