An ATTEMPT FOR THE EXPLICATION Of the PHAENOMENA, Observable in an Experiment Published by the Honourable ROBERT boil, Esq In the XXXV. Experiment of his Epistolical Discourse touching the AIR. In Confirmation of a former Conjecture made by R. H.  Nos cum non semper magna referre possimus, vera tamen sed rara recitamus; neque enim minori miraculo in parvis Natura ludit quam in magnis, Cardan de Vari. L. 8. Cap. 43. Tum vero de Scientiarum progressu spes bene fundabitur, quum in historiam naturalem recipientur & aggregabuntur complura experimenta, quae in se nullius sunt usus, sed ad inventionem causarum & axiomatum tan●um faciunt, Verulamii Nou. Org. Aph. 99 
LONDON, Printed by J. H. for Sam. Thomson at the Bishop's Head in St. Paul's Churchyard, 1661.   

To the Honourable Robert boil, Esq  
Sir,  
THe honour you were pleased to do me, in putting me upon this enquiry, did not a little animate and encourage me to persevere in what I had begun with so happy an Omen. My good Success therefore herein, if any, is wholly to be ascribed to yourself; as being the first Excitor and chief Abettor of it. And therefore I hope that may be my excuse, for craving You so great a Patron thereunto, in that I could not have entitled it to any other without a manifest Injury to Your Honour; whose Gracious countenancing of it, justly requires my utmost Gratitude. I must therefore with the Persian offer to you, as he to the Sun, what he believes himself to have received from it. And therefore I trust my endeavouring to soar aloft with the Eagle, to enjoy the Influence of the most Glorious Light of the world, will find a Pardon, and be judged much better, than a hover and fluttering with the silly Fly about the dim and fading Flame of a candle, that at best, will but sing those wings that raised it so high, and in stead of giving it more Vigour, will wholly disinable it for the like Future Attempts. I am not a little sensible indeed, that the Minuteness both of the thing and its Author, may seem to make it a Present very unfit for so great a Personage. But yet I am in hope, that like the poor man, that seeing many Noble and Rich, hasting to meet Artaxerxes, with their Splendid and Sumptuous Gifts, would needs carry something too, and though 'twas but a little water fetched out of the River in the Palms of his Hands, yet addressing himself, he presented it with an unexpected acceptance, I also may be happy in the like success, with this Oblation, which is but a few drops taken out of the River (as I may so speak) of the Phaenomena of Nature (which passes by, and is scarce regarded by any, though free for all) that is, some few observations, which though but mean and obvious, yet I think scarce diligently taken notice of by any; and though jumbled together in a careless, if any Method, yet the best I had leisure to throw it into. And though delivered in a Style nothing elegant, yet I hope (which was my greatest aim) it may serve (with your favourable construction of it) to signify the desire I have of expressing myself most affectionately to be  
Sir, Your Honours most Faithful and most Humble Servant, Robert Hooke.   

The Experiment, as I find it set down in the forementioned Epistle, runs thus;  
AN Eminent Mathematician told me one day, that some inquisitive Frenchmen (whose Names I know not) had observed, that in case one end of a slender and perforated Pipe of Glass, as A. B. or C. be dipped in water, as in that contained in the Vessel, G. H. of the 8th. Figure, the Liquor will ascend to some ' height in the Pipe, as to D. E. or F. though held perpendicular to the plain of the water. And to satisfy me, that he mis-related not the Experiment, he soon after brought two or three small Pipes of Glass, which gave me the opportunity of trying it, though I had the less reason to distrust it, because I remember I had often in the long and slender Pipes of some Weather-Glasses, which I had caused to be made after a somewhat peculiar fashion, taken notice of the like ascension of the Liquor, though (presuming it might be casual) I had made but little reflection upon it. But after this trial, beginning to suppose, that though the water in these Pipes that were brought me, rise not above a quarter of an Inch (if near so high) yet, if the Pipes were made slender onough, the water might rise to a very much greater height; I caused several of them to be, by a dexterous hand, drawn out at the flame of a Lamp, in one of which that was almost incredibly slender, we found that the water ascended (as it were of itself) five Inches by measure, to the no small wonder of some famous Mathematicians, who were Spectators of some of these Experiments And this height the Water reached to, though the Pipe were held in as erected a posture as we could: For if it were inclined, the water would fill a greater part of it, though not rise higher in it▪ And we also found, that when the inside of the Pipe was wetted beforehand, the water would rise much better than otherwise: but we caused not all our slender Pipes to be made strait, but some of them crooked, like Syphons: And having immersed the shorter Leg of one of these into a Glass that held some fair water, we found as we expected, that the water arising to the top of the Syphon, though that were high enough, did of itself run down the longer Leg, and continue running like an ordinary Syphon. The cause of this ascension of the water, appeared to all that were present, so difficult, that I must not stay to enumerate the various Conjectures that were made at it, much less to examine them; especially having nothing but bare Conjectures to substitute in the room of those I do not approve. We tried indeed, by conveying a very slender Pipe and a small Vessel of water into our Engine, whether or no the Exsuction of the ambient Air would assist us to find the cause of the ascension we have been speaking of: But though we employed red Wine in stead of water, yet we could scarce certainly perceive through so much Glass, as was interposed betwixt our eyes and the Liquor, what happened in a Pipe so slender, that the redness of the Wine was scarce sensible in it. But as far as we could discern, there happened no great alteration to the Liquor: which seemed the less strange, because the Spring of that Air that might depress the water in the Pipe, was equally debilitated with that which remained to press upon the Surface of the Water in the little Glass. Wherefore, in favour of his ingenuous Conjecture, who ascribed the Phaenomenon, under consideration to the greater pressure made upon the water by the Air without the Pipe, than by that within it, (where so much of the water (consisting perhaps of Corpuscles more pliant to the internal surfaces of the glass) was contiguous to the sides) it was shown, that in case the little Glass-Vessel that held the water, of which a part ascended into the slender Pipe, were so closed, that a man might with his mouth suck the Air out of it, the water would immediately subside in the small Pipe. And this would indeed infer, that it asscended before only by the pressure of the incumbent Air. But that it may (how justly I know not) be objected, that peradventure this would not happen, in case the upper end of the Pipe were in a vacuum: And that 'tis very probable the water may subside, not because the pressure of the internal Air is taken off by exsuction, but by reason of the spring of the external Air, which impels the water it finds in its way to the Cavity deserted by the other Air, and would as well impel the same water upwards, as make it subside, if it were not for the accidental posture of the Glasses. However, having not now leisure to examine any further this Matter, I shall only mind your Lordship, that if You will prosecute this Speculation, it will be pertinent to find out likewise, Why the surface of Water (as is manifest in Pipes) uses to be concave, being depressed in the middle, and higher on every side? and why in Quicksilver on the contrary, not only the surface is wont to be very convex, or swelling, in the middle; but if you dip the end of a slender Pipe in it, the surface of the Liquor (as 'tis called) will be lower within the Pipe, than without. Which Phaenomena, whither, and how far, they may be deduced from the Figure of the Mercurial Corpuscles, and the Shape of the Springy Particles of the Air, I willingly leave to be considered.   

