Micrographia Part 1

Micrographia.

by Robert Hooke.

PREFACE.

It is the great prerogative of Mankind above other Creatures, that we are not only able to _behold_ the works of Nature, or barely to _sustein_ our lives by them, but we have also the power of _considering_, _comparing_, _altering_, _a.s.sisting_, and _improving_ them to various uses. And as this is the peculiar priviledge of humane Nature in general, so is it capable of being so far advanced by the helps of Art, and Experience, as to make some Men excel others in their Observations, and Deductions, almost as much as they do Beasts. By the addition of such _artificial Instruments_ and _methods_, there may be, in some manner, a reparation made for the mischiefs, and imperfection, mankind has drawn upon it self, by negligence, and intemperance, and a wilful and superst.i.tious deserting the Prescripts and Rules of Nature, whereby every man, both from a deriv'd corruption, innate and born with him, and from his breeding and converse with men, is very subject to slip into all sorts of errors.

The only way which now remains for us to recover some degree of those former perfections, seems to be, by rectifying the operations of the _Sense_, the _Memory_, and _Reason_, since upon the evidence, the _strength_, the _integrity_, and the _right correspondence_ of all these, all the light, by which our actions are to be guided is to be renewed, and all our command over things it to be establisht.

It is therefore most worthy of our consideration, to recollect their several defects, that so we may the better understand how to supply them, and by what a.s.sistances we may _inlarge_ their power, and _secure_ them in performing their particular duties.

As for the actions of our _Senses_, we cannot but observe them to be in many particulars much outdone by those of other Creatures, and when at best, to be far short of the perfection they seem capable of: And these infirmities of the Senses arise from a double cause, either from the _disproportion of the Object to the Organ_, whereby an infinite number of things can never enter into them, or else from _error in the Perception_, that many things, which come within their reach, are not received in a right manner.

The like frailties are to be found in the _Memory;_ we often let many things _slip away_ from us, which deserve to be retain'd, and of those which we treasure up, a great part is either _frivolous_ or _false_; and if good, and substantial, either in tract of time _obliterated_, or at best so _overwhelmed_ and buried under more frothy notions, that when there is need of them, they are in vain sought for.

The two main foundations being so deceivable, it is no wonder, that all the succeeding works which we build upon them, of arguing, concluding, defining, judging, and all the other degrees of Reason, are lyable to the same imperfection, being, at best, either vain, or uncertain: So that the errors of the _understanding_ are answerable to the two other, being defective both in the quant.i.ty and goodness of its knowledge; for the limits, to which our thoughts are confin'd, are small in respect of the vast extent of Nature it self; some parts of it are _too large_ to be comprehended, and some _too little_ to be perceived. And from thence it must follow, that not having a full sensation of the Object, we must be very lame and imperfect in our conceptions about it, and in all the proportions which we build upon it; hence, we often take the _shadow_ of things for the _substance_, small _appearances_ for good _similitudes_, _similitudes_ for _definitions;_ and even many of those, which we think, to be the most solid definitions, are rather expressions of our own misguided apprehensions then of the true nature of the things themselves.

The effects of these imperfections are manifested in different ways, according to the temper and disposition of the several minds of men, some they incline to _gross ignorance_ and stupidity, and others to a _presumptuous imposing_ on other mens Opinions, and a _confident dogmatizing_ on matters, whereof there it no a.s.surance to be given.

Thus all the uncertainty, and mistakes of humane actions, proceed either from the narrowness and wandring of our _Senses_, from the slipperiness or delusion of our _Memory_, from the confinement or rashness of our _Understanding_, so that 'tis no wonder, that our power over natural causes and effects is so slowly improv'd, seeing we are not only to contend with the obscurity and _difficulty of the things_ whereon we work and think, but even the _forces of our own minds_ conspire to betray us.

These being the dangers in the process of humane Reason, the remedies of them all can only proceed from the _real_, the _mechanical_, the _experimental_ Philosophy, which has this advantage over the Philosophy of _discourse_ and _disputation_, that whereas that chiefly aims at the subtilty of its Deductions and Conclusions, without much regard to the first ground-work, which ought to be well laid on the Sense and Memory; so this intends the right ordering of them all, and the making them serviceable to each other.

The first thing to be undertaken in this weighty work, is a _watchfulness over the failings_ and an _inlargement of the dominion_, of the Senses.

