Micrographia Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon 2 – Hooke · Verses Across
Literature · Science
Micrographia Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon 2Preface (part 2)
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Literature · Science
Micrographia Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon 2
Preface (part 2)
HookeEnglish
Now though this were the Instrument I made most use of, yet I have made several other Tryals with other kinds of Microscopes, which both for matter and form were very different from common spherical Glasses. I have made a Microscope with one piece of Glass, both whose surfaces were plains. I have made another only with a plano concave, without any kind of reflection, divers also by means of reflection. I have made others of Waters, Gums, Resins, Salts, Arsenick, Oyls, and with divers other mixtures of watery and oyly Liquors. And indeed the subject is capable of a great variety; but I find generally none more useful then that which is made with two Glasses, such as I have already describ’d.
What the things are I observ’d, the following descriptions will manifest; in brief, they were either exceeding small Bodies, or _exceeding small Pores, or exceeding small Motions_, some of each of which the Reader will find in the following Notes, and such, as I presume, (many of them at least) will be new, and perhaps not less strange: Some specimen of each of which Heads the Reader will find in the subsequent delineations, and indeed of some more then I was willing there should be; which was occasioned by my first Intentions to print a much greater number then I have since found time to compleat. Of such therefore as I had, I selected only some few of every Head, which for some particulars seem’d most observable, rejecting the rest as superfluous to the present Design.
What each of the delineated Subjects are, the following descriptions annext to each will inform, of which I shall here, only once for all, add, That in divers of them the Gravers have pretty well follow’d my directions and draughts; and that in making of them, I indeavoured (as far as I was able) first to discover the true appearance, and next to make a plain representation of it. This I mention the rather, because of these kind of Objects there is much more difficulty to discover the true shape, then of those visible to the naked eye, the same Object seeming quite differing, in one position to the Light, from what it really is, and may be discover’d in another. And therefore I never began to make any draught before by many examinations in several lights, and in several positions to those lights, I had discover’d the true form. For it is exceeding difficult in some Objects, to distinguish between a prominency and a depression, between a shadow and a black stain, or a reflection and a _whiteness in the colour_. Besides, the transparency of most Objects renders them yet much more difficult then if they were opacous. The Eyes of a Fly in one kind of light appear almost like a Lattice, drill’d through with abundance of small holes; which probably may be the Reason, why the Ingenious _Dr. Power_ seems to suppose them such. In the Sunshine they look like a Surface cover’d with golden Nails; in another posture, like a Surface cover’d with Pyramids; in another with Cones; and in other postures of quite other shapes; but that which exhibits the best, is the Light collected on the Object, by those means I have already describ’d.
And this was undertaken in prosecution of the Design which the _ROYAL SOCIETY_ has propos’d to it self. For the Members of the Assembly having before their eys so many fatal Instances of the errors and falshoods, in which the greatest part of mankind has so long wandred, because they rely’d upon the strength of humane Reason alone, have begun anew to correct all Hypotheses by sense, as Seamen do their dead Reckonings by _Cœlestial Observations_; and to this purpose it has been their principal indeavour to enlarge & strengthen the Senses by Medicine, and by such _outward Instruments_ as are proper for their particular works. By this means they find some reason to suspect, that those effects of Bodies, which have been commonly attributed to Qualities, and those confess’d to be occult, are perform’d by the small Machines of Nature, which are not to be discern’d without these helps, seeming the meer products of Motion, Figure, and Magnitude; and that the Natural Textures, which some call the _Plastick faculty, may be made in Looms_, which a greater perfection of Opticks may make discernable by these Glasses; so as now they are no more puzzled about them, then the vulgar are to conceive, how Tapestry or flowred Stuffs are woven. And the ends of all these Inquiries they intend to be the Pleasure of Contemplative minds, but above all, the ease and dispatch of the labours of mens hands. They do indeed neglect no opportunity to bring all the rare things of Remote Countries within the compass of their knowledge and practice. But they still acknowledg their most useful Informations to arise from common things, and from diversifying their most ordinary operations upon them. They do not wholly reject Experiments of meer light and theory; but they principally aim at such, whose Applications will improve and facilitate the present way of _Manual Arts_. And though some men, who are perhaps taken up about less honourable Employments, are pleas’d to censure their proceedings, yet they can shew more fruits of their first three years, wherein they have assembled, then any other Society in Europe can for a much larger space of time. ’Tis true, such undertakings as theirs do commonly meet with small incouragement, because men are generally rather taken with the plausible and discursive, then the real and the solid part of Philosophy; yet by the good fortune of their institution, in an Age of all others the most inquisitive, they have been assisted by the contribution and presence of very many of the chief Nobility and Gentry, and others who are some of the most considerable in their several Professions. But that that yet farther convinces me of the Real esteem that the more serious part of men have of this Society, is, that several Merchants, men who act in earnest (whose Object is meum & tuum, that great Rudder of humane affairs) have adventur’d considerable sums of Money, to put in practice what some of our Members have contrived, and have continued stedfast in their good opinions of such Indeavours, when not one of a hundred of the vulgar have believed their undertakings feasable. And it is also fit to be added, that they have one advantage peculiar to themselves, that very many of their number are men of Converse and Traffick; which is a good Omen, that their attempts will bring Philosophy from words to action, seeing the men of Business have had so great a share in their first foundation.
And of this kind I ought not to conceal one particular Generosity, which more nearly concerns my self. It is the munificence of Sir John Cutler, in endowing a Lecture for the promotion of Mechanick Arts, to be governed and directed by This Society.This Bounty I mention for the Honourableness of the thing it self, and for the expectation which I have of the efficacy of the Example; for it cannot now be objected to them, that their Designs will be esteemed frivolous and vain, when they have such a real Testimony of the Approbation of a Man that is such an eminent Ornament of this renowned City, and one, who, by the Variety, and the happy Success, of his negotiations, has given evident proofs, that he is not easie to be deceiv’d. This Gentleman has well observ’d, that the Arts of life have been too long imprison’d in the dark shops of Mechanicks themselves, & there hindred from growth, either by ignorance, or self-interest: and he has bravely freed them from these inconveniences: He hath not only obliged Tradesmen, but Trade it self: He has done a work that is worthy of London, and has taught the chief City of Commerce in the world the right way how Commerce is to be improv’d. We have already seen many other great signs of Liberality and a large mind, from the same hand: For by his diligence about the Corporation for the Poor; by his honorable Subscriptions for the rebuilding of St. Paul’s; by his chearful Disbursment for the replanting of Ireland, and by many other such publick works, he has shewn by what means he indeavours to establish his Memory; and now by this last gift he has done that, which became one of the wisest Citizens of our Nation to accomplish, seeing one of the wisest of our Statesmen, the Lord Verulam, first propounded it.
