by the agitation of a mans body that sometimes abundance of Air is seen to ascend up thorow the Pipe which in effect makes the Cylinder shorter than it ought to be But if so be the end of the Pipe be immerged among Quick-silver contained in a Glass with a narrow orifice so that it may be stopped compleatly you will find no reciprocations at all And to make all things the more sure the Glass may be filled up either with Mercury or with Water above the Mercury by which means the Cylinder in the down-coming or in the up-going shall remain immoveable Besides the stopping of the orifice of the said Glass you may have a wider Vessel that may receive the same Glass into it and it being full of Water may so cover the sealed orifice that there shall be no hazard of any Air coming in Or this Experiment may be first tried at the root of the Hill and having stopped compleatly the mouth of the Vessel the whole Engine may be carried up to the top where you will find the Mercury subside and fall down so much namely after the said orifice is opened for as the stopping of the orifice at the root of the Hill is the cause why that same degree of Pressure remains in the stagnant Liquor so the opening of it upon the top of the Hill is the cause why it becomes less This Experiment lets us see that the Pressure of the Air seems to be as the Pressure of the Water namely the further down the greater and the further up the less and therefore as by coming up to the top of the Water there is no more Pressure so by coming up to the top of the Air there is no more weight in it which in effect sayes that the Air hath a determinat hight as the Water hath From this Experiment we cannot learn the determinat hight of the Air because the definit hight of the Mountain is not known I know there are some who think that the Air is indefinitly extended as if forsooth the Firmament of fixed Stars were the limits of it but I suppose it is hard to make it out OBSERVATION V. JUne 5. 1670. I observed the Sun within 3 minuts of setting to have a perfect oval figure the two ends lying level with the Horizon His colour was not red as ordinarily but bright and clear as if he had been in the Meridian neither was the Sky red but clear also And by the help of the Pendulum Clock I have observed his body to be longer in setting than it ought by eight minuts and sometimes by ten and his Diameter longer in going out of sight than it ought by two and sometimes by three minuts The reason of these Phenomena must be the Refraction unquestionably OBSERVATION VI. UPon Saturday evening the 30 of Iuly 1670 and the night following till about two a Clock in the Sabbath morning there fell out a considerable rain with great thunder and many lightnings About Sun-set the convocation of black clouds appeared first towards the Horizon in the South-west with several lightnings and the wind blowing from that point carried the clouds and rain over Mid and East-Lothian towards the Firth and Sea-coast About 9 a clock the whole Heavens almost were covered with dark clouds yet the rain was not very great neither were the thunder claps frequent but every fifth or sixth second of time a large and great lightning brake out But before the thunder crack was heard which happened every fourth or fifth minut the lightning was so terrible for greatness and brightness that it might have bred astonishment And because the night was very dark and the lightning very splendid a man might have perceived houses and coâ—n-fields at a great distance And if any had resolved to catch it in the breaking out it did so dazle the eyes that for half a minut he was not able to see any thing about him Sometimes the lightning that went before the thunder brake forth from the clouds like a long spout of fire or rather like a long flame raised high with a Smiths Bellows but did not continue long in sight Such an one above the Firth was seen to spout downward upon the Sea Sometimes there appeared from the one end of the cloud to the other an hiatus or wide opening all full of fire in form of a long furrow or branch of a River not straight but crooked I suppose the breadth of it in it self would have been twenty pace and more and the length of it five or six hundred pace the duration of it would have been about a second of time Sometimes a man might have perceived the nether side of the cloud before the crack came all speckled with streams of fire here and there like the side of an Hill where Moor-burn is which brake forth into a lightning But there was one after which followed a terrible thunder crack which far exceeded all the rest for quantity and splendor It brake out from the cloud being shot from North to South in form of fire from a great Cannon but in so great quantity as if a Gun ten foot wide with 500 pound weight of Powder in it had been fired And surely the lightning behoved to be far greater in it self seeing it appeared so great at so great a distance It did not evanish in an instant like the fire of a Gun but continued about a second and an half by reason it seems that it could not break out all at once This did so dazle the sight that for half a minut almost nothing was seen but like a white mist flying before the eyes The whole Countrey about was seen distinctly All these great lightnings were seen a considerable time before the crack was heard Sometimes 30 seconds numbered by the Pendulum Clock interveened namely when the thunder was at a distance about 7 or 8 miles Sometimes 15 or 16 only interveened But when the thunder was just above our head no moe passed than 7 or 8 which seems to demonstrat that these thick black clouds out of which the thunder breaks are not a Scottish mile from the earth when they are directly above us 'T is observable that in all lightnings and thunderings there is no smoke to be seen which seems to evince that the matter whereof they are generated must be most pure and subtil Who knows but this Countrey that abounds with Coal may occasion more thunder and lightnings than other places namely by sending up sulphurious exhalations to the middle region of the Air wherewith the Coal-mines abound OBSERVATION VII THis is a method for finding out the true South and North Points which are in effect very difficult to know Take therefore four pieces of Timber each one of them five foot long and about six inches thick square-wise Sharpen their ends and fix them so in the ground that they may stand Perpendicular and as near to South and North by a Magnetick Needle
Pressure from the ambient Air. OBSERVATION XI TAke a slender chord about 4 or 5 yards in length and fasten the middle of it to the seiling of a Room with a nail so that the two ends of it may hang down equally Take next a piece of Wood two or three foot long two inches broad and one inch thick and boring an hole in each end of it put through the two ends of the chord and fasten them with knots but so that the piece of Wood may ly Horizontal and be in a manner a Pendulum to swing from the one end of the Chamber to the other Take next a Bullet of Lead or Iron about 20 or 24 ounces and lay it upon the said piece of Wood but because it cannot well ly without falling off therefore nail upon the ends and the sides of the Timber four pieces of Sticks on each end one and on each side one as Ledgets for keeping the Bullet from falling off All things being thus ordered draw up the piece of Wood towards the one side of the Room by which means losing its horizontal position it will ly declining-wise like the roof of an house In this position lay the Iron Bullet in the upmost end of it and then let them both pass from your fingers the one end of the Wood going foremost and you will find it swing towards the other side of the house and return again as a Pendulum This motion if the Wood be well guided in its vibrations will last perpetually because in its moving down the Bullet is hurled from the one end of the Wood to the other and hits it so smartly that it begets in it an impulse whereby it is carried farder up than it would be without it By this means the vibrations get not liberty to diminish but all of them are kept of the same length In the second vibration the same Bullet is hurled back again to the other end and hiting it with all its weight creats a second impulse wherewith the Wood is carried as far up as the point it was first demitted from Though this may seem a pretty device to please the fancy that 's many times deceived while things are presented to it by way of speculation yet upon tryal and experience there will be found an unspeakeable difficulty and it 's such an one that a man would not readily think upon I said that when the Wood was let go and was in passing down the Bullet in it would hurl down and hit the oppsite end and beget an impulse but there is no such