To which end it is requisite, first, That there should be a _scrupulous_ choice, and a _strict examination_, of the reality, constancy, and certainty of the Particulars that we admit: This is the first rise whereon truth is to begin, and here the most severe, and most impartial diligence, must be imployed; the storing up of all, without any regard to evidence or use, will only tend to darkness and confusion. We must not therefore esteem the riches of our Philosophical treasure by the _number_ only, but chiefly by the _weight_; the most _vulgar_ Instances are not to be neglected, but above all, the most _instructive_ are to be entertain'd; the footsteps of Nature are to be trac'd, not only in her _ordinary course_, but when she seems to be put to her shifts, to make many _doublings_ and _turnings_, and to use some kind of art in indeavouring to avoid our discovery.

The next care to be taken, in respect of the Senses, is a supplying of their infirmities with _Instruments_, and, as it were, the adding of _artificial Organs_ to the _natural_; this in one of them has been of late years accomplisht with prodigious benefit to all sorts of useful knowledge, by the invention of Optical Gla.s.ses. By the means of _Telescopes_, there is nothing so _far distant_ but may be represented to our view; and by the help of _Microscopes_, there is nothing so _small_, as to escape our inquiry; hence there is a new visible World discovered to the understanding. By this means the Heavens are open'd, and a vast number of new Stars, and new Motions, and new Productions appear in them, to which all the ancient Astronomers were utterly Strangers. By this the Earth it self, which lyes so neer us, under our feet, shews quite a new thing to us, and in every _little particle_ of its matter; we now behold almost as great a variety of Creatures, as we were able before to reckon up in the whole _Universe_ it self.

It seems not improbable, but that by these helps the subtilty of the composition of Bodies, the structure of their parts, the various texture of their matter, the instruments and manner of their inward motions, and all the other possible appearances of things, may come to be more fully discovered; all which the ancient _Peripateticks_ were content to comprehend in two general and (unless further explain'd) useless words of _Matter_ and _Form_. From whence there may arise many admirable advantages, towards the increase of the _Operative_, and the _Mechanick_ Knowledge, to which this Age seems so much inclined, because we may perhaps be inabled to discern all the secret workings of Nature, almost in the same manner as we do those that are the productions of Art, and are manag'd by Wheels, and Engines, and Springs, that were devised by humane Wit.

In this kind I here present to the World my imperfect Indeavours; which though they shall prove no other way considerable, yet, I hope, they may be in some measure useful to the main Design of a _reformation_ in Philosophy, if it be only by shewing, that there it not so much requir'd towards it, any strength of _Imagination_, or exactness of _Method_, or depth of _Contemplation_ (though the addition of these, where they can be had, must needs produce a much more perfect composure) as a sincere _Hand_, and a _faithful_ Eye, to examine, and to record, the things themselves as they appear.

And I beg my Reader, to let me take the boldness to a.s.sure him, that in this present condition of knowledge, a man so qualified, as I have indeavoured to be, only with resolution, and integrity, and plain intentions of imploying his _Senses_ aright, may venture to compare the reality and the usefulness of his services, towards the true Philosophy, with those of other men, that are of much stronger, and more acute _speculations_, that shall not make use of the same method by the Senses.

The truth is, the Science of Nature has been already too long made only a work of the _Brain_ and the _Fancy_: It is now high time that it should return to the plainness and soundness of _Observations_ on _material_ and _obvious_ things. It is said of great Empires, That _the best way to preserve them from decay, is to bring them back to the first Principles, and Arts, on which they did begin_. The same is undoubtedly true in Philosophy, that by wandring far away into _invisible Notions_, has almost quite destroy'd it self, and it can never be recovered, or continued, but by returning into the same _sensible paths_, in which it did at first proceed.

If therefore the Reader expects from me any infallible Deductions, or certainty of _Axioms_, I am to say for my self, that those stronger Works of Wit and Imagination are above my weak Abilities; or if they had not been so, I would not have made use of them in this present Subject before me: Whenever he finds that I have ventur'd at any small Conjectures, at the causes of the things that I have observed, I beseech him to look, upon them only as _doubtful Problems_, and _uncertain ghesses_, and not as unquestionable Conclusions, or matters of unconfutable Science; I have produced nothing here, with intent to bind his understanding to an _implicit_ consent; I am so far from that, that I desire him, not absolutely to rely upon these Observations of my eyes, if he finds them contradicted by the future Ocular Experiments of other and impartial Discoverers.