But to return to my Subject, from a digression, which, I hope, my Reader will pardon me, seeing the Example is so rare that I can make no more such digressions. If these my first Labours shall be any wayes useful to inquiring men, I must attribute the incouragement and promotion of them to a very Reverend and Learned Person, of whom this ought in justice to be said, _That there is scarce any one Invention, which this Nation has produc’d in our Age, but it has some way or other been set forward by his assistance. My Reader, I believe, will quickly ghess, that it is Dr. Wilkins_ that I mean. He is indeed a man born for the good of mankind, and for the honour of his Country. In the sweetness of whose behaviour, in the calmness of his mind, in the unbounded goodness of his heart, we have an evident Instance, what the true and the primitive unpassionate Religion was, before it was sowred by particular Factions. In a word, his Zeal has been so constant and effectual in advancing all good and profitable Arts, that as one of the Antient Romans said of Scipio, That he thanked God that he was a Roman_; because whereever Scipio had been born, there had been the seat of the Empire of the world: So may I thank God, that Dr. Wilkins_ was an Englishman, for whereever he had lived, there had been the chief Seat of generous Knowledge and true Philosophy. To the truth of this, there are so many worthy men living that will subscribe, that I am confident, what I have here said, will not be looked upon, by any ingenious Reader, as a Panegyrick, but only as a real testimony.
By the Advice of this Excellent man I first set upon this Enterprise, yet still came to it with much Reluctancy, because I was to follow the footsteps of so eminent a Person as Dr. Wren, who was the first that attempted any thing of this nature; whose original draughts do now make one of the Ornaments of that great Collection of Rarities in the _Kings Closet. This Honor_, which his first beginnings of this kind have receiv’d, to be admitted into the most famous place of the world, did not so much incourage, as the hazard of coming after Dr. Wren did affright me; for of him I must affirm, that, since the time of Archimedes, there scarce ever met in one man, in so great a perfection, such a Mechanical Hand, and so Philosophical a Mind.
But at last, being assured both by Dr. Wilkins, and Dr. Wren himself, that he had given over his intentions of prosecuting it, and not finding that there was any else design’d the pursuing of it, I set upon this undertaking, and was not a little incourag’d to proceed in it, by the Honour the Royal Society was pleas’d to favour me with, in approving of those draughts (which from time to time as I had an opportunity of describing) I presented to them. And particularly by the Incitements of divers of those Noble and excellent Persons of it, which were my more especial Friends, who were not less urgent with me for the publishing, then for the prosecution of them.
After I had almost compleated these Pictures and Observations (having had divers of them engraven, and was ready to send them to the Press) I was inform’d, that the Ingenious Physitian Dr. Henry Power had made several Microscopical Observations, which had I not afterwards, upon our interchangably viewing each others Papers, found that they were for the most part differing from mine, either in the Subject it self, or in the particulars taken notice of; and that his design was only to print Observations without Pictures, I had even then suppressed what I had so far proceeded in. But being further excited by several of my Friends, in compliance with their opinions, that it would not be unacceptable to several inquisitive Men, and hoping also, that I should thereby discover something New to the World, I have at length cast in my Mite, into the vast Treasury of A Philosophical History. And it is my hope, as well as belief, that these my Labours will be no more comparable to the Productions of many other Natural Philosophers, who are now every where busie about greater things; then my little Objects are to be compar’d to the greater and more beautiful Works of Nature, A Flea, a Mite, a Gnat, to an Horse, an Elephant, or a Lyon.
MICROGRAPHIA,
OR SOME
Physiological Descriptions
OF
MINUTE BODIES,
MADE BY
MAGNIFYING GLASSES;
WITH
OBSERVATIONS and INQUIRIES thereupon.
Observ. I. Of the Point of a sharp small Needle.
As in Geometry, the most natural way of beginning is from a Mathematical point; so is the same method in Observations and Natural history the most genuine, simple, and instructive. We must first endevour to make letters, and draw single strokes true, before we venture to write whole Sentences, or to draw large Pictures. And in Physical Enquiries, we must endevour to follow Nature in the more plain and easie ways she treads in the most simple and uncompounded bodies, to trace her steps, and be acquainted with her manner of walking there, before we venture our selves into the multitude of meanders she has in _bodies of a more complicated_ nature; lest, being unable to distinguish and judge of our way, we quickly lose both Nature our Guide, and our selves too, and are left to wander in the labyrinth of groundless opinions; wanting both judgment, that light, and experience, that clew, which should direct our proceedings.
We will begin these our Inquiries therefore with the Observations of Bodies of the most simple nature first, and so gradually proceed to those of a more compounded one. In prosecution of which method, we shall begin with a Physical point; of which kind the Point of a Needle is commonly reckon’d for one; and is indeed, for the most part, made so sharp, that the naked eye cannot distinguish any parts of it: It very easily pierces, and makes its way through all kind of bodies softer then it self: But if view’d with a very good Microscope, we may find that the top of a Needle (though as to the sense very sharp) appears a broad, blunt, and very irregular end; not resembling a Cone, as is imagin’d, but onely a piece of a tapering body, with a great part of the top remov’d, or deficient. The Points of Pins are yet more blunt, and the Points of the most curious Mathematical Instruments do very seldome arrive at so great a sharpness; how much therefore can be built upon demonstrations made onely by the productions of the Ruler and Compasses, he will be better able to consider that shall but view those points and lines with a Microscope.