thing for verily though the Bullet be laid upon a very declining plain Board whereupon no man could imagine a round body could ly yet all the time the Board is in swinging from the one side of the Chamber to the other and consequently sometimes under an horizontal and somtimes under an declining position the Bullet lies dead in the place where you first placed it This Observation is not so much for a perpetual motion as for finding out the reason of this pretty Phenomenon namely what 's the cause why the Bullet that cannot ly upon a reclining Board while it 's without motion shall now ly upon it while it 's under motion What is more difficult and nice to ly upon any thing that declines from a levell than Quick-silver yet lay never so much of it upon this Board while it is swinging it shall ly dead and without motion But no sooner you stop the motion of the wood but assoon the Bullet or the Quick-silver is hurled either this way or that way OBSERVATON XII I Find it mentioned by some learned persons that when a Ship is under Sail if a stone be demitted from the top of the Mast it will move down in a line parallel with it and fall at the root Some might think it ought not to fall directly above the place it hang over but rather some distance behind seing the Ship hath advanced so much bounds in the time wherein the stone is coming down Likewise while a Ship is under Sail let a man throw up a stone never so high and never so perpendicular as to his apprehension yet it will fall down directly upon his head again notwithstanding that the Ship hath run perhaps her own length in the time while the stone was ascending and descending This experiment I find to hold true which may be easily tryed especially when a man is carried in a Boat upon smooth Water drawn by a horse as is done in some places abroad Let him therefore throw up a little Stone or any heavy Body and he will find it descend just upon his head notwithstanding that the Horse that draggs the Boat be under a gallop and by this means hath advanced ten or twelve paces in the time Or while the Boat is thus running let a man throw a stone towards the brink of the VVater in this case he shall not hit the place he aimed at but some other place more forward This lets us see that when a Gun is fired in a Ship under Sail the Bullet cannot hit the place it was directed to Neither can a man riding with a full Career and shooting a Pistol hit the person he aims at but must surely miss him notwithstanding that though in the very instant of time wherein he fires the mouth of the Pistol was most justly directed For remedy whereof allowance must be granted in the aiming at the mark VVhile a man throws up a stone in a Ship under Sail it must receive two distinct impulses one from the hand whereby it is carried upward the other from the Ship whereby it is carried forward By this means the stone in going up and coming down cannot describe a perpendicular but a crooked Line either a Parabola or a Line very like unto it Neither can it describe a perpendicular Line in coming down from the top of the Mast though in appearance it seem to do so but a crooked one which in effect must be the half of that which it describes in going up and coming down For this same cause a stone thrown horizontally or towards the brink of the VVater must describe a crooked Line also And a Pistol Bullet shot while a man is riding at a full Carreer must describe a Line of the same kind Note that a man walking from the Stern of a Ship to the Head walks a longer way than in walking from the Head to the Stern Secondly a man may walk from the Head to the Stern and yet not change his place 'T is observable that a man under board will not perceive whether the Ship be sailing or not and cannot know when her Head goes about And it is strange that when a man is inclosed in a Hogs-head though he have light with him yet let him be never so oft whirled about he shall not know whether he be going about or not OBSERVATION XIII I Found in a Philosophical transaction lately Printed
80 in the fourth and so forth untill it become 1000 he will find the greater difficulty the longer he pulls 'T is just so with Air or Water raising Mercury in a Tub for as the Cylinder of the Mercury grows higher by rising so it becomes heavier and consequently the imaginary surface upon which the Base of the Pillar rests is more and more burdened and so becomes less and less able to press it up This leads us to a clear discovery of the reason why 't is more difficult by suction to pull up Mercury in a Pipe than to pull up Water and more hard to suck up ten foot of Water then to suck up five For trial of this which is soon done take a slender Glass-pipe 30 or 40 inches long open at both ends and drown the one end among Quick-silver and put your mouth to the other and having sucked you will find greater difficulty to pull up thorow the Pipe 15 inches of Mercury than to pull up 10 or 8 and far greater difficulty to suck up 20 than to pull up 15. It may be objected that if a man had strength sufficient in his Lungs to suck out the whole Air of the Pipe thirty inches of Mercury would come as easily up as three which seemes to prove that the difficulty of the Mercurie's up-coming depends not upon the weakness of the Air but upon the weakness of the Lungs and want of strength to suck I answer though a man were able to suck out the whole Air of the Pipe yet 30 inches will never ascend so easily as ten nor ten so easily as three and that for the reasons already given But why is it then say you that the stronger the suction be the higher the Mercury ascends in the Pipe I answer the suction serves for no use but to remove the impediment that hinders the Mercury from coming up which is nothing else but the Air within the Pipe Now the more of this Air that 's taken away by suction the stronger the suction is the more Air is taken away the â—arder up comes the Mercury But why ought there to be difficulty in the suction of Mercury to the altitude of 15 or 20 inches more than in the suction of Water to that altitude I answer when I suck Water up thorow a Pipe the suction of the Air above it is easie because the ascending Water helpes much to drive it up to the mouth the outward Air driving up both But the suction is difficult in Mercury because the ascending liquor does not help so much to drive up the Air to the mouth as the Water does And the reason is because the Air being more burdened with 15 inches of Mercury than with 15 inches of Water cannot so easily drive up the one as the oâ—her and so Mercury cannot so easily drive up the Air of the Pipe to the mouth as Water does In a word according to the difference of specifick weight between Water and Mercury so is the difficulty of suction therefore because Mercury is 14 times heavier than Water there is 14 times more difficulty to pull up the one than the other Note that suction is not taken here strictly as contradistinguished from pulsion but in a large sense as it may comprehend it To proceed a little further let us suppose the Pillar of Mercury see the 11. Figure G H that 's raised by the surface of Air F G to be 29 inches and every inch to weigh one ounce Secondly that the said surface has 29 degrees of power or force in it for in all counterpoises the Pondus and the Potentia are equal therefore if the Mercury be 29 inches the Potentia of the surface must have 29 degrees of strength or force in it to counterballance the Pondus These things being supposed which are evident let us imagine the surface of Air to raise the Mercury one inch above F G. In this case the surface is weaker than it was which I prove evidently because it is now but able to raise 28 of Mercury Imagine next the said surface to have raised the Mercury two inches above F G then it follows that it must be yet weaker because it 's now but able to raise 27 inches for by supporting two ounce of the Pondus it loseth two degrees of it's own Potentia In raiâ—ing three inches of Mercury it is three degrees weaker and in raising four it is four degrees weaker and so forth therefore having raised 28 inches there is but one degree of force remaining in the surface And when it hath raised the whole namely 29 it is no more able and can no more press For confirmation put the case that the surface of Air F G were as able and had as much Pressure in it after it hath raised 29 inches of Mercury as it is after the raising of 10 then it follows of necessity that after the raising of 20 it shall raise 19 moe which is impossible seing the greatest altitude is 29. It follows of necessity I say because after the raising of 10 it is able to raise 19 moe therefore if it be as able after 20 as after 10 it must raise 19 after 20. Yea if it be as able after 20 as 10 it must be as able after 29 