As for my part, I have obtained my end, if these my small Labours shall be thought fit to take up some place in the large stock, of _natural Observations_, which so many hands are busie in providing. If I have contributed the _meanest foundations_ whereon others may raise n.o.bler _Superstructures_, I am abundantly satisfied; and all my ambition is, that I may serve to the great Philosophers of this Age, as the makers and the grinders of my Gla.s.ses did to me; that I may prepare and furnish them with some _Materials_, which they may afterwards _order_ and _manage_ with better skill, and to far greater advantage.

The next remedies in this universal cure of the Mind are to be applyed to the _Memory_, and they are to consist of such Directions as may inform us, what things are best to be _stor'd up_ for our purpose, and which is the best way of so _disposing_ them, that they may not only be _kept in safety_, but ready and convenient, to be at any time _produc'd_ for use, as occasion shall require. But I will not here prevent my self in what I may say in another Discourse, wherein I shall make an attempt to propose some Considerations of the manner of compiling a Natural and Artificial History, and of so ranging and registring its Particulars into Philosophical Tables, as may make them most useful for the raising of _Axioms_ and _Theories_.

The last indeed is the most _hazardous_ Enterprize, and yet the most _necessary_; and that is, to take such care that the _Judgment_ and the _Reason_ of Man (which is the third Faculty to be repair'd and improv'd) should receive such a.s.sistance, as to avoid the dangers to which it it by nature most subject. The Imperfections, which I have already mention'd, to which it is lyable, do either belong to the _extent_, or the _goodness_ of its knowledge; and here the difficulty is the greater, least that which may be thought a _remedy_ for the one should prove _destructive_ to the other, least by seeking to inlarge our Knowledge, we should render it weak, and uncertain; and least by being too scrupulous and exact about every Circ.u.mstance of it, we should confine and streighten it too much.

In both these the middle wayes are to be taken, nothing it to be_ omitted_, and yet every thing to pa.s.s a _mature deliberation_: No _Intelligence_ from Men of all Professions, and quarters of the World, to be _slighted_, and yet all to be so _severely examin'd_, that there remain no room for doubt or instability; much _rigour_ in admitting, much _strictness_ in comparing, and above all, much _slowness_ in debating, and _shyness_ in determining, is to be practised. The _Understanding_ is to _order_ all the inferiour services of the lower Faculties; but yet it is to do this only as a _lawful Master_, and not at a _Tyrant._ It must not _incroach_ upon their Offices, nor take upon it self the employments which belong to either of them. It must _watch_ the irregularities of the Senses, but it must not go before them, or _prevent_ their information. It must _examine_, _range_, and _dispose_ of the bank which it laid up in the Memory: but it must be sure to make _distinction_ between the _sober_ and _well collected heap_, and the _extravagant Ideas_, and _mistaken Images_, which there it may sometimes light upon. So many are the _links_, upon which the true Philosophy depends, of which, if any one be _loose_, or _weak_, the whole _chain_ is in danger of being dissolv'd; it is to _begin_ with the Hands and Eyes, and to _proceed_ on through the Memory, to be _continued_ by the Reason; nor is it to stop there, but to _come about_ to the Hands and Eyes again, and so, by a _continual pa.s.sage round_ from one Faculty to another, it is to be maintained in life and strength, as much as the body of man it by the _circulation_ of the blood through the several parts of the body, the Arms, the Feet, the Lungs, the Heart, and the Head.

If once this method were followed with diligence and attention, there is nothing that lyes within the power of human Wit (or which is far more effectual) of human Industry, which we might not compa.s.s; we might not only hope for Inventions to equalize those of _Copernicus_, _Galileo_, _Gilbert_, _Harvy_, and of others, whose Names are almost lost, that were the Inventors of _Gun-powder_, the _Seamans Compa.s.s_, _Printing_, _Etching_, _Graving_, _Microscopes_, &c. but mult.i.tudes that may far exceed them: for even those discoveries seem to have been the products of some such method, though but imperfect; What may not be therefore expected from it if thoroughly prosecuted? _Talking_ and _contention of Arguments_ would soon be turn'd into _labours_; all the fine _dreams_ of Opinions, and _universal metaphysical natures_, which the luxury of subtil Brains has devis'd, would quickly vanish, and give place to _solid Histories_, _Experiments_ and _Works._ And as at first, mankind _fell_ by _tasting_ of the forbidden Tree of Knowledge, so we, their Posterity, may be in part _restor'd_ by the same way, not only by _beholding_ and _contemplating_, but by _tasting_ too those fruits of Natural knowledge, that were never yet forbidden.