Now though this point be commonly accounted the sharpest (whence when we would express the sharpness of a point the most superlatively, we say, As sharp as a Needle) yet the Microscope can afford us hundreds of Instances of Points many thousand times sharper: such as those of the hairs, and bristles, and claws of multitudes of Insects; the thorns, or crooks, or hairs of leaves, and other small vegetables; nay, the ends of the stiriæ or small parallelipipeds of Amianthus, and _alumen plumosum_; of many of which, though the Points are so sharp as not to be visible, though view’d with a Microscope (which magnifies the Object, in bulk, above a million of times) yet I doubt not, but were we able practically to make Microscopes according to the theory of them, we might find hills, and dales, and pores, and a sufficient bredth, or expansion, to give all those parts elbow-room, even in the blunt top of the very Point of any of these so very sharp bodies. For certainly the quantity or extension of any body may be Divisible in infinitum, though perhaps not the matter.
But to proceed: The Image we have here exhibited in the first Figure, was the top of a small and very sharp Needle, whose point aa nevertheless appear’d through the Microscope above a quarter of an inch broad, not round nor flat, but irregular and uneven; so that it seem’d to have been big enough to have afforded a hundred armed Mites room enough to be rang’d by each other without endangering the breaking one anothers necks, by being thrust off on either side. The surface of which, though appearing to the naked eye very smooth, could not nevertheless hide a multitude of holes and scratches and ruggednesses from being discover’d by the Microscope to invest it, several of which inequalities (as A, B, C, seem’d holes made by some small specks of Rust; and D some adventitious body, that stuck very close to it) were casual. All the rest that roughen the surface, were onely so many marks of the rudeness and bungling of Art. So unaccurate is it, in all its productions, even in those which seem most neat, that if examin’d with an organ more acute then that by which they were made, the more we see of their shape, the less appearance will there be of their beauty: whereas in the works of Nature, the deepest Discoveries shew us the greatest Excellencies. An evident Argument, that he that was the Author of all these things, was no other then Omnipotent; being able to include as great a variety of parts and contrivances in the yet smallest Discernable Point, as in those vaster bodies (which comparatively are called also Points) such as the Earth, Sun, or Planets. Nor need it seem strange that the Earth it self may be by an Analogie call’d a Physical Point: For as its body, though now so near us as to fill our eys and fancies with a sense of the vastness of it, may by a little Distance, and some convenient Diminishing Glasses, be made vanish into a scarce visible Speck, or Point (as I have often try’d on the Moon, and (when not too bright) on the Sun it self.) So, could a Mechanical contrivance succesfully answer our Theory, we might see the least spot as big as the Earth it self; and Discover, as Des Cartes also conjectures, as great a variety of bodies in the Moon, or Planets, as in the Earth.
But leaving these Discoveries to future Industries, we shall proceed to add one Observation more of a point commonly so call’d, that is, the mark of a full stop, or period. And for this purpose I observed many both printed ones and written; and among multitudes I found few of them more round or regular then this which I have delineated in the third figure of the second Scheme, but very many abundantly more disfigur’d; and for the most part if they seem’d equally round to the eye, I found those points that had been made by a Copper-plate, and Roll-press, to be as misshapen as those which had been made with Types, the most curious and smothly engraven strokes and points, looking but as so many furrows and holes, and their printed impressions, but like _smutty daubings_ on a matt or uneven floor with a blunt extinguisht brand or stick’s end. And as for points made with a pen they were much _more ragged_ and deformed. Nay, having view’d certain pieces of exceeding curious writing of the kind (one of which in the bredth of a two-pence compris’d _the Lords prayer, the Apostles Creed, the ten Commandments, and about half a dozen verses besides of the Bible, whose lines_ were _so small_ and near together, that I was unable to number them with my naked eye,) a very ordinary Microscope, I had then about me, inabled me to see that what the Writer of it had asserted was true, but withall discover’d of what pitifull bungling scribbles and scrawls it was compos’d, Arabian and China characters being almost as well shap’d, yet thus much I must say for the Man, that it was for the most part legible enough, though in some places there wanted a good fantsy well preposest to help one through. If this manner of small writing were made easie and practicable (and I think I know such a one, but have never yet made tryal of it, whereby one might be inabled to write a great deale with much ease, and accurately enough in a very little roome) it might be of very good use to convey secret Intelligence without any danger of Discovery or mistrusting. But to come again to the point. The Irregularities of it are caused by three or four coadjutors, one of which is, the uneven surface of the paper, which at best appears no smother then a very course piece of shag’d cloth, next the _irregularity of the Type_ or Ingraving, and a third is the rough Daubing of the Printing-Ink that lies upon the instrument that makes the impression, to all which, add the variation made by the Different lights and shadows, and you may have sufficient reason to ghess that a point may appear much more ugly then this, which I have here presented, which though it appear’d through the Microscope gray, like a great splatch of London dirt, about three inches over; yet to the naked eye it was black and no bigger then that in the midst of the Circle A. And could I have found Room in this Plate to have inserted an O you should have seen that the letters were not more distinct then the points of Distinction, nor a drawn circle more exactly so, then we have now shown a point to be a point.
Observ. II. Of the Edge of a Razor.
The sharpest Edge hath the same kind of affinity to the sharpest Point in Physicks, as a line hath to a point in Mathematicks; and therefore the Treaty concerning this, may very properly be annexed to the former. A Razor doth appear to be a Body of a very neat and curious aspect, till more closely viewed by the Microscope, and there we may observe its very Edge to be of all kind of shapes, except what it should be. For examining that of a very sharp one, I could not find that any part of it had any thing of sharpness in it; but it appeared a rough surface of a very considerable bredth from side to side, the narrowest part not seeming thinner then the back of a pretty thick Knife. Nor is’t likely that it should appear any otherwise, since as we just now shew’d that a point appear’d a circle, ’tis rational a line should be a parallelogram.
