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 coefficient in the most considerable Operations of Nature? As in those of Heat, and Light, and consequently of Rarefaction and Condensation, Hardness, and Fluidness, Perspicuity and Opacousness, Refractions and Colours. &c. 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 have in some other passages of this Treatise further enquired into and shewn, that as well Light as Heat may be caused by corrosion, which is applicable to congruity, and consequently all the rest will be but subsequents: In the mean time I would not willingly be guilty of that Error, which the thrice Noble and Learned Verulam justly takes notice of, as such, and calls Philosophiæ 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 preconceiv’d Notion. But on the contrary, I endeavour to be conversant in divers kinds of Experiments, and all and every one of those Trials, I make the Standards or Touchstones, by which I try all my former Notions, whether they hold out in weight, and measure, and touch, &c. For as that Body is no other then 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 Aqua fortis, 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 new, then by piecing and patching, endeavour to retain the old, as knowing such things at best to be but lame and imperfect. And this course I learned from Nature; whom we find neglectful of the old Body, and suffering its Decaies and Infirmities to remain without repair, and altogether sollicitous and careful of perpetuating the Species by new Individuals. And it is certainly the most likely way to erect a glorious Structure and Temple to Nature, such as she will be found (by any zealous Votary) to reside in; to begin to build a new upon a sure Foundation of Experiments.
But to digress no further from the consideration of the Phænomena, more immediately explicable by this Experiment, we shall proceed to shew, 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-ballance 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 Oyl, melted Tallow, Spirit of Wine, &c. in the Week 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 Week the Liquor is dispersed and carried away by the Flame; something there is ascribable to the Heat, for that it may rarifie the more volatil and spirituous parts of those combustible Liquors, and so being made lighter then 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 Week. As for the Rising of it in a Spunge, Bread, Cotton, &c. 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 abound 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, &c. one towards another. As for instance, Take a Glass jar, such as AB in the seventh 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, the faster to be moved, the reason of which Phænomenon will be found no other then this, that the Air has a greater pressure against the middle of the superficies, then it has against those parts that approach nearer, and are contiguous to the sides. Now that the pressure is greater, may (as I shewed before in the explication of the third Figure) be evinced from the flatting of the water in the middle, which arises from the gravity of the under fluid: for since, as I shewed before, if there were no gravity in the under fluid, or that it were equal to that of the upper, the terminating Surface would be Spherical, and since it is the additional pressure of the gravity of water that makes it so flat, it follows, that the pressure upon the middle must be greater then towards the sides. Hence the Ball having a stronger pressure against that side of it which respects the middle of the superficies, then 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 decrease. 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 then in D, and in D then 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 round Ball upon a very smooth side of some pliable body, as Horn or Quicksilver. For if the Ball be placed under a part of the Bladder which is upon one side of the middle of its pressure, and you press strongly against the Bladder, you shall find the Ball moved from the middle towards the sides.
Having therefore shewn 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 shew the pressure of the Air to be there less, then 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 fixt. If also you gently fill the Jar so full with water, that the water is protuberant above the sides, 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 then this, that the pressure of the Air is stronger against the sides of the Superficies G and H, then against the middle I; for since, as I shewed before, the Principle of congruity would make the terminating Surface Spherical, and that the flatting of the Surface in the middle is from the abatement of the waters pressure outwards, by the contrary indeavour of its gravity; it follows that the pressure in the middle must be less then on the sides; 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 floating bodies of wood to approach each other, as though they were indued 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 Æquator (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 done only by taking a dry Cork, and wetting one side of it with one small stroak; 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.
It remains only, that I should determine how high the Water or other Liquor may by this means be raised in a smaller Pipe above the Superficies of that without it, and at what height it may be sustained: But to determine this, will be exceeding difficult, unless I could certainly know how much of the Airs pressure is taken off by the smalness of such and such a Pipe, and whether it may be wholly taken off, that is, whether there can be a hole or pore 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 the capillary Pipes in the bodies of small Trees, which we call their Microscopical pores, may not be such; and whether the congruity of the sides of the Pore may not yet draw the juyce even higher then the Air was able by its bare pressure to raise it: For, Congruity is a principle that not only unites and holds a body joyned to it, but, which is more, attracts and draws a body that is very near it, and holds it above its usual height.