From hence the World may be a.s.sisted with _variety_ of Inventions, _new_ matter for Sciences may be _collected_, the _old improv'd_, and their _rust_ rubb'd away; and as it is by the benefit of Senses that we receive all our Skill in the works of Nature, so they also may be wonderfully benefited by it, and may be guided to an easier and more exact performance of their Offices; 'tis not unlikely, but that we may find out wherein our Senses are deficient, and as easily find wayes of repairing them.

The Indeavours of Skilful men have been most conversant about the a.s.sistance of the Eye, and many n.o.ble Productions have followed upon it; and from hence we may conclude, that there it a way open'd for advancing the operations, not only of all the other Senses, but even of the Eye it self; that which has been already done ought not to content us, but rather to incourage us to proceed further, and to attempt greater things in the same, and different wayes.

'Tis not unlikely, but that there may be yet invented several other helps for the eye, at much exceeding those already found, as those do the bare eye, such as by which we may perhaps be able to discover _living Creatures_ in the Moon, or other Planets, the _figures_ of the compounding Particles of matter, and the particular _Schematisms_ and _Textures_ of Bodies.

And as _Gla.s.ses_ have highly promoted our _seeing_, so 'tis not improbable, but that there may be found many _Mechanical Inventions_ to improve our other Senses, of _hearing_, _smelling_, _tasting_, _touching._ 'Tis not impossible to hear a _whisper_ a _furlongs_ distance, it having been already done; and perhaps the nature of the thing would not make it more impossible, though that furlong should be ten times multiply'd. And though some famous Authors have affirm'd it impossible to hear through the _thinnest plate_ of _Muscovy-gla.s.s_; yet I know a way, by which 'tis easie enough to hear one speak through a _wall a yard thick_. It has not been yet thoroughly examin'd, how far _Otocousticons_ may be improv'd, nor what other wayes there may be of _quickning_ our hearing, or _conveying_ sound through _other bodies_ then the _Air_: for that that it not the only _medium_, I can a.s.sure the Reader, that I have, by the help of a _distended wire_, propagated the sound to a very considerable distance in an _instant_, or with as seemingly quick a motion as that of light, at least, incomparably swifter then that, which at the same time was propagated through the Air; and this not only in a straight line, or direct, but in one bended in many angles.

Nor are the other three so perfect, but that _diligence_, _attention_, and many _mechanical contrivances_, may also highly improve them. For since the sense of _smelling_ seems to be made by the _swift pa.s.sage_ of the _Air_ (_impregnated_ with the steams and _effluvia_ of several odorous Bodies) through the grisly _meanders_ of the Nose whose surfaces are _cover'd_ with a very sensible _nerve_, and _moistned_ by a _transudation_ from the _processus mamillares_ of the Brain, and some adjoyning _glandules_, and by the moist _steam_ of the _Lungs_, with a Liquor convenient for the reception of those _effluvia_ and by the adhesion and mixing of those steams with that liquor, and thereby affecting the nerve, or perhaps by insinuating themselves into the juices of the brain, after the same manner, as I have in the following Observations intimated, the parts of Salt to pa.s.s through the skins of Effs, and Frogs. Since, I say, smelling seems to be made by some such way, 'tis not improbable, but that some contrivance, for making a great quant.i.ty of Air pa.s.s quick through the Nose, might at much promote the sense of smelling, as the any wayes hindring that pa.s.sage does dull and destroy it. Several tryals I have made, both of hindring and promoting this sense, and have succeeded in some according to expectation; and indeed to me it seems capable of being improv'd, for the judging of the const.i.tutions of many Bodies. Perhaps we may thereby also judge (as other Creatures seem to do) what is wholsome, what poyson; and in a word, what are the specifick properties of Bodies.

There may be also some other mechanical wayes found out, of sensibly perceiving the _effluvia_ of Bodies; several Instances of which, were it here proper, I could give of Mineral steams and exhalations; and it seems not impossible, but that by some such wayes improved, may be discovered, what Minerals lye buried under the Earth, without the trouble to dig for them; some things to confirm this Conjecture may be found in _Agricola_, and other Writers of Minerals, speaking of the Vegetables that are apt to thrive, or pine, in those steams.