Now for the drawing this second Figure (which represents a part of the Edge about half a quarter of an inch long of a Razor well set) I so plac’d it between the Object-glass & the light, that there appear’d a reflection from the very Edge, represented by the white line abcdef. In which you may perceive it to be somewhat sharper then elsewhere about d, to be indented or pitted about b, to be broader and thicker about c, and unequal and rugged about e, and pretty even between ab and ef. Nor was that part of the Edge ghik so smooth as one would imagine so smooth bodies as a Hone and Oyl should leave it; for besides those multitudes of scratches, which appear to have raz’d the surface ghik, and to cross each other every way which are not half of them exprest in the Figure, there were several great and deep scratches, or furrows, such as gh and ik, which made the surface yet more rugged, caus’d perhaps by some small Dust casually falling on the Hone, or some harder or more flinty part of the Hone it self. The other part of the Razor ll, which is polish’d on a grinding-stone, appear’d much rougher then the other, looking almost like a plow’d field, with many parallels, ridges, and furrows, and a cloddy, as ’twere, or an uneven surface: nor shall we wonder at the roughnesses of those surfaces, since even in the most curious wrought Glasses for Microscopes, and other Optical uses, I have, when the Sun has shone well on them, discover’d their surface to be variously raz’d or scratched, and to consist of an infinite of small broken surfaces, which reflect the light of very various and differing colours. And indeed it seems impossible by Art to cut the surface of any hard and brittle body smooth, since Putte, or even the most curious Powder that can be made use of, to polish such a body, must consist of little hard rough particles, and each of them must cut its way, and consequently leave some kind of gutter or furrow behind it. And though Nature does seem to do it very readily in all kinds of fluid bodies, yet perhaps future observators may discover even these also rugged; it being very probable, as I elsewhere shew, that fluid bodies are made up of small solid particles variously and strongly mov’d, and may find reason to think there is scarce a surface _in rerum naturâ_ perfectly smooth. The black spot mn, I ghess to be some small speck of rust, for that I have oft observ’d to be the manner of the working of Corrosive Juyces. To conclude, this Edge and piece of a Razor, if it had been really such as it appear’d through the Microscope, would scarcely have serv’d to cleave wood, much less to have cut off the hair of beards, unless it were after the manner that Lucian merrily relates Charon to have made use of, when with a Carpenters Axe he chop’d off the beard of a sage Philosopher, whose gravity he very cautiously fear’d would indanger the oversetting of his Wherry.
Observ. III. Of fine Lawn, or Linnen Cloth.
This is another product of Art, A piece of the finest Lawn I was able to get, so curious that the threads were scarce discernable by the naked eye, and yet through an ordinary Microscope you may perceive what a goodly piece of coarse Matting it is; what proportionable cords each of its threads are, being not unlike, both in shape and size, the bigger and coarser kind of single Rope-yarn, wherewith they usually make Cables. That which makes the Lawn so transparent, is by the Microscope, nay by the naked eye, if attentively viewed, plainly enough evidenced to be the multitude of square holes which are left between the threads, appearing to have much more hole in respect of the intercurrent parts then is for the most part left in a lattice-window, which it does a little resemble, onely the crossing parts are round and not flat.
These threads that compose this fine contexture, though they are as small as those that constitute the finer sorts of Silks, have notwithstanding nothing of their glossie, pleasant, and lively reflection. Nay, I have been informed both by the Inventor himself, and several other eye-witnesses, that though the flax, out of which it is made, has been (by a singular art, of that excellent Person, and Noble Virtuoso, M. Charls Howard, brother to the Duke of Norfolk) so curiously dress’d and prepar’d, as to appear both to the eye and the touch, full as fine and as glossie, and to receive all kinds of colours, as well as Sleave-Silk; yet when this Silken Flax is twisted into threads, it quite loseth its former luster, and becomes as plain and base a thread to look on, as one of the same bigness, made of common Flax.
The reason of which odd Phenomenon seems no other then this; that though the curiously drest Flax has its parts so exceedingly small, as to equallize, if not to be much smaller then the clew of the Silk-worm, especially in thinness, yet the differences between the figures of the constituting filaments are so great, and their substances so various, that whereas those of the Silk are small, round, hard, transparent, and to their bigness proportionably stiff, so as each filament preserves its proper Figure, and consequently its vivid reflection intire, though twisted into a thread, if not too hard; those of Flax are flat, limber, softer, and less transparent, and in twisting into a thread they joyn, and lie so close together, as to lose their own, and destroy each others particular reflections. There seems therefore three Particulars very requisite to make the so drest Flax appear Silk also when spun into threads. First, that the substance of it should be made more clear and transparent, Flax retaining in it a kind of opacating brown, or yellow; and the parts of the whitest kind I have yet observ’d with the Microscope appearing white, like flaw’d Horn or Glass, rather then clear, like clear Horn or Glass. Next that, the filaments should each of them be rounded, if that could be done, which yet is not so very necessary, if the first be perform’d, and this third, which is, that each of the small filaments be stifned; for though they be square, or flat, provided they be transparent and stiff, much the same appearances must necessarily follow. Now, though I have not yet made trial, yet I doubt not, but that both these proprieties may be also induc’d upon the Flax, and perhaps too by one and the same Expedient, which some trials may quickly inform any ingenious attempter of, who from the use and profit of such an Invention, may find sufficient argument to be prompted to such Inquiries. As for the tenacity of the substance of Flax, out of which the thread is made, it seems much inferiour to that of Silk, the one being a vegetable, the other an animal substance. And whether it proceed from the better concoction, or the more homogeneous constitution of animal substances above those of vegetables, I do not here determine; yet since I generally find, that vegetable substances do not equalize the tenacity of animal, nor these the tenacity of some purified mineral substances; I am very apt to think, that the tenacity of bodies does not proceed from the hamous, or hooked particles, as the Epicureans and some modern Philosophers have imagin’d; but from the more exact congruity of the constituent parts, which are contiguous to each other, and so bulky, as not to be easily separated, or shatter’d, by any small pulls or concussion of heat.
Observ. IV. Of fine waled Silk, or Taffety.