as 10. If this be then it may raise other 29 and a third 29 and so in infinitum Therefore I conclude that when two Fluid Bodies are in equilibrio one with another or when the pondus is equal to the potentia none of them doth actually press upon another at least the surface hath lost all its Power and Pressure which is also evident in the Pillar For understanding this let us suppose A C B Figure 11. to be a Pipe 58 inches long and full of Mercury and every inch of it to weigh one ounce Now when the orifice D is opened there is here as great an inequality between the pondus and the potentia of the surface of Air E B on which it rests as was between the surface F G and the pondus of Mercury H G. For as F G had 29 degrees of power to raise G H so the Pillar A B has 29 ounce of weight to overcome the surface E B. And as the surface F G became one degree weaker by raising one inch of the Mercury H G and two degrees weaker by raising two inches and so forward till it lost all its Pressure so the Pillar by falling down one inch loseth one ounce of the weight by falling down two it loseth two ounce and so forward till by falling down from A to C it loseth all its Weight and Pressure But here occurreth a difficulty for if the surface F G hath lost all its Pressure by raising the Mercury from G to H and if the Pillar C B hath lost all its Pressure by falling down from A to C it follows that when a Pillar of a Fluid and a surface of a Fluid are in equal termes or brought to
pillars higher without any alteration at least considerable in the weight for it still remains a foot of water whatever be the hight of the pillars above it Lastly the weight of a Fluid is essential to it but the Pressure is only accidental because it is only generated and begotten in the inferiour parts by the weight of the superiour which weight may be taken away THEOREM XXIII Though the Bensil of a Fluid be not the same thing formally with the weight yet are they the same effectively THis proposition is true in order to many other things besides Fluids for we see that the Sun and Fire are formally different yet they may be the same effectively because the same effects that are done by the heat of the Sun may be done by the heat of the Fire So the same effects that are produced by the weight of a Fluid may be done by the Pressure and Bensill of it Thus the Mercurial Cylinder in the Torricellian Experiment may be either sustained by the Bensil of the Air or the weight of it By the Bensil as when no more Air is admitted to rest upon the stagnant Mercury then three or four inches the rest being secluded by stopping the orifice of the Vessel By the weight of it as when an intire Pillar of Air from the top of the Atmosphere rests upon the face of the stagnant Quicksilver It is also evident in a Clock which may be made to move either by a weight of Lead or by the force and power of a Steel Spring THEOREM XXIV The surfaces of Waters are able to sustain any weight whatsoever provided that weight press equally and uniformly Figure 1. THis is evident because the imaginary surface of VVater O T V X doth really support the whole sixteen Cubes of VVater above it yea though they were sixteen thousand And the reason is because they press most equally and uniformly VVhat I affirm of the imaginary surface the same I affirm of the first and visible For let a plain body of lead never so heavy be laid upon the top of the VVater A B C D yet will it support it and keep it from sinking provided it press uniformly all the parts of that surface It is clear also from the subsequent Theorem THEOREM XXV The surfaces of all Waters whatsoever support as much weight from the Air as if they had the weight of thirty four foot of Water above them or twenty nine inches of Quick-silver pressing them THis Proposition is evident from this that the Pressure of the Air is able to raise above the surface of any Water a Pillar of Water thirty four foot high For put the case there were a Pump fourty foot high erected among stagnant Water and a Sucker in it for extracting the internal Air a man will find that the Water will climb up in it four and thirty foot which Phenomenon could never happen unless the surface of the stagnant Water among which the end of the Pump is drowned were as much prest with the Air as if it had a burden of Water upon it thirty four foot high The second part is also evident because if a man drown the end of a long Pipe in a Vessel with stagnant Quick-silver and remove the Air that 's within the Pipe by a Sucker or more easily by the help of the Air-pump he will find the Liquor to rise twenty nine inches above the surface below which thing could never come to pass unless the Pressure of the Air upon the surfaces of all Bodies were equivalent to the Pressure and weight of twenty nine inches of Quick-silver THEOREM XXVI All Fluid Bodies have a sphere of Activity to which they are able to press up themselves or another Fluid and no further which is less or more according to the altitude of the pressing Fluid Figure 2. FOr understanding this Proposition let us imagine G H C D to be a Vessel in whose bottom there are five inches of Mercury E F C D. Next that above the stagnant Mercury there are thirty four foot of Water resting namely A B E F. Lastly that upon the surface of the said Water there is resting the Element of Air G H A B whose top G H I reckon to be about six thousand fathom above A B. Besides these let us imagine that there are here three Pipes open at both ends the first whereof C A G having it 's lower orifice C drowned among the stagnant Mercury E F C D goeth so high that theu pper orifice goeth above the top of the Air G H. The second whose lower orifice I is only drowned among the Water A B E F reaches to the top of the Air likewise The third whose open end K is above the surface of the VVater A N B and hanging in the open Air goeth likewise above the Atmosphere These things being supposed we see that no Fluid can by its own proper weight press any part of it self higher then it 's own surface seing the stagnant Mercury E F C D cannot press it self within the Pipe C G higher then E. Neither can the VVater A B E F press it self higher within the Pipe I L then the point N. Lastly neither can the Air G H A B press it self within the Pipe K M higher then M. But when one Fluid presseth upon another as the VVater A B E F upon the Mercury E F C D then doth the said Mercury ascend higher than it 's own surface namely from E to O which point is the highest to which the thirty four foot of VVater A B E F can raise the Mercury which altitude is twenty nine inches above the surface E I F. But if a second Fluid be superadded as the whole Air G H A B then must the Mercury according to that new Pressure rise by proportion so rises the Mercury from O to P other twenty nine inches By this same additional weight of Air the Water rises thirty four foot in the Pipe I L namely from N to R. Now I say the outmost and highest point to which the Element of Air G H A B can raise the Mercury is from O to P for by the Pressure of the Water A B E F it rises from E to O. And the highest point to which the said Air can raise the VVater is from N to R. The reasons of these determinate altitudes must be sought for from the altitudes of the incumbing and pressing Fluids for as these are less or more so is the altitude of the Mercury and of the VVater within the Pipes more or less The hight therefore of the Mercury E O is twenty nine inches because the deepness of the pressing water A B E F is thirty four foot And the hight of the VVater N R is thirty four foot because the hight of the Air G H above A B is six thousand fathom or thereabout And for the same reason is the Mercury O P twenty nine inches THEOREM XXVII