Whether also those steams, which seem to issue out of the Earth, and mix with the Air (and so to precipitate some _aqueous_ Exhalations, wherewith 'tis impregnated) may not be by some way detected before they produce the effect, seems hard to determine; yet something of this kind I am able to discover, by an Instrument I contriv'd to shew all the minute variations in the pressure of the Air; by which I constantly find, that before, and during the time of rainy weather, the pressure of the Air is less, and in _dry weather_, but especially when an _Eastern Wind_ (which having past over vast tracts of Land is heavy with Earthy Particles) blows, it is much more, though these changes are varied according to very odd Laws.

The Instrument is this. I prepare a pretty capaceous Bolt-head AB, with a small stem about two foot and a half long DC; upon the end of this D I put on a small bended Gla.s.s, or brazen _syphon_ DEF (open at D, E and F, but to be closed with cement at F and E, as occasion serves) whose stem F should be about six or eight inches long, but the bore of it not above half an inch diameter, and very even; these I fix very strongly together by the help of very hard Cement, and then fit the whole Gla.s.s ABCDEF into a long Board, or Frame, in such manner, that almost half the head AB may lye buried in a concave Hemisphere cut into the Board RS; then I place it so on the Board RS, as is exprest in the first figure of the first Scheme; and fix it very firm and steady in that posture, so as that the weight of the _Mercury_ that is afterwards to be put into it, may not in the least shake or stir it; then drawing a line XY on the Frame RT, so that it may divide the ball into two equal parts, or that it may pa.s.s, as 'twere, through the center of the ball.

I begin from that, and divide all the rest of the Board towards UT into inches, and the inches between the 25 and the end E (which need not be above two or three and thirty inches distant from the line XY) I subdivide into Decimals; then stopping the end F with soft Cement, or soft Wax, I invert the Frame, placing the head downwards, and the Orifice E upwards; and by it, with a small Funnel, I fill the whole Gla.s.s with Quicksilver; then by stopping the small Orifice E with my finger, I oftentimes erect and invert the whole Gla.s.s and Frame, and thereby free the Quicksilver and Gla.s.s from all the bubbles or parcels of lurking Air; then inverting it as before, I fill it top full with clear and well strain'd Quicksilver, and having made ready a small ball of pretty hard Cement, by heat made very soft, I press it into the hole E, and thereby stop it very fast; and to secure this Cement from flying out afterward, I bind over it a piece of Leather, that is spread over in the inside with Cement, and wound about it while the Cement is hot: Having thus softned it, I gently erect again the Gla.s.s after this manner: I first let the Frame down edge-wayes, till the edge RV touch the Floor, or ly horizontal; and then in that edging posture raise the end RS; this I do, that if there chance to be any Air hidden in the small Pipe E, it may ascend into the Pipe F, and not into the Pipe DC: Having thus erected it, and hung it by the hole Q, or fixt it perpendicularly by any other means, I open the end F, and by a small _Syphon_ I draw out the _Mercury_ so long, till I find the surface of it AB in the head to touch exactly the line XY; at which time I immediately take away the _Syphon_, and if by chance it be run somewhat below the line XY, by pouring in gently a little _Mercury_ at F, I raise it again to its desired height, by this contrivance I make all the sensible rising and falling of the _Mercury_ to be visible in the surface of the _Mercury_ in the Pipe F, and scarce any in the head AB.

But because there really is some small change of the upper surface also, I find by several Observations how much it rises in the Ball, and falls in the Pipe F, to make the distance between the two surfaces an inch greater then it was before; and the measure that it falls in the Pipe is the length of the inch by which I am to mark the parts of the Tube F, or the Board on which it lyes, into inches and Decimals: Having thus justned and divided it, I have a large Wheel MNOP, whose outmost limb is divided into two hundred equal parts; this by certain small Pillars is fixt on the Frame RT, in the manner exprest in the Figure.

In the middle of this, on the back side, in a convenient frame, is placed a small Cylinder, whose circ.u.mference is equal to twice the length of one of those divisions, which I find answer to an inch of ascent, or descent, of _Mercury_: This Cylinder I, is movable on a very small Needle, on the end of which is fixt a very light Index KL, all which are so pois'd on the Axis, or Needle, that no part is heavier then another: Then about this Cylinder is wound a small Clew of Silk, with two small steel Bullets at each end of it GH; one of these, which is somewhat the heavier, ought to be so big, as freely to move to and fro in the Pipe F; by means of which contrivance, every the least variation of the height of the _Mercury_ will be made exceeding visible by the motion to and fro of the small Index KL.