An Attempt for the Explication of this New Experiment.  
MY former 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 A. B. C. than 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 waters Surfaces.  
And the Second is, That in this Experiment there is such an unequal pressure.  
Now 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 a quantity of Water, suppose enough to fill it as high as the Line A. B. and applying your mouth to one end, as to D. you shall find, that by gently blowing in at it, you shall depress the Superficies B. and thereby raise the opposite Superficies A. to a considerable distance; and by gently sucking, you may perceive the clean contrary effects produced.  
Next, That there is such an unequal pressure, I shall prove from this, that there is a much greater inconformity or incongruity (call it what you please) of Air to Glass, and some other Bodies, than there is of Water to the same.  
What I mean hereby, I shall in short explain, by defining conformity or congruity to be a property of a fluid Body, whereby any part of it is readily united or intermingled with any other part, either of itself, or of any other Homogeneal or Similar, fluid, or firm and solid body: And unconformity or incongruity to be a property of a fluid, by which it is kept off and hindered from uniting or mingling with any heterogeneous or 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 Chemical Spirits and Oils 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 be brought to mix) we need seek no further for Examples of this kind, than 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 Salad Oil swimming upon water: In all which, and many more Examples that might be enumerated, of this sort, the incongruity of two fluids is easily discernible. And as for examples of Congruity or Incongruity of Liquids' one with another, or with several kinds of firm, or solid Bodies, they have long since been taken notice of, and called by the Names of Drieness and Moisture, (though these two Names are not comprehensive enough, they being commonly used to signify 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 than others; and that water let fall upon a Feather, the whiter side of a Colwort, and some other leaves, or upon almost any unctuous or resinous superficies, etc. will not at all adhere to them, but easily tumble off from them, like a solid Bowl; whereas if dropped upon Linen, Paper, Day, green Wood, etc. it will not be taken off, without leaving some part of it behind adhering to them: So Quicksilver, which will very hardly be brought to stick to any vegetable body, will readily adhere to, and mingle with several clean metalline bodies.  
Now from what cause this congruity or Incongruity of bodies one to another, does proceed, whether from the Figure of their constituent Particles, or interspersed pores, or from the differing motions of the parts of the one and the other, as whether circular, undulating, progressive, etc. whether I say from one, or more, or none of these enumerated causes, I shall not here determine; It being an enquiry more proper to be followed and explained among the general Principles of Philosophy, whither at present I shall refer it; as fearing lest it might here seem absurd, without the concatenation of several other Principles to explicate it; and knowing it likewise sufficient for this enquiry to show, that there is such a property, from what cause soever it proceeds.  
These Properties therefore (always the concomitants of fluid bodies) produce these following visible Effects:  
First, They unite the parts of a fluid to its homogeneal Solid, or keep them separate from its heterogeneal: Hence Quicksilver will (as we noted before) stick to Gold, Silver, Tin, Led, etc. and unite with them: but roll off from wood, stone, glass, if never so little situated out of its horizontale Paralelisme; and water that will wet salt and dissolve it, will slip off from Tallow, or the like, without at all adhering; as it may likewise be observed to do, upon a dusty superficies. And next they cause the parts of homogeneal fluid bodies readily to adhere together and mix, and of heterogeneal, to be exceeding averse thereunto. Hence we find, that two small drops of water, on any superficies they can roll on, will, if they chance to touch each other, readily unite and mix in one 3d. Globule or drop: the like may be observed with two small Bowls of Quicksilver upon a Table or Glass, provided the surfaces of those Globule be not dusty; and with two drops of Oil upon fair water, etc. And further, water put unto wine, salt water, Vinegar, spirit of wine, or the like, does immediately (especially if they be shaken together) disperse itself all over them: hence on the contrary also we find, that water poured upon Quicksilver, and Oil upon that water, and Air upon that Oil, though they be stopped closely up into a Bottle, and shaken never so much, they will by no means long suffer any of their bigger parts to be united or included within any of the other Liquors (by which recited Liquors, may be plainly enough represented the 4 Peripaterical Elements.) From this property 'tis that a drop of water does not mingle with, or vanish into Air, but is driven (by that fluid equality protruding it on every side) and forced into as little a space as it can possibly be contained in, namely, into a Round Globule. So likewise a little air blown under the water, is united or thrust into a Bubble, by the ambient water. And a parcel of Quicksilver enclosed with Air, water, or almost any other liquor, is form into a round Ball.  