This is the appearance of a piece of very fine Taffety-riband in the bigger magnifying Glass, which you see exhibits it like a very convenient substance to make Bed-matts, or Door-matts of, or to serve for Beehives, Corn-scuttles, Chairs, or Corn-tubs, it being not unlike that kind of work, wherewith in many parts in England, they make such Utensils of Straw, a little wreathed, and bound together with thongs of Brambles. For in this Contexture, each little filament, fiber, or clew of the Silk-worm, seem’d about the bigness of an ordinary Straw, as appears by the little irregular pieces, ab, cd, and ef; The Warp, or the thread that ran crossing the Riband, appear’d like a single Rope of an Inch Diameter; but the Woof, or the thread that ran the length of the Riband, appear’d not half so big. Each Inch of six-peny-broad Riband appearing no less then a piece of Matting Inch and half thick, and twelve foot square, a few yards of this, would be enough to floor the long Gallery of the Loure at Paris. But to return to our piece of Riband: It affords us a not unpleasant object, appearing like a bundle, or wreath, of very clear and transparent Cylinders, if the Silk be white, and curiously ting’d; if it be colour’d, each of those small horney Cylinders affording in some place or other of them, as vivid a reflection, as if it had been sent from a Cylinder of Glass or Horn. Insomuch, that the reflections of Red, appear’d as if coming from so many Granates, or Rubies. The loveliness of the colours of Silks above those of hairy Stuffs, or Linnen, consisting, as I else-where intimate, chiefly in the transparency, and vivid reflections from the Concave, or inner surface of the transparent Cylinder, as are also the colours of Precious Stones; for most of the reflections from each of these Cylinders, come from the Concave surface of the air, which is as ’twere the foil that incompasses the Cylinder. The colours with which each of these Cylinders are ting’d, seem partly to be superficial, and sticking to the out-sides of them; and partly, to be imbib’d, or sunck into the substance of them: for Silk, seeming to be little else then a dried thread of Glew, may be suppos’d to be very easily relaxt, and softened, by being steeped in warm, nay in cold, if penetrant, juyces or liquors. And thereby those tinctures, though they tinge perhaps but a small part of the substance, yet being so highly impregnated with the colour, as to be almost black with it, may leave an impression strong enough to exhibite the desir’d colour. A pretty kinde of artificial Stuff I have seen, looking almost like transparent Parchment, Horn, or Ising-glass, and perhaps some such thing it may be made of, which being transparent, and of a glutinous nature, and easily mollified by keeping in water, as I found upon trial, had imbib’d, and did remain ting’d with a great variety of very vivid colours, and to the naked eye, it look’d very like the substance of the Silk. And I have often thought, that probably there might be a way found out, to make an artificial glutinous composition, much resembling, if not full as good, nay better, then that Excrement, or whatever other substance it be out of which, the Silk-worm wire-draws his clew. If such a composition were found, it were certainly an easie matter to find very quick ways of drawing it out into small wires for use. I need not mention the use of such an Invention, nor the benefit that is likely to accrue to the finder, they being sufficiently obvious. This hint therefore, may, I hope, give some Ingenious inquisitive Person an occasion of making some trials, which if successfull, I have my aim, and I suppose he will have no occasion to be displeas’d.
Observ. V. Of watered Silks, or Stuffs.
There are but few Artificial things that are worth observing with a Microscope, and therefore I shall speak but briefly concerning them. For the Productions of art are such rude mis-shapen things, that when view’d with a Microscope, is little else observable, but their deformity. The most curious Carvings appearing no better then those rude Russian Images we find mention’d in Purchas, where three notches at the end of a Stick, stood for a face. And the most smooth and burnish’d surfaces appear most rough and unpolisht: So that my first Reason why I shall add but a few observations of them, is, their mis-shapen form; and the next, is their uselessness. For why should we trouble our selves in the examination of that form or shape (which is all we are able to reach with a Microscope) which we know was design’d for no higher a use, then what we were able to view with our naked eye? Why should we endeavour to discover mysteries in that which has no such thing in it? And like Rabbins find out Caballisms, and ænigmâs in the Figure, and placing of Letters, where no such thing lies hid: whereas in natural forms there are some so small, and so curious, and their design’d business so far remov’d beyond the reach of our sight, that the more we magnify the object, the more excellencies and mysteries do appear; And the more we discover the imperfections of our senses; and the Omnipotency and Infinite perfections of the great Creatour. I shall therefore onely add one or two Observations more artificial things, and then come to the Treaty concerning such matters as are the Productions of a more curious Workman. One of these, shall be that of a piece of water’d Silk, represented in the second Figure of the third Scheme, as it appear’d through the least magnifying Glass. AB signifying the long way of the Stuff, and CD the broad way. This Stuff, if the right side of it be looked upon, appears to the naked eye, all over so waved, undulated, or grain’d, with a curious, though irregular variety of brighter and darker parts, that it adds no small gracefulness to the Gloss of it.
It is so known a propriety, that it needs but little explication, but it is observable, which perhaps everyone has not considered, that those parts which appear the darker part of the wave, in one position to the light, in another appears the lighter, and the contrary; and by this means the undulations become transient, and in a continual change, according as the position of the parts in respect of the incident beams of light is varied. The reason of which odd phænomena, to one that has but diligently examin’d it even with his naked eye, will be obvious enough. But he that observes it with a Microscope, may more easily perceive what this Proteus is, and how it comes to change its shape. He may very easily perceive, that it proceeds onely from the variety of the Reflections of light, which is caus’d by the various _shape of the Particles_, or little protuberant parts of the thread that compose the surface; and that those parts of the waves that appear the brighter, throw towards the eye a multitude of small reflections of light, whereas the darker scarce afford any. The reason of which reflection, the Microscope plainly discovers, as appears by the Figure. In which you may perceive, that the brighter parts of the surface consist of an abundance of large and strong reflections, denoted by a, a, a, a, a, &c.
for the surfaces of those threads that run the long way, are by the Mechanical process of watering, creas’d or angled in another kind of posture then they were by the weaving: for by the weaving they are onely bent round the warping threads; but by the watering, they are bent with an angle, or elbow, that is in stead of lying, or being bent round the threads, as in the third Figure, a, a, a, a, a, are about b, b, b (b, b, b representing the ends, as ’twere, of the cross threads, they are bent about) they are creas’d on the top of those threads, with an angle, as in the fourth Figure, and that with all imaginable variety; so that, whereas before they reflected the light onely from one point of the round surface, as about c, c, c, they now when water’d, reflect the beams from more then half the whole surface, as de, de, de, and in other postures they return no reflections at all from those surfaces. Hence in one posture they compose the brighter parts of the waves, in another the darker. And these reflections are also varied, according as the particular parts are variously bent. The reason of which creasing we shall next examine; and here we must fetch our information from the Mechanism or manner of proceeding in this operation; which, as I have been inform’d, is no other then this.