But this is but one way of discovering the _effluvia_ of the Earth mixt with the Air; there may be, perhaps many others, witness the _Hygroscope_, an Instrument whereby the watery steams volatile in the Air are discerned, which the Nose it self is not able to find. This I have describ'd in the following Tract in the Description of the Beard of a wild Oat. Others there, are, may be discovered both by the Nose, and by other wayes also.

Thus the _smoak_ of burning _Wood_ is _smelt_, _seen_, and sufficiently _felt_ by the eyes: The _fumes_ of burning _Brimstone_ are _smelt_ and discovered also by the destroying the Colours of Bodies, as by the _whitening of a red Rose_: And who knows, but that the Industry of man, following this method, may find out wayes of improving this sense to as great a degree of perfection at it is in any Animal, and perhaps yet higher.

'Tis not improbable also, but that our _taste_ may be very much improv'd either by _preparing_ our taste for the Body, as, after eating _bitter_ things, _Wine_, or other _Vinous liquors_, are more sensibly tasted; or else by _preparing_ Bodies for our tast; as the dissolving of Metals with acid Liquors, make them tastable, which were before altogether insipid; thus _Lead_ becomes _sweeter_ then Sugar, and _Silver_ more _bitter_ then Gall, _Copper_ and _Iron_ of most _loathsome_ tasts. And indeed the business of this sense being to discover the presence of dissolved Bodies in Liquors put on the Tongue, or in general to discover that a fluid body has some solid body dissolv'd in it, and what they are; whatever contrivance makes this discovery improves this sense. In this kind the mixtures of Chymical Liquors afford many Instances; as the sweet Vinegar that is impregnated with Lead may be discovered to be so by the affusion of a little of an _Alcalizate solution_: The bitter liquor of _Aqua fortis_ and _Silver_ may be discover'd to be charg'd with that Metal, by laying in it some plates of Copper: 'Tis not improbable also, but there may be mult.i.tudes of other wayes of discovering the parts dissolv'd, or dissoluble in liquors; and what is this discovery but a kind of _secundary tasting_.

'Tis not improbable also, but that the sense of _feeling_ may be highly improv'd, for that being a sense that judges of the more _gross_ and _robust motions_ of the _Particles_ of _Bodies_, seems capable of being improv'd and a.s.sisted very many wayes. Thus for the distinguishing of _Heat_ and _Cold_, the _Weather-gla.s.s_ and _Thermometer_, which I have describ'd in this following Treatise, do exceedingly perfect it; by each of which the least variations of heat or cold, which the most Acute sense is not able to distinguish, are manifested. This is oftentimes further promoted also by the help of _Burning-gla.s.ses_, and the like, which collect and unite the radiating heat. Thus the _roughness_ and _smoothness_ of a Body is made much more sensible by the help of a _Microscope_, then by the most _tender_ and _delicate Hand_. Perhaps, a Physitian might, by several other _tangible_ proprieties, discover the const.i.tution of a Body as well as by the _Pulse_. I do but instance in these, to shew what possibility there may be of many others, and what probability and hopes there were of finding them, if this method were followed; for the Offices of the five Senses being to detect either the _subtil_ and _curious Motions_ propagated through all _pellucid_ or perfectly _h.o.m.ogeneous_ Bodies; Or the more _gross_ and _vibrative Pulse_ communicated through the _Air_ and all other convenient _mediums_, whether fluid or solid: Or the _effluvia_ of Bodies _dissolv'd_ in the _Air_; Or the _particles_ of bodies _dissolv'd_ or _dissoluble_ in _Liquors_, or the more _quick_ and _violent shaking motion_ of _heat_ in all or any of these: whatsoever does any wayes promote any of these kinds of _criteria_, does afford a way of improving some one sense.

And what a mult.i.tude of these would a diligent Man meet with in his inquiries? And this for the helping and promoting the _sensitive faculty_ only.

Next, as for the _Memory_, or _retentive faculty_, we may be sufficiently instructed from the _written Histories_ of _civil actions_, what great a.s.sistance may be afforded the Memory, in the committing to writing things observable in _natural operations_. If a Physitian be therefore accounted the more able in his Faculty, because he has had long experience and practice, the remembrance of which, though perhaps very imperfect, does regulate all his after actions: What ought to be thought of that man, that has not only a perfect _register_ of his own experience, but it grown _old_ with the experience of many hundreds of years, and many thousands of men.