Now the cause why all these included fluids newly mentioned, or as many others as are wholly included within a heterogeneous fluid, are not exactly of a spherical Figure (seeing that if caused by these Principles only, it could be of no other) must proceed from some other kind of pressure against the two opposite flatted sides. This adventitious or accidental pressure may proceed from divers causes, and accordingly must diversify the Figure of the included heterogeneous fluid: For seeing that a body may be included either with a fluid only, or only with a solid, or partly with a fluid and partly with a solid, or partly with one fluid, and partly with another, there will be found a very great variety of the terminating surfaces, much differing from a Spherical, according to the various resistance or pressure that belongs to each of these encompassing mediums.  
Which Properties may in general be deduced from two heads, viz. Motion, and Rest. For either this Globular Figure is altered by a natural Motion, such as is Gravity, or a violent, such as i● any accidental motion of the fluids, as we see in the wind ruffling up the water, and the purl of Streams, and foaming of Cartaracts, and the like, which because they are so obvious and easily understood, and so little pertinent to our present enquiry, I shall refer to some other intended Speculations, to which they do more properly belong. Or thirdly, By the Firmness and Stability of the ambient Solid. For if the including Solid be of an angular or any other irregular Form, the included fluid will be near of the like, as a Pint Pot full of water, or a Bladder full of Air. And next, if the including or included fluid have a greater gravity one than another, then will the globular Form be depressed into an Eliptico-spherical: As if for example, we suppose the Circle A. B. C. D. in the first Figure, to represent a drop of water, Quicksilver or the like, included with the Air, or the like, which supposing there were no gravity at all in either of the fluids, or that the contained and containing were of the same weight, would be equally depressed into an exactly-spherical body (the ambient pressing equally against every side of it▪) But supposing either a greater gravity in the included, by reason whereof the parts of it being pressed from A. towards B. and thereby the whole put into motion, and that motion being hindered by the resistance of the subjacent parts of the ambient, the globular Figure, A. D. B. C. will be depressed into the Eliptico-spherical, E. G. F. H. For the side A. is detruded to E. by the Gravity, and B. to F. by the resistance of the subjacent medium: and therefore C. must necessarily be thrust to G. and D. to H. Or else supposing a greater gravity in the ambient, by whose more than ordinary pressure against the under side of the included globul, B. will be forced to F. & by its resistance of the motion upwards, the side A. will be depressed to E. and therefore C. being thrust to G. & D. to H. the globular Figure by this means also will be made an Eliptico-spherical. Next if a fluid be included partly with one, and partly with another fluid, it will be found to be shaped diversely, according to the proportion of the gravity and incongruity of the 3 fluids one to another, as in the second Figure, let the upper M M M be Air, the middle L. M. N. O be common Oil, the lower O. O. O. be water, the Oil will be formed not into a spherical Figure, such as is represented by the pricked Line, but into such a Figure as L. M. N. O. whose side L. M. N. will be of a flatter Eliptical Figure, by reason of the great disproportion between the Gravity of Oil and Air, and the side L. O. M. of a rounder, because of the smaller difference between the weight of Oil and water. Lastly, The globular Figure will be changed, if the ambient be partly fluid and partly solid. And here the termination of the encompassed fluid towards the encompassing is shaped according to the proportion of the congruity or incongruity of the fluids to the solids, and of the gravity and incongruity of the fluids one to another. As suppose the subjacent medium that hinders an included fluid's descent, be a solid, as let K. L. in the first Figure represent the smooth superficies of a Table, E. G. F. H. a parcel of running Mercury, the side G. F. H. will be more flatted, according to the proportion of the incongruity of the Mercury and Air to the Wood, and of the gravity of Mercury and Air one to another; The side G. E. H. will likewise be a little more depressed by reason the subjacent parts are now at rest which were before in motion [I have not here time, nor is it much to my present purpose, to show how much the Figure of the descending fluid may be altered from this Eliptico spherical Figure, by a very small resistance of the subjacent medium, for the advantage the under parts of the descendent may have as to the acceleration of their motions of descent, may be able to draw them out into the Form of the Figure X.] Or further in the 3d. Figure, let A. I. L. D. represent an including solid medium of a cylindrical shape (as suppose a small Glass Jar) Let F. G. E. M. represent a contained fluid, as water; this towards the bottom and sides, is figured according to the concavity of the Glass: But its upper Surface, which by reason of its gravity, (not considering at all the Air above it, and so neither the congruity or incongruity of either of them to the Glass) should be terminated by part of a Sphere whose diameter should be the same with that of the earth, which to our sense would appear a strait Line, as F. G▪ E. Or which by reason of its having a greater congruity to Glass than Air has, (not considering its Gravity) would be thrust into a concave Sphere, as C. H. B. whose diameter would be the same with that of the concavity of the Vessel. But by reason of its having a greater gravity than the Air, and having likewise a greater congruity to Glass, than the Air has; from hence I say it is terminated, by a concave Eliptico-spherical Figure, as C. K. B. For by its congruity it easily conforms itself, and adheres to the Glass, and constitutes as 'twere one containing body with it, and therefore should thrust the contained Air on that side it touches it, into a spherical Figure, as B. H. C. but the motion of Gravity depressing a little the Corners B. and C. reduces it into the aforesaid Figure, C. K. B. Now that 'tis the greater congruity of one of the two contiguous fluids, than of the other, to the containing solid, that causes the separating surfaces of the two liquids to be thus or thus figured: And that 'tis not because this or that figurated surface is more proper, natural or peculiar to one of these fluid bodies, than to the other, will appear from this, that the same fluids will by being put into differing solids, change their surfaces for the same water, which in a Glass or wooden Vessel will have a concave surface upwards, and will rise higher in a smaller than greater Pipe, the same water, I say, in the same Pipes greased over or oiled, will produce quite contrary effects, for it will have a protuberant and convex surface upwards, and will not rise so high in small, as in bigger Pipes: Nay, in the very same solid Vessel, you may make the very same two contiguous Liquids to alter their Surfaces; for taking a small Wine-Glass, or such like Vessel, and pouring water gently into it, you shall perceive the surface of the water all the way concave, till it rise even with the top, when you shall find it (if you gently and carefully pour in more) to grow very protuberant and convex; the reason of which is plain, for that the solid sides of the containing body are no longer extended, to which the water does more readily adhere, than the air; but it is henceforth to be included with air, which would reduce it into a hemisphere, but by reason of its gravity, it is flatted into an Oval. Quicksilver also which to Glass is more incongruous than Air (and thereby being put into a Glass-Pipe, will not adhere to it, but by the more congruous air will be forced to have a very protuberant surface, and to rise higher in a greater than a lesser Pipe) this Quicksilver to clean Metal, especially to Gold, Silver, Tin, Led, etc. Iron excepted, is more congruous than Air, and will not only stick to it, but have a concave Surface like water, and rise higher in a less, than in a greater Pipe.  