M G H. The same Phenomenon happens in taking the Air out of the narrow Pipe F K. The reason is still unequal Pressure for in removing the Air that 's within the Pipe the part of the surface M and the part H remaines burthened while the part G is freed of its burden therefore this part of the surface being liberated of its burden that came down through the Pipe instantly rises and climbs up as far as the outward Air resting upon M and H can raise it which is to E 34 foot for the Pressure of the Air upon the surfaces of all Waters according to the 25 Theorem being equivalent to the weight of 34 foot of Water must raise the said Water in the Pipe 34 foot You do not wonder why it rises from I to G as in the first experiment no more ought you to wonder why it rises from G to E seing the weight of the Air doth the same thing that 34 foot of Water resting upon the surface M H would do From this experiment we see first that the Pressure of the Air is the proper cause of the motion of Water up thorow Pumps and Siphons or any other instrument that 's used in Water-works of that kind for if the weight of the Air resting upon the surface M H be the cause why the Water climbs up from G to E the same must be the cause why the stagnant Water followes the Sucker of the Pump while it 's pulled up And the same is the cause why Water ascends the Leg of a Siphon and is the cause why motion continues after suction is ended We see secondly that every Pressing Fluid hath a Sphere of activity to which it is able to raise the Fluid that is pressed This is evident in this experiment because the Pressure of the Air resting upon M H is able to raise the Water the hight of E in the wide Pipe and the hight of F in the narrow and no further even though the said Pipes were far longer and this altitude and highest point is precisely 34 foot between Air and Water We see thirdly that 't is all one matter whether Pumps and Siphons be wider or narrower whether the tub of the Baroscope be wherein the Mercury is suspended of a large Diameter or of a lesser Diameter This is also evident from the same experiment seing there is no more difficulty in causing the Water ascend the wide Pipe than in causing it ascend the narrow one And the reason is because the pressing Fluid repects not the pressed Fluid according to its thickness and breadth but only according to its altitude Therefore ' its as easie for the Air to press up Water through a Pump four foot in Diameter as to press it up through a Pump but one foot in Diameter EXPERIMENT IV. Figure 7. THis Schematism represents a large Vessel full of Water whose first and visible surface is D E H K. The second that 's imaginary is L I six foot below it The third of the same kind is M G six foot lower The fourth is N F O six foot yet lower The last and lowest is A B C. There are here also four Tubs or rather one Tub under four divers positions with both ends open After this Tub D A is thrust below the Water till it ascend as high as D in it lift it up between your fingers till it have the position of the second Pipe E F and then you shall see as the orifice of the Pipe ascends the Cylinder of Water fall out by little and little until it be no longer than E F. Again lift it further up till it have the position of the Pipe H G then shall you find the Cylinder of Water become yet shorter Lastly if it be scituated as the Pipe K I the internal Water becomes no longer than K I. The reasons of these Phenomena are the same namely unequal Pressure for the Orifice A being lifted up as high as F it comes to the imaginary surface N O which is not under so much Pressure as the other is therefore one part of it being more burdened than another namely the part upon which the Cylinder of Water rests it presently yeelds and suffers the Cylinder to become shorter and lighter till it become no heavier then is proportionable to its own strength To make this reason more evident it is to be noted that no surface of Water is able to support a Cylinder higher then its own deepness that is to say if a surface be 40 foot deep it is able to sustain a Cylinder 40 foot high and no more therefore the surface N O being but 18 foot deep it cannot sustain a Cylinder 24 foot long for if that were then the Potentia should be inferiour to the Pondus which is impossible in the Hydrostaticks In effect it were no less absurdity then to say 18 ounces are able to counterballance 24. For a second trial lift up the same Pipe higher till it acquire the position of the Tub G H in this case the Cylinder of Water within it becomes yet shorter even no longer than G H. The reason is the same namely unequal Pressure for when a Cylinder of Water 18 foot high comes to rest upon this surface that is but 12 foot deep it makes one part of it more burdened then another therefore the part that is more prest presently yeelds and suffers the Cylinder to fall down till the Pondus of it become equal to its own Potentia For the last trial lift up the Tub till it acquire the position of the Pipe K I in this case the Water within it becomes no longer then K I the surface L I that is but six foot deep not being able to sustain a Cylinder 12 foot high From this Experiment we see first that in all Fluid Bodies there is a Pressure which is more or less according to the deepness of that Fluid this is evident from the four several surfaces there being more Pressure and force in the lowest A B C then in the next N O and more in this then in the surface M G and more in this then in L I. We see secondly that in all Fluids there is a Pondus and a Potentia which two are alwayes of equal force and strength the Potentia is clear and evident in the surface by supporting the Pillar which Pillar is nothing else but the Pondus supported And that they are alwayes of equal strength is most evident also for when you endeavour to make the Pondus unequal to the Potentia in making a surface 18 foot deep to support a Pillar 24 foot high they of their own accord become equal the Pillar becoming shorter and suitable to the strength of the surface that sustains it We see thirdly that 't is impossible for one part of the same Horizontal surface to be more burdened then another for when you endeavour to do it by setting a longer Pillar upon it the part burdened
instantly yeelds till it be no more prest then the next part to it We see fourthly that the inequality that is between the Pondus and the Potentia in Fluids is the proper cause of the motion of Fluids For when you endeavour to make a surface 30 foot deep sustain a Pillar 40 foot high this inequality is the true cause why the Pillar subsides and falls down and why the surface yeelds and gives way to it And this inequality is the true cause why the motion of Water thorow Siphons continues For understanding this you must conceive a Siphon to be nothing else but a crooked Pipe with two legs the one drowned among Water the other hanging in the open Air. The use of it is for conveying Wine or Water from one Vessel to another which is easily done by suction Now after suction is ended the motion of the Water continues till the surface become lower then the orifice out of which it runs The true reason then why the Water flows out is the inequality between the Potentia of the Air and the Pondus of the VVater the Pondus being stronger then the Potentia For in Air as in VVater we must conceive Horizontal surfaces and these surfaces to be endowed with Pressure and force as are the surfaces of VVater Now when the leg of a Siphon is hanging in the Air it must rest upon one surface or another and consequently the VVater in it must rest upon the same surface If the Potentia of the surface be stronger then the Pondus of the VVater the VVater is driven backward which alwayes comes to pass when the orifice is higher then the surface of the VVater of the Vessel among which the other leg is drowned If the Potentia of the surface of that Air be of equal power and strength with the Pondus of the VVater the VVater goeth neither backward nor forward but stands in equilibrio this happens when the orifice is neither higher nor lower than the surface of the VVater in the Vessel But if the Potentia of the surface of the Air be weaker than the Pondus of the VVater in this case the Air yeelds and suffers the VVater to run out even as a surface 30 foot deep yeelds to a Pillar of VVater 40 foot high The same inequality is the reason why VVater climbs up the Pump why VVater climbs up a Pipe when a man sucks with his mouth Before suction the Potentia that 's in the surface of VVater among which the end of the Pipe is drowned is of equal force with the Pondus of the Pillar of Air that comes down thorow the Pipe or Pump but assoon as a man begins to suck the said Pillar of Air becomes lighter and the VVater finding this presently ascends The same is the reason why the Mercury falls down to 29 inches in the Baroscope and no further for as long as the Pondus of the Pillar of Mercury exceeds the Potentia of the surface of Air so long doth the motion continue and when both are become equal in force the motion ceaseth VVhen the Glass-tub is 40 inches long and filled with Mercury and inverted after the common manner you are endeavouring as it were to cause a surface 29 inches deep sustain a Pillar 40 inches high which is utterly impossible in Fluids It is judged by many a wonder to see the deflux of the Mercury in the Baroscope but in effect there 's no more cause of admiration in it than to see the Cylinder of Water grow shorter by lifting the Pipe up from one surface to another From this Experiment we see the true reason why the Mercurial Cylinder of the Baroscope becomes shorter and shorter according as a man climbs up a mountain with it For at the root of the hill the surface of Air that sustains the Pillar of Mercury is of greater