They double all the Stuff that is to be water’d, that is, they crease it just through the middle of it, the whole length of the piece, leaving the right side of the Stuff inward, and placing the two edges, or silvages just upon one another, and, as near as they can, place the wale so in the doubling of it, that the wale of the one side may lie very near parallel, or even with the wale of the other; for the nearer that posture they lie, the greater will the watering appear; and the more obliquely, or across to each other they lie, the smaller are the waves. Their way for folding it for a great wale is thus: they take a Pin, and begin at one side of the piece in any wale, and so moving it towards the other side, thereby direct their hands to the opposite ends of the wale, and then, as near as they can, place the two opposite ends of the same wale together, and so double, or fold the whole piece, repeating this enquiry with a Pin at every yard or two’s distance through the whole length; then they sprinkle it with water, and fold it the long-ways, placing between every fold a piece of Pastboard, by which means all the wrong side of the water’d Stuff becomes flat, and with little wales, and the wales on the other side become the more protuberant; whence the creasings or angular bendings of the wales become the more perspicuous. Having folded it in this manner, they place it with an interjacent Pastboard into an hot Press, where it is kept very violently prest, till it be dry and stiff; by which means, the wales of either contiguous sides leave their own impressions upon each other, as is very manifest by the second Figure, where ’tis obvious enough, that the wale of the piece ABCD runs parallel between the pricked lines ef, ef, ef, and as manifest to discern the impressions upon these wales, left by those that were prest upon them, which lying not exactly parallel with them, but a little athwart them, as is denoted by the lines of, oooo, gh, gh, gh, between which the other wales did lie parallel; they are so variously, and irregularly creas’d that being put into that shape when wet, and kept so till they be drie, they so let each others threads, that the Moldings remain almost as long as the Stuff lasts.
Hence it may appear to any one that attentively considers the Figure, why the parts of the wale a, a, a, a, a, a, should appear bright; and why the parts b, b, b, b, b, b, b, should appear shadowed, or dark; why some, as d, d, d, d, d, d, should appear partly light, and partly dark: the varieties of which reflections and shadows are the only cause of the appearance of watering in Silks, or any other kind of Stuffs.
From the variety of reflection, may also be deduc’d the cause why a small breez or gale of wind ruffling the surface of a smooth water, makes it appear black; as also, on the other side, why the smoothing or burnishing the surface of whitened Silver makes it look black; and multitudes of other phænomena might hereby be solv’d, which are too many to be here insisted on.
Observ. VI. Of Small Glass Canes.
That I might be satisfi’d, whether it were not possible to make an Artificial pore as small as any Natural I had yet found, I made several attempts with small glass pipes, melted in the flame of a Lamp, and then very suddenly drawn out into a great length. And, by _that means_, without much difficulty, I was able to draw some almost as small as a Cobweb, which yet, with the Microscope, I could plainly perceive to be perforated, both by looking on the ends of it, and by looking on it against the light which was much the easier way to determine whether it were solid or perforated; for, taking a small pipe of glass, and closing one end of it, then filling it half full of water, and holding it against the light, I could, by this means, very easily find what was the differing aspect of a solid and a perforated piece of glass; and so easily distinguish, without seeing either end, whether any Cylinder of glass I look’d on, were a solid stick, or a hollow cane. And by this means, I could also presently judge of any small filament of glass, whether it were hollow or not, which would have been exceeding tedious to examine by looking on the end. And many such like ways I was fain to make use of, in the examining of divers other particulars related in this Book, which would have been no easie task to have determined meerly by the more common way of looking on, or viewing the Object. For, if we consider first, the very faint light wherewith the object is enlightened, whence many particles appear opacous, which when more enlightned, appear very transparent, so that I was fain to determine its transparency by one glass, and its texture by another. Next, the unmanageableness of most Objects, by reason of their smalness, 3. The difficulty of finding the desired point, and of placing it so, as to reflect the _light conveniently_ for the Inquiry. Lastly, ones being able to view it but with one eye at once, they will appear no small obstructions, nor are they easily remov’d without many contrivances. But to proceed, I could not find that water, or some deeply ting’d liquors would in small ones rise so high as one would expect; and the highest I have found it yet rise in any of the pipes I have try’d, was to 21 inches above the level of the water in the vessel: for though I found that in the small pipes it would nimbly enter at first, and run about 6 or 7 inches upwards; yet I found it then to move upwards so slow, that I have not yet had the patience to observe it above that height of 21 inches (and that was in a pretty large Pipe, in comparison of those I formerly mentioned; for I could observe the progress of a very deep ting’d liquor in it with my _naked eye, without much trouble; whereas many of the other pipes_ were so _very small, that unless in a convenient posture_ to the light, I could not perceive them:) But ’tis very probable, that a greater patience and assiduity may discover the liquors to rise, at least to remain suspended, at heights that I should be loath now even to ghess at, if at least there be any proportion kept between the height of the ascending liquor, and the bigness of the holes of the pipes.
AN ATTEMPT FOR THE EXPLICATION OF THIS EXPERIMENT.
My Conjecture, _That the unequal height of the surfaces of the water, proceeded from the greater pressure made upon the water by the Air without the Pipes_ ABC, then by that within them; I shall endeavour to confirm from the truth of the two following Propositions:
The first of which is, _That an unequal pressure of the incumbent Air, will cause an unequal height in the water’s Surfaces_.
And the second is, _That in this experiment there is such an unequal pressure_.