In all these Examples, 'tis evident, that there is an extaordinary and adventitious force by which the globular Figure of the contained heterogeneous fluid is altered, neither can it be imagined, how it should otherwise be of any other Figure than Globular: For being by the heterogeneous fluid equally protruded every way, whatsoever part is protuberant, will be thereby depressed. From this cause it is that in its effects it does very much resemble a round Spring (such as a Hoop) I shall not here speak of the nature of Springs in general, as being more proper for another Discourse, but only take notice, that as in a round Spring there is required an additional pressure against two opposite sides, to reduce it into an Oval Form, or to force it in between the sides of a Hole whose Diameter is less than that of the Spring, there must be a considerable force or protrusion against the concave or inner side of the Spring, ●o to alter this spherical constitution of an included fluid body, there is required more pressure against opposite sides to reduce it into an Oval, and to press it into an Hole less in Diameter than itself, it requires a greater protrusion against all the other sides. What degrees of force are requisite to reduce them into longer and longer Ovals, or to press them into less and less holes, I have not yet experimentally calculated; but thus much by experiment I find in general, that there is always required a greater pressure to close them into longer Ovals, or protrude them into smaller holes: the necessity and reason of this, were it requisite, I could easily explain: but being not so necessary, and requiring more room and time than I have for it at present, I shall here omit it; and proceed to show, that this may be presently found true, if Experiment be made with a Round Spring (the way of which trials can scarce be missed by any one, at all conversant in Experiments▪) And with the fluid bodies of Mercury, Air, etc. the way of trying, which will be somewhat more difficult; and therefore I shall in brief describe it. He therefore that would try with Air, must first be provided of a Glass-Pipe, made of the shape of that in the fifth Figure, whereof of the side A. B. represents a strait Tube of about 3 foot long (C. D.) represents an other part of it, which consists of C. E. F. G. D. etc. several round Bubbles so ordered, that there is left a passage out of each of them, into its next, of which passages, that between C. and E. is to be the biggest; (as for example, ⅙ of an Inch in Diameter) that between E. and F. is to be less, (viz. ⅛ of an Inch) that between F. and G. (1/12 of an Inch) that between G. and D. (1/16) that above D (1/24 or half a Line) there may be added as many more as the experimenter shall think fit, with passages or interjacent holes continually decreasing by known quantities so far as his senses are able to help him; I say so far, because there may be made Pipes so small that it will be impossible to perceive the perforation with ones naked eye, though by the help of a Microscope, it may easily enough be perceived: Nay, I have made a Pipe perforated from end to end, so small, that with your naked eye you would very hardly have seen the body of it, insomuch that I have been able to knit it up into a knot without breaking, but this by the by.  
To proceed then, for the trial of the Experiment, the Experimenter must place the Tube (A. B.) perpendicular, and fill the Bubble E. with the passage beneath it, full of water, but leave the bubble C. full of Air, and then gently pouring in water into the Pipe A. B. he must observe diligently how high the water will rise in it before it protrude the Bubble of Air, (C.) through the narrow passage into E. and denote exactly the height of the Cylinder of water, then filling the bubble F. with water and E. with air, he may proceed as formerly, denoting likewise the height of the Cylinder of water, able to protrude the Bubble E. through the passage E. F. the like may be do with the next passage, and the next, etc. as far as he is able, then comparing the several heights of the Cylinders, with the several holes through which each Cylinder did force the air (having due regard to the Cylinders of water in the Tube C. D) it will be very easy to determine, what force is requisite to press the Air into such and such a hole, or (to apply it to our present experiment) how much of the pressure of the Air is taken off by its ingress into smaller and smaller holes. Now because to prepare this Instrument, is something difficult (by reason of the holes which will be found very troublesome to be measured) it will be better to prepare small Glass-Pipes, such as F. G. H. I. K. L. of the several Boars desired, each of them about an Inch long, and having a Pipe, (such as is described in the 5th. Figure) with only one Bubble, as (C) with the passage (C. E) and proceeding as before, to force the Air first through that; then to fasten into it with Cement the next smaller Pipe, and try with it as with the other; then a less, and so to the least, denoting, comparing, and collecting as before. From these, and other such trials, it will be found very evident, that to force the air or other fluid into a smaller hole, of an incongruous Solid, there is required a greater force, than there is requisite for the protrusion of it into a bigger. Come we therefore to the explanation of the Phaenomena, in the experiment of the rising of water in a smaller Pipe; And from the application of what has been said to the entering of the Air into the bigger hole of the Vessel and▪ into the smaller hole of the Pipe, we shall clearly find, that there is a greater pressure of the air upon the water in the Vessel or greater Pipe, than there is upon that in the Lesser Pipe: For since the pressure of the air every way is found to be as much as is able to press up and sustain a Cylinder of Quicksilver of two foot and a half high, or thereabouts; And since of this pressure so many more degrees are required to force the Air into a smaller than into a greater hole, that is full of a more congruous fluid. And lastly, since those degrees that are requisite to press it in, are thereby taken off from the Air within, and the Air within left with so many degrees of pressure less than the Air without; it will follow, that the Air in the less Tube or Pipe, will have less pressure against the superficies of the water therein, than the Air in the bigger: which was the minor Proposition to be proved.  