And though of late, men, beginning to be sensible of this convenience, have here and there registred and printed some few _Centuries_, yet for the most part they are set down very lamely and imperfectly, and, I fear, many times not so truly, they seeming, several of them, to be design'd more for _Ostentation_ then _publique use_: For, not to instance, that they do, for the most part, omit those Experiences they have made, wherein their Patients have miscarried, it is very easie to be perceiv'd, that they do all along _hyperbolically extol_ their own Prescriptions, and vilifie those of others. Notwithstanding all which, these kinds of Histories are generally esteem'd useful, even to the ablest Physitian.

What may not be expected from the _rational_ or _deductive Faculty_ that is furnisht with such _Materials_, and those so readily _adapted_, and rang'd for use, that in a moment, at 'twere, thousands of Instances, serving for the _ill.u.s.tration_, _determination_, or _invention_, of almost any inquiry, may be _represented_ even to the sight? How neer the nature of _Axioms_ must all those _Propositions_ be which are examin'd before so many _Witnesses_? And how difficult will it be for any, though never so subtil an error in Philosophy, to _scape_ from being discover'd, after it has indur'd the _touch_, and so many other _tryals_?

What kind of mechanical way, and physical invention also is there requir'd that might not this may be found out? The _Invention_ of a way to find the _Longitude_ of places is easily perform'd, and that to as great _perfection_ as is desir'd, or to at great an _accurateness_ as the _Lat.i.tude_ of places can be found at Sea; and perhaps yet also to a greater certainty then that has been hitherto found, as I shall very speedily freely manifest to the world. The way of _flying_ in the Air seems princ.i.p.ally unpracticable, by reason of the _want of strength_ in _humane muscles_; if therefore that could be suppli'd, it were, I think, easie to make twenty contrivances to perform the office of _Wings_: What Attempts also I have made for the supplying that Defect, and my successes therein, which, I think, are wholly new, and not inconsiderable, I shall in another place relate.

'Tis not unlikely also, but that _Chymists_, if they followed this method, might find out their so much sought for _Alkahest_. What an _universal Menstruum_, which dissolves all sorts of _Sulphureous Bodies_, I have discover'd (which hat not been before taken notice of as such) I have shewn in the sixteenth Observation.

What a prodigious variety of Inventions in _Anatomy_ has this latter Age afforded, even in our own Bodies in the very _Heart_, by which we live, and the Brain, which is the seat of our knowledge of other things? witness all the excellent Works of _Pecquet_, _Bartholinus_, _Billius_, and many others; and at home, of Doctor _Harvy_, Doctor _Ent_, Doctor _Willis_, Doctor _Glisson_. In _Celestial Observations_ we have far exceeded all the Antients, even the _Chaldeans_ and _Egyptians_ themselves, whose _vast Plains_, _high Towers_, and _clear Air_, did not give them so great advantages over us, as have over them by our _Gla.s.ses_. By the help of which, they have been very much outdone by the famous _Galileo_, _Hevelius_, _Zulichem_; and our own Countrymen, Mr. _Rook_, Doctor _Wren_, and the great Ornament of our Church and Nation, the _Lord Bishop of Exeter_. And to say no more in _Aerial Discoveries_, there has been a wonderful progress made by the _n.o.ble Engine_ of _the most Ill.u.s.trious Mr.

Boyle_, whom it becomes me to mention with all honour, not only as my particular Patron, but as the _Patron_ of _Philosophy_ it self; which he every day _increases_ by his _Labours_, and _adorns_ by his _Example_.

The good success of all these _great Men_, and many others, and the now seemingly great _obviousness_ of most of their and divers other Inventions, which from the beginning of the world have been, as 'twere, trod on, and yet not minded till these last _inquisitive_ Ages (an Argument that there may be yet behind mult.i.tudes of the like) puts me in mind to recommend such Studies, and the prosecution of them by such methods, to the _Gentlemen_ of our Nation, whose _leisure_ makes them fit to _undertake_, and the _plenty_ of their fortunes _to accomplish_, extraordinary things in this way. And I do not only propose this kind of _Experimental Philosophy_ as matter of high _rapture_ and _delight_ of the mind, but even as a _material_ and _sensible Pleasure_. So vast it the _variety of Objects_ which will come under their Inflections, so many _different wayes_ there are _of handling_ them, so great is the _satisfaction_ of _finding_ out _new things_, that I dare compare the _contentment_ which they will injoy, not only to that of _contemplation_, but even to that which most men prefer of _the very Senses themselves_.