force than the surface at the middle part and this is stronger than any surface at the top The Pipe therefore being carried up from one surface to another the Mercury in it must subside and fall down even as the Water falls down and becomes shorter by lifting the Pipe from the surface A B C D to the surface N O. And as the whole VVater would fall down if the orifice I were lifted above the surface D E H K so if the Baroscope could be carried so high till it came above the top of the Air the whole Mercurial Cylinder would surely fall down And as by thrusting down the said Pipe to the bottom of the Vessel again as the Pipe D A the VVater ascends in it so by bringing down the Baroscope to the earth again the whole 19 inches would rise again EXPERIMENT V. Figure 8. FIll the Vessel A D G H with VVater to the brim Next thrust down the open orifice of the Tub D A to the bottom and you shall see the VVater ascend in it as high as D according to the first experiment When this is done recline the said Pipe till it ly as B E and you shall find the Pipe compleatly full of VVater Next erect the same Tub again as D A and you shall see the Cylinder of VVater fall down and become shorter as at first For salving this Phenomenon and such like I must suppose this VVater to be 50 inches deep and the Tub I A and B E 90 inches long and the said Tub in reclining to describe the quadrant of a Circle F E G. Now the question is why there being but 50 inches of Water in the Tub while erected there should be 60 in it when it is reclined Secondly why there should be 90 inches of Water in the Tub B E and but 50 in it when it stands Perpendicular as D A If you reply because there are 90 inches in recta linea between the point B and the point E and but 50 between A and D. But this will not answer the case because if you stop the orifice E with the pulp of your Finger before it be erected you will find the Tub remain full of VVater even while it stands Perpendicular and fall down when the orifice is opened Or while the Tub stands Perpendicular stop the orifice I and recline it as B E yet no more Water will be found in it than 50 inches but by unstopping the said orifice the VVater climbs up from R to E and becomes 90 inches Now what 's the reason why it runs up from R to E and why it falls down from I to D I answer then the VVater must runâ—up from R to E because of the inequality that 's between the Pondus of the Cylinder B R and the Potentia of the surface of VVater A B C that supports the said Cylinder For understanding this know while the Tub is erected there is a perfect equality between the weight of the Pillar A D and the force or Power of the surface that sustains it seing a surface 50 inches deep supports a Pillar 50 inches
six inches thick But this seems rather to flow from the disproportion of Magnitudes seing a circular plain 4 inches in diameter cannot receive a Base of a Pillar 6 inches in diameter But this is certain from the very nature of Fluids that in a deep VVater wherein may be distinguished 100 or 1000 different surfaces each one is able to support his own burden and no more EXPERIMENT XIII Figure 17 18 19. FOr making this Experiment take two plain Bodies of Brass or Marble well polished Make them of any quantity but for this present use let each of them be four inches broad square-wise Upon the back part let each one have an handle about six inches long of the same metal formed with the plain it self in the founding if they be of Brass as is represented in this Schematism When they are thus prepared anoint their inner-sides with Oyl or Water and having thrust the one face alongst upon the other with all the strength you have till all the four edges agree two whereof are represented by A B and C D you will find them cleave so closs together as if they were but one Body The effect is this that ordinary strength will not pull them asunder and that under a surface of Water a stronger pull is required than in the Air. That we may deduce some Hydrostatical conclusions from this Experiment let us suppose these two plain Bodies to be united in the middle of the VVater I K P Q that 's 34 foot deep and suspended by a beam or long tree T V existing in the Air near the top of the VVater by a chord S E passing between the middle of the beam and the end of the handle at E. Suppose next a great weight of Lead R 350 pound to be appended to the end of the handle at H of the under plain Body C D N O. This done I affirm that the beam T V neither sustains the under plain Body C D N O G H not the 350 pound weight of Lead R that hangs down from the handle G H. If it be objected that the beam supports the upper plain Body A B L M F E therefore it must bear the weight also of the under plain C D N O G H with the weight R seing they are both united together and cleave so closs as if they were but one Body I answer it supports the one unquestionably but not the other To explicate this Hydrostatical Mystery I must aver three things first that the inferior plain is supported by the upward Pressure 〈◊〉 the lower VVater P Q N O. Secondly that the burden which the beam sustains is not the weight of the under plain but the weight of the 34 foot of Water I K L M. Thirdly that this weight is exactly the weight of the inferior plain and Lead R. But is it not more easie to say that the beam supports both the plains I answer if I say so I can neither affirm truth nor speak consequentially But may it not be said that the inferior plain is supported both by the beam and the lower water P Q N O? I answer this is impossible because one and the same weight cannot be supported totally by two distinct supporters For making these assertions evident I must suppose the superior Water I K L M to be 34 foot deep and to weigh if it were put into a ballance 400 pound and which is unquestionable that the said Water rests upon the back of the superior plain L M. I suppose secondly that the lower Water P Q N O weighs as much and thrusts up the inferior plain with as great weight as the superior plain is prest down with by the superior Water This is evident from former Experiments And lastly I suppose each plain to weigh two pound and the weight of Lead R 350. It is to be observed here that no mistake may arise in the calculation afterwards that though it be said this 34 foot of Water weighs 400 pound yet in it self it weighs but 200 but considering the Pressure of the Air upon I K which is as much it may be truly said to weigh 400. These things being premitted I say the weight that the beam T V sustains is not the weight of the inferior plain and the Lead R but 352 pound of the superior VVater I K L M and consequently that the inferior plain is supported by the lower VVater P Q N O. The reason is because the lower VVater presseth up â—â—th the weight of 48 pound It is in it self 400 pound but being burdened with 352 it cannot thrust up with more weight than 48. Now it pressing up with 48 must ease the beam of 48 and counterpoise so much of the superior VVater and consequently the beam must support only 352 pound of it But put the case you say the weight R were 130 pound 160 pound or 180 pound would the beam be less or more burdened with the superior Water I answer if R be 130 pound then the beam supports only 132 pound of the superior Water for if the inferior be only burdened with 130 the weight of R and with two the weight of the inferior plain then must it press up with 368 and by this means must ease the beam of so much it sustaining 132 pound only According to this compting when the Lead R weighs 160 pound the beam supports only 238 pound of the superior Water If it weigh 180 pound it sustains 218. And if the weight R were taken away the beam supports no more of the superior VVater than two pound To proceed a little further imagine the two Plains to be drawn up 17 foot nearer the first surface I K namely as high as Z W. This done the union breaks up and they presently fall asunder The reason is because the surface Z W is not able to support 352 pound but only 300 which I prove thus If 68 foot sustain 400 then 51 foot must sustain 300. I say 68 and not 34 because as was noted the Pressure of the Air upon the surface I K is equivalent to other 34 foot and therefore though the deepness of this VVater between I K and L M be but 34 foot really yet it is 68 foot virtually and in effect Imagine secondly the surface I K to subside 17 foot namely to Z W. In this case the union is broken also and the lower Plain falls from the upper The reason of this is the same with the former because by what proportion you diminish the high of the superior VVater by that same proportion you diminish the upward Pressure of the lower VVater Therefore if you subtract from the superior VVater 17 foot that weighs 100 pound you subtract likewise 100 pound from the inferior VVater and consequently you make it press up only with 300 but 300 is not able to counterpoise 352. Let us suppose thirdly the superior Plain and the superior Water to be annihilated then I say the