The Conclusion therefore will necessarily follow, viz.  
That this unequal pressure of the Air caused by its protrusion into unequal holes, is a cause sufficient to produce this effect, without the help of any other concurrent, and therefore is the principal, (if not the only) cause of this Phaenomenon.  
This therefore being thus explained, there will be divers Phaenomena explicable thereby, as, the Rising of Liquors in a Filtre, the rising of Spirit of Wine, Oil, Melted Tallow, etc. in the Weak of a Lamp, (though made of small Wire, Threads of Asbestus, Strings of Glass, or the like) the Rising of Liquors in a Sponge, piece of Bread, perhaps also the ascending of the Sap in Trees and Plants, through their small, and some of them imperceptible Pores, (of which perhaps I may say more on another occasion) at least the passing of it out of the earth into their roots. I know not also whether it will be requisite to add what things occurred to my thoughts, when I had these Phaenomena under consideration; which I shall only propound as Queries, that may serve as hints to some further discovery, and not as Axioms.  
In short, they were these;  
First, Upon the consideration of the congruity and incongruity of Bodies, as to touch, I found also the like congruity and incongruity (if I may so speak) as to the Transcursion of the Rays of Light: For in this regard, water (not now to mention other Liquors) seems nearer of affinity to glass than Air, and Air than▪ Quicksilver: For an oblique Ray out of Glass, will pass into water with very little refraction from the perpendicular, but none out of Glass into Air, excepting a direct, will pass without a very great refraction from the perpendicular, nay any oblique Ray under 30 degrees, will not be admitted into the Air at all, but reflected. And Quicksilver will neither admit oblique or direct, but reflect all; so that Quicksilver as to the transmitting of the Rays of Light, seems to be of a quite differing constitution, from that of Air, Water, Glass, etc. and to assimilate most those opacous and strong reflecting bodies of Metals: and as to the property of cohesion or congruity, it seems to keep the same order.  
A Second thing (which was hinted to me, by the consideration of the included fluid's globular form, caused by the protrusion of the ambient heterogeneous fluid) was whether the Phaenomena of gravity might not by this means be explained, by supposing the Globe of Earth, Water and Air to be included with a fluid, heterogenous to all and each of them, which is so subtle, as not only to be every where interspersed through the Air, (or rather the air through it) but does pervade the bodies of Glass, and even the closest Metals, by which means it does endeavour to detrude all earthly bodies as far from it as it can; and partly thereby, and partly by other of its properties (of which I may some other time give a fuller account) move them towards the Centre of the Earth. Now that there is some such fluid, I could produce many experiments and Reasons, that do seem to prove. But because I see it would ask some time and room to set them down and explain them, and to consider and answer all the Objections (many whereof I foresee) that may be alleged against it; and because I know a more likely hypothesis for gravity, which I can make out by experiment; I shall at present proceed to other Queries, contenting myself to have here only given a hint of what I may elsewhere determine.  
A Third Query than was, whether the heterogeneity of the ambient fluid may not be accounted a secondary cause of the roundness or globular form of the greater bodies of the world, such as are those of the Sun, Stars and Planets, the substance of each of which seems altogether heterogeneous to the circum-ambient fluid aether?  
A Fourth was; Whether the globular Form of the smaller parcels of matter here upon the Earth, as that of Fruits Pebbles or F●ints &c. (which seem to have been a Liquor at first) may not be caused by the heterogeneous ambient fluid. For thus we see that melted Glass will be naturally formed into a round Figure; so likewise any small Parcel of any fusible body, if it be perfectly enclosed by the Air, will be driven into a globular Form, and when cold, will be found a solid Ball. This is plainly enough manifested to us by their way of making shot with the drops of Lead, or a shower of Rain congealed in its falling into Hailstones; and if you gently let fall a drop of water upon small sand or dust, you shall find as 'twere an artificial round stone quickly generated. I cannot upon this occasion omit the mentioning of the strange kind of Grain which I have observed in a stone brought from Kettering in Northamptonshire, and therefore called by Mason's Kettering-Stone, like to which are found also at Tormanton, near to Sudberry in Glocestershire: For I found it to consist of a great number of small and almost globular parcels of matter, which to my naked eye looked much like the Cob or Spawn of a Herring, though through a Microscope it looked like a great Beach of round Pibble stone, such as I have often seen by the Seashore, some of which I perceived to be hollow, much like the broken Shells of Granades: Which brings into my mind what I long since observed in the fiery Sparks that are struck out of a flint, etc. For having a great desire to see what was left behind, after the Spark was gone out, I purposely struck fire over a very white piece of Paper, and observing diligently where some conspicuous sparks went out, I found a very little black spot no bigger than the point of a Pin, which through a Microscope appeared to be a perfectly round Ball, looking much like a polished ball of Steel, insomuch that I was able to see the Image of the window reflected from it, making the like Observation in very many others, I found some to be hollow, and to look like the broken shells of Grandees, much like that represented in the 4th. Figure. I cannot here stay to examine the particular Reasons of it, but shall only hint, that I imagine it to be some small parcel of the flint or steel (for I find it may be of either) which by the violence of the motion of the stroke (most of which seems to be impressed upon those small parcels) is made so glowing hot, that 'tis melted into a Vitrum, which by the ambient Air is driven into a round Globul.  
A Fifth thing which I thought worth Examination was, Whether the motion of all kind of Springs, might not be reduced to the Principle whereby the included heterogeneous fluid seems to be moved; or to that whereby two solids, as Marbles, or the like, are thrust and kept together by the Ambient fluid.  