And this is obvious even in a drop of water suspended under any Similar or Congruous body: For, besides the ambient pressure that helps to keep it sustein’d, there is the Congruity of the bodies that are contiguous. This is yet more evident in Tenacious and Glutinous bodies; such as Gummous Liquors, Syrups, Pitch, and Rosin melted, &c. Tar, Turpentine, Balsom, Birdlime, &c. for there it is evident, that the Parts of the tenacious body, as I may so call it, do stick and adhere so closely together, that though drawn out into long and very slender Cylinders, yet they will not easily relinquish one another; and this, though the bodies be aliquatenus fluid, and in motion by one another, which, to such as consider a fluid body only as its parts are in a confused irregular motion, without taking in also the congruity of the parts one among another, and incongruity to some other bodies, does appear not a little strange. So that besides the incongruity of the ambient fluid to it, we are to consider also the congruity of the parts of the contein’d fluid one with another.
And this Congruity (that I may here a little further explain it) is both a Tenacious and an Attractive power; for the Congruity, in the Vibrative motions, may be the cause of all kind of attraction, not only Electrical, but Magnetical also, and therefore it may be also of Tenacity and Glutinousness. For, from a perfect congruity of the motions of two distant bodies, the intermediate fluid particles are separated and droven away from between them, and thereby those congruous bodies are, by the incompassing mediums, compell’d and forced neerer together; wherefore that attractiveness must needs be stronger, when, by an immediate contact, they are forc’d to be exactly the same: As I shew more at large in my Theory of the Magnet. And this hints to me the reason of the suspension of the Mercury many inches, nay many feet, above the usual station of 30 inches. For the parts of Quick-Silver, being so very similar and congruous to each other, if once united, will not easily suffer a divulsion: And the parts of water, that were any wayes heterogeneous, being by exantlation or rarefaction exhausted, the remaining parts being also very similar, will not easily part neither. And the parts of the Glass being solid, are more difficultly disjoyn’d; and the water, being somewhat similar to both, is, as it were, a medium to unite both the Glass and the Mercury together. So that all three being united, and not very dissimilar, by means of this contact, if care be taken that the Tube in erecting be not shogged, the Quicksilver will remain suspended, notwithstanding its contrary indeavour of Gravity, a great height above its ordinary Station; but if this immediate Contact be removed, either by a meer separation of them one from another by the force of a shog, whereby the other becomes imbodied between them, and licks up from the surface some agil parts, and so hurling them makes them air, or else by some small heterogeneous agil part of the Water, or Air, or Quicksilver, which appears like a bubble, and by its jumbling to and fro there is made way for the heterogeneous Æther to obtrude it self between the Glass and either of the other Fluids, the Gravity of Mercury precipitates it downward with very great violence; and if the Vessel that holds the restagnating Mercury be convenient, the Mercury will for a time vibrate to and fro with very large reciprocations, and at last will remain kept up by the pressure of the external Air at the height of neer thirty inches. And whereas it may be objected, that it cannot be, that the meer imbodying of the Æther between these bodies can be the cause, since the Æther having a free passage alwayes, both through the Pores of the Glass, and through those of the Fluids, there is no reason why it should not make a separation at all times whilst it remains suspended, as when it is violently disjoyned by a shog. To this I answer, That though the Æther passes between the Particles, that is, through the Pores of bodies, so as that any chasm or separation being made, it has infinite passages to admit its entry into it, yet such is the tenacity or attractive virtue of Congruity, that till it be overcome by the meer strength of Gravity, or by a shog assisting that Conatus of Gravity, or by an agil Particle, that is like a leaver agitated by the Æther; and thereby the parts of the congruous substances are separated so far asunder, that the strength of congruity is so far weakened, as not to be able to reunite them, the parts to be taken hold of being removed out of the attractive Sphere, as I may so speak, of the congruity; such, I say, is the tenacity of congruity, that it retains and holds the almost contiguous Particles of the Fluid, and suffers them not to be separated, till by meer force that attractive or retentive faculty be overcome: But the separation being once made beyond the Sphere of the attractive activity of congruity, that virtue becomes of no effect at all, but the Mercury freely falls downwards till it meet with a resistance from the pressure of the ambient Air, able to resist its gravity, and keep it forced up in the Pipe to the height of about thirty inches.
Thus have I gently raised a Steel pendulum by a Loadstone to a great Angle, till by the shaking of my hand I have chanced to make a separation between them, which is no sooner made, but as if the Loadstone had retained no attractive virtue, the Pendulum moves freely from it towards the other side. So vast a difference is there between the attractive virtue of the Magnet when it acts upon a contiguous and upon a disjoyned body: and much more must there be between the attractive virtues of congruity upon a contiguous and disjoyned body; and in truth the attractive virtue is so little upon a body disjoyned, that though I have with a Microscope observed very diligently, whether there were any extraordinary protuberance on the side of a drop of water that was exceeding neer to the end of a green stick, but did not touch it, I could not perceive the least; though I found, that as soon as ever it toucht it the whole drop would presently unite it self with it; so that it seems an absolute contact is requisite to the exercising of the tenacious faculty of congruity.