plain had as many holes cut through it answering to the four of the nether Secondly what would folow if the nether plain were intire and four bored through the upper But I shall supersede and leave these to be gathered by the judicious Reader From this Experiment we see first that the broader and larger a surface of a Fluid be it 's the more able to sustain a burden and the narrower it be 't is the less able Secondly that each part of a surface is able to sustain so much weight and no more and no less From what is said we shall only inâ—err this conclusion that equality of hight between Pillars of a Fluid makes equal Pressure and inequality of hight makes unequal Pressure Therefore 't is no matter whether they be gross or small thick or slender provided they be all of the same Altitude EXPERIMENT XIV Figure 20. THis Schematism represents a Vessel full of Water 8 foot deep E F is a Glass-Pipe open at both ends about 9 foot high and one inch in Diameter A B C D is a Vessel of Glass or of any other metal thorow whose orifice above the said Pipe comes down B H I is a Pipe going out from the said Vessel crooked with a right angle at H that the orifice I may look upwards That some Hydrostatical conclusions may be inferred from this Experiment fill the lower Vessel A B C D with Quick-silver almost then pour in as much Water above it as will fill the space A B H leaving from H to I full of Air. Next thrust down the orifice of the Pipe E below the said Water and Mercury till it rest upon the bottom C D. Lastly stop well with cement the passage of the lower Vessel through which the Pipe came down that neither Air nor Water may go out or come in These things being done let down this Engine to the bottom of the large Vessel which as was noted is full of VVater from M N to K L 8 foot and you will find the Mercury to rise in the Pipe from A B to G 6 inches and more The reason is because there is a Pillar of VVater K I that enters the orifice I and presseth down the Air from I to P 3 inches which before was 6. This Air being so burdened instantly presseth forward the VVater H B A and this pressing the surface of the stagnant Mercury A B causes the liquor run up the Pipe from A B to G 6 inches The reason why it riseth 6 inches is this between the surface of the stagnant Mercury A B and the top of the Water L O K are 84 inches Now Water being 14 times naturally lighter then Mercury there must be 14 inches of Water required for sustaining one inch of Mercury and consequently 84 for supporting 6. For a second trial lift up the whole Engine to the top of the Water and you will find the 6 inches of Mercury B G sink down and become no higher within the Pipe than the surface of the stagnant Mercury A B without The reason is because by coming up above the Water the Pressure of the Water K I is taken away from the orifice I by which means the comprest Air H P extending it self to I liberats the Water A B H of the Pressure it had and this freeth the Mercury of its Pressure and so the 6 inches falls down For a third trial stop closely the orifice I and let all down as before In this case you will find no ascent of Mercury from B to G because the Water K I cannot have access to thrust down the Air from I to P as formerly For a fourth open the said orifice I while the Engine is below the Water and you will find the Mercury rise from B to G because the Pillar of Water K I hath now access to press For a fifth trial stop the orifice I and bring up all to the top and you will find the six inches of Mercury B G suspended as if the Engine were under the Water The reason is because the stopping of the orifice keeps the inclosed Air P H under the same degree of Pressure it obtained from the Water K I. For a sixth proof open the same orifice I while the Engine is above the Water and you will find the six inches of Mercury fall down because the imprisoned Air H P obtains now its liberty and expanding it self from H to I eases the Water B H of the burden it was under For a seventh pour in 14 inches of Water at the orifice F till it rest upon the top of the Mercury at G and you will find one inch fall down Pour in as much and two inches falls down In a word pour in as much Water as will fill the Pipe to O and you will find the whole six inches fall down The reason is because the Water K I is not able to sustain both the six inches of Mercury and the Water that 's poured in any one of them being able and sufficient to counterpoise it For an eighth trial empty the Pipe of the said Water and after the Mercury is ascended from A B to G as formerly suck out the whole Air between G and F and you will find the Mercury to rise from G to R 29 inches The reason of this is evident from the Pillar of Air S K that rests upon the top of the Pillar of Water K I for by sucking out the said Air you take away the pondus or weight that counterpoised the weight of the Pillar S K therefore it finding its counterpoise removed presently causeth the Water K I to enter farder within the crooked Pipe till it hath prest up the liquor to R. For a ninth trial take the six inches of Mercury B G and put them into the scale of a ballance then take as much Water as will fill the Tub between A B and O and put it into the other scale and you will find a most exact counterballance between them The reason is because if the Water K H or a Pillar of that hight be able to raise and counterpoise the Mercury B G then must as much Water as fills the Pipe betwen B and O be the just weight of it The reason of this consequence is because these two Waters are of the same weight therefore if the one be the just weight of it the other must be so too If it be said that the Water that fills the Pipe between B and O is far thicker then the Water K H therefore they cannot be both of one weight I answer equality of altitude in this Ballance of Nature is equality of weight therefore seing the one Water is as high as the other they must be both of one weight If it be said that a Pillar of Water between K and H cannot counterpoise the six inches of Mercury B G both being put into a ballance and the reason is because the one is thicker than the
much Mercury as would fill between X O and Z F. For understanding the third remember as was noted before that Fluid Bodies counterpoise one another only according to altitude therefore 't is no matter whether the Tubs be wide or narrow If it be enquired how can one and the â—ame Water counterpoise two Fluids of different weights To say that Fluids counterpoise one another according to altitude doth not clear the difficulty for it still remains to be asked why they counterpoise one another after this manner Therefore it seems that if the Water raise the Mercury from C to E in the wide Pipe it must raise it in the narrow one from D to K. For answer consider first that as there are here two Pillars of Mercury C E and D G within the two Tubs so there are here also two Pillars of Mercury A P and B Q under the two orifices upon which the said two Pillars stand and rest Consider secondly that the Potentia or force of the Pillar A P is just equal to the Pondus of the Pillar E C A Item that the Potentia of the Pillar B Q is equal to the Pondus G D B. Thirdly that the Potentia of A P. is most exactly equal to the Potentia of B Q and the reason is because their tops A and B are parts of the same horizontal surface I say then if A P be equal to E C A and B Q equal to G D B and A P and B Q equal among themselves then must E C A be equal to G D B. The same Water then doth not counterpoise two Bodies of different weight I grant E C A to be far heavier than G D B while they are weighed in a pair of scales but the one is not heavier than the other as they are weighed in this ballance of nature From what is said we see first that in VVater there is a Pressure and a considerable weight This is evident from the rising of the Mercury VVe see secondly that Fluids counterpoise one another only according to Altitude Thirdly that when a lighter Fluid presseth up a heavier there is no more prest up of it than is the just weight of the pressing Fluid because the Mercury E C is just the weight of the VVater that presseth upon X Y O. That 's to say the part of the surface C is no more prest with the Mercury E C than the part X is prest with the VVater L Z X. Fourthly if Mercury were 28 times heavier than VVater only three inches would be prest up if it were but seven times heavier the altitude would be at S 12 inches above C. Fifthly it 's as easie for a large part of a surface to sustain a large