That the first is true, the following Experiment will evince. For if you take any Vessel so contrived, as that you can at pleasure either increase or diminish the pressure of the Air upon this or that part of the Superficies of the water, the equality of the height of those parts will presently be lost; and that part of the Superficies that sustains the greater pressure, will be inferior to that which undergoes the less. A fit Vessel for this purpose, will be an inverted Glass Syphon, such an one as is described in the Sixth Figure. For if into it you put Water enough to fill it as high as AB, and gently blow in at D, you shall depress the Superficies B, and thereby raise the opposite Superficies A to a considerable height, and by gently sucking you may produce clean contrary effects.
Next, That there is such an unequal pressure, I shall prove from this, _That there is a much greater incongruity of Air to Glass, and some other Bodies, then there is of Water to the same_.
By _Congruity, I mean a property of a fluid Body, whereby any part of it is readily united with any other part, either of itself, or of any other Similar, fluid, or solid body: And by Incongruity a property of a fluid, by which it is hindred from uniting with any dissimilar, fluid, or solid Body._
This last property, any one that hath been observingly conversant about fluid Bodies, cannot be ignorant of. For (not now to mention several Chymical Spirits and Oyls, which will very hardly, if at all, be brought to mix with one another; insomuch that there may be found some 8 or 9, or more, several distinct Liquors, which swimming one upon another, will not presently mix) we need seek no further for Examples of this kind in fluids, then to observe the drops of rain falling through the air and the bubbles of air which are by any means conveyed under the surface of the water; or a drop of common Sallet-Oyl swimming upon water. In all which, and many more examples of this kind that might be enumerated, the incongruity of two fluids is easily discernable. And as for the Congruity or Incongruity of Liquids, with several kinds of firm Bodies, they have long since been taken notice of, and called by the Names of Driness and Moisture (though these two names are not comprehensive enough, being commonly used to signifie only the adhering or not adhering of water to some other solid Bodies) of this kind we may observe that water will more readily wet some woods then others; and that water, let fall upon a Feather, the whiter side of a Colwort, and some other leaves, or upon almost any dusty, unctuous, or resinous superficies, will not at all adhere to them, but easily tumble off from them, like a solid Bowl; whereas, if dropt upon Linnen, Paper, Clay, _green Wood_, &c. it will not be taken off, without leaving some part of it behind adhering to them. So Quick-silver, which will very hardly be brought to stick to any vegetable body, will readily adhere to, and mingle with, several clean metalline bodies.
And that we may the better finde what the cause of Congruity and Incongruity in bodies is, it will be requisite to consider, First, what is the cause of fluidness; And this, I conceive, to be nothing else but a certain pulse or shake of heat; for Heat being nothing else but a very brisk and vehement agitation of the parts of a body (as I have elswhere made probable) the parts of a body are thereby made so loose from one another, that they easily move any way, and become fluid. That I may explain this a little by a gross Similitude, let us suppose a dish of sand set upon some body that is very much agitated, and shaken with some quick and strong vibrating motion, as on a Milstone turn’d round upon the under stone very violently whilst it is empty; or on a very stiff Drum-head, which is vehemently or very nimbly beaten with the Drumsticks. By this means, the sand in the dish, which before lay like a dull and unactive body, becomes a perfect fluid; and ye can no sooner make a hole in it with your finger, but it is immediately filled up again, and the upper surface of it levell’d. Nor can you bury a light body, as a piece of Cork under it, but it presently emerges or swims as ’twere on the top; nor can you lay a heavier on the top of it, as a piece of Lead, but it is immediately buried in Sand, and (as ’twere) sinks to the bottom. Nor can you make a hole in the side of the Dish, but the sand shall run out of it to a level, not an obvious property of a fluid body, as such, but this dos imitate; and all this meerly caused by the vehement agitation of the conteining vessel; for by this means, each sand becomes to have a vibrative or dancing motion, so as no other heavier body can rest on it, unless sustein’d by some other on either side: Nor will it suffer any Body to be beneath it, unless it be a heavier then it self.
Another Instance of the strange loosening nature of a violent jarring Motion, or a strong and nimble vibrative one, we may have from a piece of iron grated on very strongly with a file: for if into that a pin screw’d so firm and hard, that though it has a convenient head to it, yet it can by no means be unscrew’d by the fingers; if, I say, you attempt to unscrew this whilst grated on by the file, it will be found to undoe and turn very easily. The first of these Examples manifests, how a body actually divided into small parts, becomes a fluid. And the latter manifests by what means the agitation of heat so easily loosens and unties the parts of solid and firm bodies. Nor need we suppose heat to be any thing else, besides such a motion; for supposing we could Mechanically produce such a one quick and strong enough, we need not spend fuel to melt a body. Now, that I do not speak this altogether groundless, I must refer the Reader to the Observations I have made upon the shining sparks of Steel, for there he shall find that the same effects are produced upon small chips or parcels of Steel by the flame, and by a quick and violent motion; and if the body of steel may be thus melted (as I there shew it may) I think we have little reason to doubt that almost any other may not also. Every Smith can inform one how quickly both his File and the Iron grows hot with filing, and if you rub almost any two hard bodies together, they will do the same: And we know, that a sufficient degree of heat causes fluidity, in some bodies much sooner, and in others later; that is, the parts of the body of some are so loose from one another, and so unapt to cohere, and so minute and little, that a very small degree of agitation keeps them always in the state of fluidity. Of this kind, I suppose, the Æther, that is the medium or fluid body, in which all other bodies do as it were swim and move; and particularly, the Air, which seems nothing else but a kind of tincture or solution of terrestrial and aqueous particles dissolv’d into it, and agitated by it, just as the tincture of Cocheneel is nothing but some finer dissoluble parts of that Concrete lick’d up or dissolv’d by the fluid water.