A Sixth thing was, Whether the Rising and Ebullition of the water out of Springs & Fountains (which lie much higher from the Centre of the earth than the superficies of the Sea, from whence it seems to be derived) may not be explicated by the Rising of water in a smaller Pipe: For the Sea-water being as it were strained through the Pores or Crevices of the earth, is as it were included in little Pipes, where the pressure of the Air has not so great a power to resist its Rising: But examining this way, and finding in it several difficulties almost irremoveable, I thought upon a way that would much more naturally and conceiveably explain it, which was by this following Experiment: I took a Glass Tube of the form of that described in the 6th. Figure, and choosing two heterogeneous fluids, such as water and Oil, I poured in as much water as filled up the Pipes as high as (A. B.) then putting in some Oil into the Tube (A. C.) I depressed the superficies (A.) of the water to (E.) and B. I raised to G. which was not so high perpendicularly as the superficies of the Oil F. by the space (F. 1) wherefore the proportion of the gravity of these two Liquors was as (G. H.) to (F. E.)  
This Experiment I tried with several other Liquors, and particularly with fresh water and salt (which we made by dissolving Salt in warm water) which two though they are nothing heterogeneous, yet before they would perfectly mix one with another, I made trial of the Experiment: Nay, letting the Tube wherein I tried the Experiment remain for many days, I observed them not to mix; but the superficies of the fresh was rather more than less elevated above that of the salt. Now the proportion of the gravity of Sea-water, to that of Riverwater, according to Stevinus and Varenius, (for I have not now the opportunity of making trial myself) is as 46. to 45. that is, 46. Ounces of the salt-water will take up no more Room than 45▪ of the fresh▪ Or reciprocally 45 pints of salt, water weigh as much as 46 of fresh. Though I conceive the difference to be much more, for I found the proportion of Brine to fresh water to be near 13 to 12: Supposing therefore G. H. M. to represent the Sea, and F. I. the height of the Mountain above the Superficies of the Sea, F. M. a Cavern in the Earth, beginning at the bottom of the Sea, and terminated at the top of the Mountain, L. M▪ the Sand at the bottom, through which the water is as it were strained, so as that the fresher parts are only permitted to transude, and the saline kept back; if therefore the proportion of G. M. to F. M. be as 45. to 46. then may the Cylinder of salt water G. M. make the Cylinder of fresh water to rise as high as E. and to run over at N. I cannot here stand to examine or confute their Opinion, who make the depth of the Sea below its Superficies, to be no more perpendicularly measured than the height of the Mountains above it: 'Tis enough for me to say, there is no one of those that have vented it, have experimentally known the perpendicular of either; nor shall I here determine, whether there may not be many other causes of the separation of the fresh water from the salt, as perhaps some parts of the earth through which it is to pass, may contain a salt, that mixing and uniting with the Sea salt, may precipitate it▪ much after the same manner as the Alkalizate and Acid Salts mix and precipitate each other in the preparation of Tartarum Vitriolatum. I know not also whether the exceeding cold (that must necessarily be) at the bottom of the water, may not help towards this separation, for we find, that warm water is able to dissolve and contain more salt, than the same cold; insomuch that Brines strongly impregnated by heat, if let cool, do suffer much of their salt to subside and crystallise about the bottom and sides. I know not also whether the exceeding pressure of the parts of the water one against another, may not keep the Salt from descending to the very bottom, as finding little or no room to insert itself between those parts, protruded so violently together, or else squeeze it upwards into the superior parts of the Sea, where it may more easily obtain room for itself, amongst the parts of the water, by reason that there is more heat and less pressure. To this Opinion I was somewhat the more induced by the relations I have met with in several Geographical Writers, of drawing fresh water from the bottom of the Sea, which is salt above. I cannot now stand to examine, whether this natural perpetual motion may not artificially be imitated: Nor can I stand to answer the Objections which may be made against this my Supposition: As,  
First, How it comes to pass, that there are sometimes salt Springs much higher than the Superficies of the water? And,  
Secondly, Why Springs do not run faster and flower, according to the varying height made of the Cylinder of Sea-water, by the ebbing and flowing of the Sea?  
As to the First, In short, I say, the fresh water may receive again a saline Tincture near the Superficies of the Earth, by passing through some salt Mines, or else many of the saline parts of the Sea may be kept back, though not all.  
And as to the Second, The same Spring may be fed and supplied by divers Caverns, coming from very far distant parts of the Sea, so as that it may in one place be high, in another low water; and so by that means the Spring may be equally supplied at all times. Or else the Cavern may be so strait and narrow, that the water not having so ready and free passage through it, cannot upon so short and quick mutations of pressure, be able to produce any sensible effect at such a distance. Besides, that to confirm this hypothesis, there are many Examples found in Natural Historians, of Springs that do ebb and flow like the Sea: As particularly, those recorded by the Learned Camden, and after him by Speed, to be found in this Island: One of which, they relate to be on the Top of a Mountain, by the small Village. Kilken in Flintshire, Maris aemulus qui statis temporibus suas revomit & resorbet Aquas; which at certain times riseth and falleth after the manner of Sea-Tides. A Second in Caermardenshire, near Caermarden, at a place called Cantred Bichan; Qui (ut scribit Giraldus) naturali die bis undis deficiens, & toties exuberans, marinas imitatur instabilitates. That twice in four and twenty hours ebbing and flowing, resembleth the vustable Motions of the Sea. The Phanomena of which two may be easily made out, by supposing their Cavern by which they are fed, to arise from the bottom of the next Sea. A Third, is a Well upon the River Ogmore, in Glamorganshire, and near unto Newton, of which Camhden relates himself to be certified, by a Letter from a Learned Friend of his that observed it, Fons abest hinc, etc. The Letter is a little too long to be inserted, but the substance is this, that this Well ebbs and flows quite contrarily to the flowing and ebbing of the Sea in those parts: for 'tis almost empty at Full Sea, but full at Low water. This may happen from the Channel by which it is supplied, which may come from the bottom of a Sea very remote from those parts, and where the Tides are much differing from those of the approximate shores. A Fourth lies in Westmoreland, near the River Loder; Qui instar Euripi saepius in die reciprocantibus undis fluit & refluit, which ebbs and flows many times a day. This may proceed from its being supplied from many Channels, coming from several parts of the Sea, lying sufficiently distant asunder to have the times of High-Water differing enough one from the other; so as that whensoever it shall be High Water over any of those places where these Channels begin, it shall likewise be so in the Well. But this is but a Supposition.  