Pillar as 't is for a narrow part to sustain a narrower Pillar because A P sustains E C A as easily as B Q sustains G D B. Sixthly that in Fluids there is a pondus and a potentia as is clear from the potentia of A P that sustains the pondus of E C A. The VVater likewise that sustains hath a potentia and the Mercury E C is the pondus of it Seventhly that there is alwayes equality of weight between the pondus and the potentia So is the potentia of A P equal to the pondus E C A. Eighthly that the pondus begets the potentia So the weight of the VVater begets the potentia that's in A P. For make this VVater deeper and you augment the potentia of A P. If you subtract from it the potentia of A P grows less by proportion Or the weight of E C A may be said to beget the potentia of A P. To proceed a little further let us suppose the Air H E to be removed In this case the Mercury rises 29 inches higher than E or 35 above C even as high as S. In the narrow Tub it will climb up to K if you take away the Air I G. This comes to pass by vertue of the Pressure of the Atmosphere that rests upon L N. From this we gather ninthly that there is a counterpoise between the Air H E and the weight of the Air that rests upon L N and that a slender Pillar of Air is able to counterpoise a thicker for H E is far narrower than L N. Tenthly that the Pressure of the Air can be communicated thorow divers kinds of Fluids because the weight that rests upon L N is sent down thorow the VVater L Z X and down thorow the stagnant Mercury and thrusts up the Liquor from A to S 35 inches Eleventhly that a lighter Fluid may be made to press with greater burden than a Fluid naturally heavier because the weight of the Air upon L N raises 29 inches of Mercury but the VVater raises only six VVe see twelfthly that Fluids have a sphere of activity to which they are able to press up themselves or Fluids of different kinds because first the stagnant Mercury can raise it self no higher within the Pipe than it is without Next the 84 inches of Water can raise the Mercury no higher than E. Lastly the weight of the Atmosphere can raise the Mercury no higher than S 29 inches above E. For another trial take out from among the Water the two Pipes and stopping closely the two under orifices fill them with Mercury to the brim Then thrust them down as before and open the said two orifices while they are below the surface X Y O and you will find the whole Cylinder fall down from H to E and there halt and the whole Cylinder in the narrow Pipe falls down from I to G. Or if you please before this be done stop closely the orifice H and the orifice I and you will find the Mercury go no further down than S by opening the orifice A and no further down than K by opening the orifice B. This leads us to a clear discovery of the reason why the Mercury subsides and sinks down from the top of the Tub in the Baroscope to the 29th inch whatever the diameter of the Pipe be And this lets us see that the Mercurial Cylinder is suspended by the Air after the same manner that the Mercury E C is suspended after and that there is no more difficulty in the one than in the other EXPERIMENT XVII Figure 23 24. THis Schematism represents a Water 30 fathom deep Under the first surface A there are six imaginary as B C D E F G every one whereof is five fathom below another There are here likewise two Glasses each one 12 inches high and 5 inches broad like unto these wherein Wine Sack or Brandy is preserved The Glass G M hath its orifice G upward The other Glass is compleatly open below without a narrow orifice For making Experiment take a long chord as long as the Water is in deepness and knit the end of it round about the neck of the Glass at G. Take another line of the same length and
Sink a man may perceive distinctly what is lying in the bottom so clear and transparent is the Air of it but when the Damp is gone the Medium is not so clear In temperat and cold weather the Damps are not so frequent From this Sink in soft winds or in Northerly winds or when it blows from East or North-east the Damps are driven away OBSERVATION II. JUpiter upon Wednesday night at eleven a clock being 24 of November 1669 had the following position with the stars of Gemini He was so near to the Star C that to appearance the points of his rayes did touch it This Star by looking upon the material Glob is fixed in the very Zodiack and in the 13 degree of Cancer and is the very navel of the following Twine The Star A is Castor The Star B is Pollux The star D is fixed in the forefoot of the following Twine From this place he moved with a retrograde motion till he came to the 5 of Cancer about the 20 of February 1670 and from that time became Direct in his motion and so upon the 27 of March 1670 at 9 a clock he was in a right line with Canis minor and the brightest Star in Auriga and was in a right line with the eastmost shoulder of Orion and Castor in Gemini or with that Star when South-west that 's highest and West-most OBSERVATION III. IT is written in the History of the Royal Society that such a member of it whose name I have forgotten hath found out among many other curious inventions this namely a way for knowing the motion of the Sun in seconds of time but is not pleased to reveal the manner how Because such a device may be usefull in Astronomy and likewise for adjusting the Pendulum Clock I shall therefore briefly shew the manner and way how such a thing may be done as I have tried it my self I took an Optick Tub about 12 foot long only with two Convex-glasses in it and did so place it in a dark room by putting the one end in which was the Object-glass without the window and keeping the other within that I caused the beams of the Sun shine thorow it which were received upon a white wall four or five foot from the Tub. This image which was perfectly round and splendid did move alongst the wall very quickly so that in a minut of time it did advance seven inches and a half which will be the eight part of an inch in a second a motion very sensible Now this beam that came thorow the Tub and lighted upon the wall would not have moved one inch in a minut if it had wanted the two Glasses for as they magnify and seem to bring nearer the Object so they quicken the motion of it In a word by what proportion the Object is made more by that same proportion is the motion quickned 'T is to be observed that the longer the Tub be the motion is the swifter for as the longest Tub doth ordinarily most magnify the object so doth it most quicken the motion Next the farther distant the white wall is from the end of the Tub the larger is the image and contrariwise the nearer it be it is the less Thirdly the farther the wall be from the end of the Tub the circumference of the image is the more confused and the nearer it be it is the more distinct Fourthly the darker the room be it is so much the better Lastly this trial may be made with ordinary Prospects of a foot two foot or three foot long which will really do the thing but not so sensibly unless the glasses be very good As to the use of this device in Astronomy I shall not say much But shall only mention what it may serve for in order to the Pendulum Clock For this cause let a man choise a convenient room with a window to the South wherein this Tub may be so fixed that it mayâ—ly just or very near to the true meridian and may move vertically upon an axil-tree because of the Suns declination every day Then at a certain distance from the end of it fix and settle a large board of timber smooth and well plained and well whited for receiving the image In the middle of this board draw a circle with Charcoal equal in diameter to the circle of the image Now this being done you will find that assoon as the west side of the Sun begins to come near to the Meridian the image begins to appear upon the board like the segment of a circle and grows larger and larger till it become perfectly round Now in the very instant of time wherein the image and the circle are united set the wheels of your Clock a going from the hour minut and second of XII To morrow or 3 or 4 dayes after when you desire to make an examination wait on about 12 a clock when the Sun is coming to the Meridian and you will find what the difference is If the Clock go slow observe assoon as the image is united with the circle which you will perceive in a second of time the variation that 's to say how many seconds interveens between that second wherein the union fell and that second that closes XII hours in the Clock If it go fast observe how many seconds passes from that second that ends XII hours and that wherein the image of the Sun is united with the circle which if you do you will know exactly what the difference is even to a second But without this you will find great difficulty to know the variation in 15 or 20 seconds especially in a common Dial. But here you will see distinctly the image of the Sun move every second of time the eighth part or the sixth part or the fourth part of an inch according to the length of your Tub and goodness of your glasses 'T is to be observed that in adjusting the Pendulum Clock respect must be had to the table of Equation of dayes commonly known in Astronomy For if this be not it is impossible to make it go right and that because all the natural dayes of the year are not equal among themselves that 's to say the time that 's spent by the Suns motion from the Meridian this day to the same Meridian the next day is not equal but is more or less than the time spent betwixt Meridian and Meridian a third or fourth day after For instance the Sun this day being 11 of Iuly comes sooner to the Meridian by three seconds of time than he came yesterday Within 9 or 10 dayes suppose the 22 of Iuly he will be longer in coming to the Meridian by 4 seconds than upon the 21. This difference I grant in short time is not sensible yet once in the year it will amount to more than half an hour This inequality of dayes arises from two causes First from the Suns eccentricity whereby he moves slowlier in one part of the