And from this Notion of it, we may easily give a more Intelligible reason how the Air becomes so capable of Rarefaction and Condensation. For, as in tinctures, one grain of some strongly tinging substance may sensibly colour some hundred thousand grains of appropriated Liquors, so as every drop of it has its proportionate share, and be sensibly ting’d, as I have try’d both with Logwood and Cocheneel: And as some few grains of Salt is able to infect as great a quantity, as may be found by præcipitations, though not so easily by the sight or taste; so the Air, which seems to be but as ’twere a tincture or _saline substance, dissolv’d and agitated by the fluid and agil Æther, may disperse and expand_ it self into a vast space, if it have room enough, and infect, as it were, every part of that space. But, as on the other side, if there be but some _few grains_ of the liquor, it may extract all the colour of the tinging substance, and may dissolve all the Salt, and thereby become _much more impregnated_ with those substances, so may all the air that sufficed in a rarify’d state to fill some hundred thousand spaces of Æther, be compris’d in only one, but in a position proportionable dense. And though we have not yet found out such strainers for Tinctures and Salts as we have for the Air, being yet unable to separate them from their dissolving liquors by any kind of filtre, without præcipitation, as we are able to separate the Air from the Æther by Glass, and several other bodies.
And though we are yet unable and ignorant of the ways of præcipitating Air out of the Æther as we can Tinctures, and Salts out of several dissolvents; yet neither of these seeming impossible from the nature of the things, nor so improbable but that some happy future industry may find out ways to effect them; nay, further, since we find that Nature does really perform (though by what means we are not certain) both these actions, namely, by præcipitating the Air in Rain and Dews, and by supplying the Streams and Rivers of the World with fresh water, strain’d through secret subterraneous Caverns: And since, that in very many other proprieties they do so exactly seem of the same nature; till further observations or tryals do inform us of the contrary, we may _safely enough conclude_ them of the same kind. For it seldom happens that any two natures have so many properties coincident or the same, as I have observ’d Solutions and Air to have, and to be different in the rest. And therefore I think it neither impossible, irrational, nay nor difficult to be able to predict what is likely to happen in other particulars also, besides those which Observation or Experiment have declared thus or thus; especially, if the circumstances that do often very much conduce to the variation of the effects be duly weigh’d and consider’d. And indeed, were there not a probability of this, our inquiries would be endless, our tryals vain, and our greatest inventions would be nothing but the meer products of chance, and not of Reason; and, like Mariners in an Ocean, destitute both of a Compass and the sight of the Celestial guides, we might indeed, _by chance, Steer directly_ towards our desired Port, but ’tis _a thousand to one_ but we miss our aim. But to proceed, we may hence also give a plain reason, how the Air comes to be darkned by clouds, &c. which are nothing but a kind of precipitation, and how those precipitations fall down in Showrs. Hence also could I very easily, and I think truly, deduce the cause of the curious sixangular figures of Snow, and the appearances of Haloes, &c.
and the sudden thickning of the Sky with Clouds, and the vanishing and disappearing of those Clouds again; for all these things may be very easily imitated in a glass of liquor, with some slight Chymical preparations as I have often try’d, and may somewhere else more largely relate, but have not now time to set them down. But to proceed, there are other bodies that consist of particles more Gross, and of a more apt figure for cohesion, and this requires somewhat greater agitation; such, I suppose ☿, fermented vinous Spirits, several Chymical Oils, which are much of kin to those Spirits, &c. Others yet require a greater, as water, and so others much greater, for almost infinite degrees: For, I suppose there are very few bodies in the world that may not be made aliquatenus fluid, by some or other degree of agitation or heat.
Having therefore in short set down my Notion of a Fluid body, I come in the next place to consider what Congruity is; and this, as I said before, being a Relative property of a fluid, whereby it may be said to be like or unlike to this or that other body, whereby it does or does not mix with this or that body. We will again have recourse to our former Experiment, though but a rude one; and here if we mix in the dish _several kinds_ of sands, some of bigger, others of less and finer bulks, we shall find that by the agitation the fine sand will eject and _throw out_ of it self all those bigger bulks of small stones and the like, and those will be gathered together all into one place; and if there be other bodies in it of other natures, those also will be separated into a place by themselves, and united or tumbled up together. And though this do not come up to the highest property of Congruity, which is a Cohæsion of the parts of the fluid together, or a kind of attraction and tenacity, yet this does as ’twere shadow it out, and somewhat resemble it; for just after the same manner, I suppose the pulse of heat to agitate the small parcels of matter, and those that are of a _like bigness, and figure, and matter, will hold, or dance_ together, and those which are of a differing kind will be thrust or shov’d out from between them; for particles that are similar, will, like so many _equal musical strings equally stretcht, vibrate together in a kind of Harmony_ or unison; whereas others that are dissimilar, upon what account soever, unless the disproportion be otherwise counter-ballanc’d, will, like so many strings out of tune to those unisons, though they have the same agitating pulse, yet make quite differing kinds of vibrations and repercussions, so that though they may be both mov’d, yet are their vibrations so different, and so untun’d, as ’twere to each other, that they cross and jar against each other, and consequently, _cannot agree_ together, but fly back from each other to their similar particles.
Now, to give you an instance how the disproportion of some bodies in one respect, may be counter-ballanc’d by a contrary disproportion of the same body in another respect, whence we find that the subtil _vinous spirit_ is congruous, or does readily mix with water, which in many properties is of a very differing nature, we may consider that a unison may be made either by two strings of the same bigness, length, and tension, or by two strings of the same bigness, but of _differing length, and a contrary differing tension, or 3ly._ by two strings of unequal length and bigness, and of a differing tension, or of _equal length, and differing bigness_ and tension, and several other such varieties. To which three properties in strings, will correspond _three proprieties_ also in sand, or the particles of bodies, their Matter or Substance, their Figure or Shape, and their Body or Bulk. And from the varieties of these three, may arise infinite varieties in fluid bodies, though all agitated by the same pulse or vibrative motion. And there may be as many ways of making Harmonies and Discords with these, as there may be with musical strings. Having therefore seen what is the cause of Congruity or Incongruity, those relative properties of fluids, we may, from what has been said, very easily collect, what is the reason of those Relative proprieties also between fluid bodies and solid; for since all bodies consist of particles of such a Substance, Figure, and Bulk; but in some they are united together more firmly then to be loosened from each other by every vibrative motion (though I imagine that there is no body in the world, but that some degree of agitation may, as I hinted before, agitate and loosen the particles so as to make them fluid) those cohering particles may vibrate in the same manner almost as those that are loose and become unisons or discords, as I may so speak, to them.