And if they will please to take any incouragement from so mean and so imperfect endeavours as mine, upon my own experience, I can a.s.sure them, without arrogance, That there has not been any inquiry or Problem in _Mechanicks_, that I have hitherto propounded to my self, but by a certain method (which I may on some other opportunity explain) I have been able presently to examine the possibility of it; and if so, as easily to excogitate divers wayes of performing it: And indeed it is possible to do as much by _this method_ in _Mechanicks_, as by _Algebra_ can be perform'd in _Geometry_. Nor can I at all doubt, but that the same method is as applicable to _Physical Enquiries_, and as likely to find and reap thence at plentiful a crop of Inventions; and indeed there seems to be no subject so barren, but may with this good husbandry be highly improv'd.

Toward the prosecution of this method in _Physical Inquiries_, I have here and there _gleaned_ up an _handful_ of Observations, in the collection of most of which I made use of _Microscopes_, and some other _Gla.s.ses_ and _Instruments_ that improve the sense; which way I have herein taken, not that there are not mult.i.tudes of useful and pleasant Observables, yet uncollected, obvious enough without the helps of Art, but only to promote the use of Mechanical helps for the Senses, both in the surveying the already visible World, and for the discovery of many others. .h.i.therto unknown, and to make us, with the great Conqueror, to be affected that we have not yet overcome one World when there are so many others to be discovered, every considerable improvement of _Telescopes_ or _Microscopes_ producing new Worlds and _Terra-Incognita's_ to our view.

The Gla.s.ses I used were of our English make, but though very good of the kind, yet far short of what might be expected, could we once find a way of making Gla.s.ses Elliptical, or of some more true shape; for though both _Microscopes_, and _Telescopes_, as they now are, will magnifie an Object about a thousand thousand times bigger then it appears to the naked eye; yet the Apertures of the Object-gla.s.ses are so very small, that very few Rays are admitted, and even of those few there are so many false, that the Object appears _dark_ and _indistinct_: And indeed these inconveniences are such, as seem inseparable from Spherical Gla.s.ses, even when most exactly made; but the way we have hitherto made use of for that purpose is so imperfect, that there may be perhaps ten wrought before one be made tolerably good, and most of those ten perhaps every one differing in goodness one from another, which is an Argument, that the way hitherto used is, at least, very uncertain. So that these Gla.s.ses have a double defect; the one, that very few of them are exactly true wrought; the other, that even of those that are best among them, none will admit a sufficient number of Rayes to magnifie the Object beyond a determinate bigness. Against which Inconveniences the only Remedies I have hitherto met with are these.

First, for _Microscopes_ (where the Object we view is near and within our power) the best way of making it appear bright in the Gla.s.s, is to cast a great quant.i.ty of light on it by means of _convex gla.s.ses_, for thereby, though the aperture be very small, yet there will throng in through it such mult.i.tudes, that an Object will by this means indure to be magnifi'd as much again as it would be without it. The way for doing which is this. I make choice of some Room that has only one window open to the South, and at about three or four foot distance from this Window, on a Table, I place my _Microscope_, and then so place either a round Globe of Water, or a very deep clear_ plano convex_ Gla.s.s (whose convex side is turn'd towards the Window) that there is a great quant.i.ty of Rayes collected and thrown upon the Object: Or if the Sun shine, I place a small piece of oyly Paper very near the Object, between that and the light; then with a good large Burning-Gla.s.s I so collect and throw the Rayes on the Paper, that there may be a very great quant.i.ty of light pa.s.s through it to the Object; yet I so proportion that light, that it may not singe or burn the Paper. Instead of which Paper there may be made use of a small piece of Looking-gla.s.s plate, one of whose sides is made rough by being rubb'd on a flat Tool with very find sand, this will, if the heat be leisurely cast on it, indure a much greater degree of heat, and consequently very much augment a convenient light. By all which means the light of the Sun, or of a Window, may be so cast on an Object, as to make it twice as light as it would otherwise be without it, and that without any inconvenience of glaring, which the immediate light of the Sun is very apt to create in most Objects; for by this means the light is so equally diffused, that all parts are alike inlightned; but when the immediate light of the Sun falls on it, the reflexions from some few parts are so vivid, that they drown the appearance of all the other, and are themselves also, by reason of the inequality of light, indistinct, and appear only radiant spots.