so much skill in these things ye may come to gain the repute of being more fit to be Coal-hewers than Schollars as if the knowledge of such things were not a part of Natural Philosophy It seems he hath either forgotten the common definition or else hath never known it that Physica est Scientia Coâ—poris Naturalis He subâ—oyneth Ye might have let alane the precarious principles and imaginary Worlds of Descartes till yowr new inventions had made them so for it man be telled yow Descartes valued the History of Nature as much as any experimental Philosopher ever did and perfected it more with judicious Experiments than ye would do by all appearance in ten ages But I pray you Sir did Des-cartes and Epicurus and the like found their Philosophy on Natural History and not rather upon their own precarious principles and therefore have quite missed the mark and method that was requisite for the advancement of Learning and have been so far from grasping Nature that it hath flowen out from among their hands As for what he talketh of Des-cartes perfecting Natural History by Experiments if he had done it as the Poet saith in another sense Non mihi res sed me rebus componere conor he had done right But when he took pains on these to force them to a compliance with his own fancies was not this to study Natural History as Hereticks do the Scripture and to be a Fanatick Philosopher and a fit Master for the like of you The Proteus of Nature must be bound with stronger Chains then the fantastick Nugae of Des-cartes before he will tell his secrets The vanity of whose method may be seen in the Epicureans who having laid down this precarious principle that the sense cannot erre do turn themselves into so many shapes to prove that the Sun is no bigger than a blew Bonnet In end after he hath given a Fling at my labours in Glasgow Colledge about Universale and Ens rationis which I am not afraid he shall come the length of in haste for ought I can learn he falleth foul upon the two Lines I cited out of Iuvenal in the close of my answer to a passage in a Philosophical Transaction the Lines are Câ—jus sapientia mâ—nstraâ— Summos posse viros magnaque exempla datâ—ros Vervecum in patriâ crassoque sub aëre nasci Of these Lines he writeth thus Of which saith he the sense is not understoodâ— except ye make your self the summus vir and us all Verveces I suppose this may be the great credit that ye say ye have laboured to gain to your Nation viz. to get us all the honourable Title of Weathers But Reader had these Learned Clerks been as skilful in Rhetorical Composition and Resolution as in Algebraical they would not have made such an Inference for the Argument is à minori ad majus Nor was it ever intended for another end As for the honourable Title of Wedders which they alledge I have gained to them I cannot indeed affirm it for if I should some surely would judge me to have wronged them as much in this as I have done them right all alongs But that thou mayest know Reader something more of the temper of those persons I have to do with in this matter take but the following words of one of them as they are transcribed out of a Letter written with his own hand to me after I had written to him a friendly Letter for obtaining the concurrance of his acquaintance for advancing my Book And they promise to wit the Masters promise ye shall not want their concurrence whereof ye may be sure especially having here your friend Mr. Gregory your Cousin and me here to put them in mind This is all at present from Sir your real friend and servant Now what shall be thought of one who will speak so fair to your face and yet cut you with so many invectives behind backs let any man judge Astutam vapido servat sub pectore vulpem Hic niger est hunctu Romane caveto But to give a further discovery of him in the year 1661 a certain ingenious Gentleman that had not been bred a Schollar by his own industry advanced so far in the Mathematicks that he was able to set forth an Almanack for which ingenuous and ingenious men should have commended him But this Author with another though he had never injured them and without advertisement fell upon him like a couple of Mastives upon a harmless Passenger as if they would have worried him in his reputation in a Prâ—gnostication they set forth rateing and abusing him out of measure all the cause being some alledged mistakes they thought they found in some of his calculations and in a Table in the end of the Almanack which he calleth perpetual and which they say though falsly that it will not hold What had that righteous man deserved at their hands to be so abused in Print by them But that the desigâ— is palpable the raising of reputation to themselves upon the ruine of the names of others And yet one of them many years after was necessitat for fear of bodily harm to crave him pardon with humble offer to his knee In the Prognostication he would needs play the Poet in his Chronology which the person whom he wronged might have found more fault with with better reason than he could do with him for his Calculations What a stranger he is to the more polished part of Learning for all his high pretences these Verses will abundantly testify some whereof follow that thou mayest know the rest Tanquam ex ungue leonem Since that the Iulian period firstâ—began Since that of nought the Lord created man He should have said Since that of dust the Lord created man He addeth Since Israel from Egypt Land did flee Since in Canaan he made Hams sons to die Since Romulus did build his stately Roma Since Nabonassar hence is that ancient ara Since Gregory helped the Calendar forlorn c. Mark Reader these Verses are of five feet at least they should be so but how far he is from observing the Precept of that great Master of Poets Primum ne medio medium ne discrepet imo Will appear from his close Since fair Lucina fulfilled the Golden Number Since glistering Phoebus augmented Sundays Letter Euge Poeta It may be he will say every man is not born to be a Poet. I answer If the Gentleman whom he reviled failed in a calculation he ought to have been born with and encouraged for there are many things that even a mediocrity is commendable in but Poesie is none of these Mediocribus esse Poetis Non Dii non homines non concessere Columnae However for this he may assure himself that Perque Poâ—tarum nâ—nquam celebrabere fastos But I leave him to the Sâ—tyâ—ists of the time Quo illustrius vapulet for his never being seen farder in Print than by a railing Almanack and ridiculous Verses the better whereof might have been made by the Laird of Dysert 'T is like this Antagonist will set his Plumbeous Cerebrosity a work to rifle some of my Writings and shake his head when he is put to a demur as ever a man did a bottle for Sack but though he should and I have nothing of his but an old Prognostication of the Year 1661 to ripe up yet who knowes but I may meet with some of his Bajan-notes or some of his wonders about Ens Rationis and Genus Logicae that he is now sweating at I am indeed at some disadvantage while he only letteth a flisk at me from under deck Though I have been a little sâ—ell in this reply yet 't is no wonder considering what a barbarous and uncivil Pisle I met with which I shall keep for a reserve I desire to live peaceably with all men Neither shall I be soon provocked so long as they keep within the bounds of civility If that be observed I shall thank them for any mistake they shall let me see in my writings if done with reason and without railing FINIS