A Seventh thing was, Whether in general the Glutinousness of most bodies may not be partly attributed to this property! For supposing glutinous bodies to be such as will easily conform themselves to the superficies of homogeneal bodies, and being suffered for some time to rest in that Position, until they grow hard, the intercourse of the Air or other fluid body being hindered, the force requisite to disjoin those two superficies must necessarily be such as is able to preponderate and prevail against the pressure of the Air upon a superficies equal to that of the body which is touched by the glutinous substance; for these two touch so exactly, that 'tis impossible for the Air to get between, until they are somewhat disjoined, by which means the pressure of the Air can only be against the two outward sides opposite to those which join them together: This may be confirmed by the Experiment of two flat Marbles, pieces of Glass, and the like smooth bodies; for if they be so exactly plain, that by rubbing them together, you can detrude the interjacent Air, 
Of this much has been ●●id in the 31 〈◊〉 32 Experiments of the abovementioned Discourse ●f the Air, & 〈◊〉 more copiously explained in a Treatise of ●he same Honourable Author now in ●he Press.  you shall find them stick so hard, that an ordinary strength can hardly separate them; especially if they be of any bigness.  
This Property I say, may at least be the cause why some bodies adhere to Glass, and the like: For I am not ignorant, that as for Wood, and many other porous bodies, the glutinous substance may penetrate into their little cavities, and so hardening, become little Hooks or Buttons, that may contribute much to the former Cohesion.  
An Eighth Query was, Whether the dissolution or mixing of several bodies, whether fluid or solid, with saline or other Liquors, might not partly be attributed to this Principle of the congruity of those bodies and their dissolvents? As of Salt in water, Metals in several Menstruums, Unctuous Gums in Oils, the Mixing of Wine and water, etc. And whether precipitation be not partly made from the same Principle of Incongruity? I say partly, because there are in some dissolutions, some other Causes concurrent.  
I shall lastly make a much more seemingly strange and unlikely Query; and that is, Whether this Principle well examined and explained, may not be found a co-efficient in the most considerable Operations of Nature? As in those of Heat and Light, and consequently, of Rarefaction and Condensation, Hardness or Solidity and Fluidness, Perspicuity and Opacousness, Refractions and Colours, etc. Nay, I know not whether there may be many things done in Nature, in which this may not (be said to) have a Finger? This I may possibly further inquire into and examine, if God grant me Life and Opportunity. In the mean time, I would not be thought guilty of that Error, which the thrice Noble and Learned Verulam justly takes notice of, as such, and calls Philosophiae Genus Empiricum, quod in paucorum Experimentorum Angustiis & Obscuritate fundatum est. For I neither conclude from one single Experiment, nor are the Experiments I make use of, all made upon one Subject: Nor wrest I any Experiment to make it quadrare with any preconceived Notion. But on the contrary, I endeavour to be conversant in all kind of Experiments, and all and every one of those Trials, I make the standards (as I may say) or Touchstones by which I try all my former Notions, whether they hold not in weight and measure and touch, etc. For as that Body is no other than a Counterfeit Gold, which wants any one of the Proprieties of Gold, (such as are the Malleableness, Weight, Colour, Fixtness in the Fire▪ Indissolubleness in Aquafortis, and the like.) though it has all the other; so will all those notions be found to be false and deceitful, that will not undergo all the Trials and Tests made of them by Experiments. And therefore such as will not come up to the desired Apex of Perfection, I rather wholly reject and take a new, than by piecing and patching endeavour to retain the old, as knowing old things to be rather made worse by mending, than better. And this course I learned from Nature; whom we find neglectful of the old Body, and suffering its Decays and Infirmities to remain without repair, and altogether solicitous and careful of perpetuating the Species by new Individuals. And 'tis certainly the most likely way to erect a glorious and everlasting structure and Temple to Nature, such as she will be found (by any zealous Votary) to reside in; first to raze the old Pile built upon unstable Fancies and unsound opinions, and to begin a new upon a sure Foundation of Experiments. Thus Medea when she renewed old Aeson, first searches Heaven and Earth, gathers and collects simples and Ingredients of all kinds, nor would these do any thing till well mixed, concocted and digested.  Omnia confudit, summisque immiscuit ima. 
Then we find her examine whether it will do what she expected.  
Ecce, vetus calido versatus stipes aheno  
Fit viridis primo, nec longo tempore frondes  
Induit, & subito gravidis oneratur Olivis.  
At quacunque cavo spumas ejecit aheno  
Ignis, & in terram guttas cecidere calentes:  
Vernat humus floresque & mollia pabula surgunt.  
And finding it to come up to what she desired, she than begins her great work.  
Quae simul ac vidit stricto Medaea recludit  
Ense senis jugulum: veteremque exire cruorem  
Passa, replet succis:  
After which, what succeeded, but a miraculous Renovation?  
— Barba, comaeque  
Canitie posita, nigrum rapuere colorem  
Pulsa fugit macies: Abeunt pallorque situsque  
Adjectoque cavae supplentur corpore rugae:  
Membraque luxuriant—  
The Application of it is obvious, and therefore (to digress no further from the consideration of the Phaenomena, more immediately explicable by this Experiment) we shall proceed to show, That,  
As to the rising of water in a Filtre, the reason of it will be manifest to him that does take notice that a Filtre is constituted of a great number of small long solid bodies, which lie so close together, that the Air in its getting in between them, doth lose of its pressure that it has against the fluid without them, by which means the water or liquor not finding so strong a resistance between them as is able to counter balance the pressure on its superficies without, is raised upward, till it meet with a pressure of the Air which is able to hinder it. And as to the Rising of Oil, melted Tallow, Spirit of Wine, etc. in the Weeck of a Candle or Lamp, it is evident, that it differs in nothing from the former, save only in this, that in a Filtre the Liquor descends and runs away by another part▪ and in the Weeck the Liquor is dispersed and carried away by the Flame (which what it is, and how it consumes bodies, I shall on some other occasion by many luciferous Experiments manifestly prove) something there is ascribable to the heat, for that it may rarify the more volatile and spirituous parts of those combustible Liquors, and so being made lighter than the Air, it may be protruded upwards by that more ponderous fluid body in the Form of Vapours. But this can be ascribed to the ascension of but a very little, and most likely of that only which ascends without the Weeck, as for the Rising of it in a Sponge, Bread, Cotton, etc. above the superficies of the subjacent Liquor; what has been said about the Filtre (if considered) will easily suggest a reason, considering that all these bodies are bound with small holes or pores.  
From this same Principle also (viz.) the unequal pressure of the Air against the unequal superficies of the water) proceeds the cause of the accession or incursion of any floating body against the sides of the containing Vessel, or the appropinquation of two floating bodies, as Bubbles, Corks, Sticks, Straws, etc. one towards another. As for instance, Take a Glass-jar, such as (A. B.) in the 7th. Figure, and filling it pretty near the top with water, throw into it a small round piece of Cork, as (C.) and plunge it all over in water, that it be wet, so as that the water may rise up by the sides of it, then placing it any where upon the superficies, about an inch, or one Inch and a quarter from any side, and you shall perceive it by degrees to make perpendicularly toward the nearest part of the side, and the nearer it approaches it, the faster to be moved; the reason of which Phaenomenon will be found no other than this, that the Air has a greater pressure against the middle of the superficies, than it has against those parts that approach nearer, and are contiguous to the sides. Now that the pressure is not so much, may (as I showed before in the explication of the 3d d Figure) be evinced from the rising of the water near the sides, higher than that in the middle: Hence the Ball having a stronger pressure against that side of it which respects the middle of the superficies, than against that which respects the approximate side, must necessarily move towards that part from whence it finds least resistance, and so be accelerated, as the resistance decreases. Hence the more the water is raised under that part of its way it is passing above the middle, the faster it is moved: And therefore you will find it to move faster in E. than in D. and in D. than in C. Neither could I find the floating substance to be moved at all, until it were placed upon some part of the Superficies that was sensibly elevated above the height of the middle part. Now that this may be the true cause, you may try with a blown Bladder, and an exactly ro●nd Ball upon a very smooth Table. For if the Ball be placed under a part of the Bladder which is upon one side of the middle of its pressure, & you press strongly against the Bladder, you shall find the Ball moved from the middle towards the sides. Having therefore shown the reason of the motion of any float towards the sides, the reason of the incursion of any two floating bodies will easily appear: For the rising of the water against the sides of either of them, is an Argument sufficient, to show the pressure of the Air to be there less, than it is further from it, where it is not so much elevated; and therefore the reason of the motion of the other toward it, will be the same as towards the side of the Glass; only here from the same reason, they are mutually moved toward each other, whereas the side of the Glass in the former remains fixed. If also you gently fill the Jar so full with water, that the water is protuberant above the sides, of the same piece of Cork that before did hasten towards the sides, does now fly from it as fast towards the middle of the Superficies; the reason of which will be found no other than this, that the pressure of the Air is stronger against the sides of the superficies G. and H. then against the middle I. which may be argued from its being much lower than the middle; and therefore the consecution will be the same as in the former. It is very odd to one that considers not the reason of it, to see two bodies of wood to approach each other, as though they were endued with some magnetical vigour; which brings into my mind what I formerly tried with a piece of Cork or such like body, which I so ordered, that by putting a little stick into the same water, one part of the said Cork would approach and make toward the stick, whereas another would discede and fly away, nay it would have a kind of verticity, so as that if the aequator (as I may so speak) of the Cork were placed towards the stick, if let alone, it would instantly turn its appropriate pole toward it, and then run a tilt at it, and this was only by taking a dry Cork, and wetting one side of it with one small stroke; for by this means gently putting it upon the water, it would depress the superficies on every side of it that was dry, and therefore the greatest pressure of the Air being near those sides caused it either to chase away, or else to fly off from any other floating body, whereas that side only against which the water ascended, was thereby able to attract. I cannot here stay to explain the Reasons of magnetical and electrical attraction, nor the Reasons of gravity or magnetical direction and variation, they being little or nothing at all to my present Subject, and besides, will afford matter enough to fill another sheet when I have leisure.  
It remains only, that I should determine now high the water or other Liquor may by this means be raised in a smaller Pipe above the superficies of that without it: But to determine this, will be exceeding difficult, unless I could certainly know how much of the Air's pressure is taken off▪ by the smallness of such and such a Pipe, and whether it may be wholly taken off, that is, whether there can be a hole or poor so small, into which Air could not at all enter, though water might with its whole force, for were there such, 'tis manifest, that the water might rise in it to some five or six and thirty English Foot high. I know not whether there may not be such natural Pipes in the bodies of small Trees, which we usually call their Pores, But I have already pretergressed the bounds of a Sheet, which I at first prescribed myself for the explication of this Phaenomenon, and therefore I shall at present make  
AN END.