down by degrees The cause of this Phenomenon is not cold as some might judge but the strong Bensil of the Air within the Ark that so presseth upon the surface of the stagnant Water that it drives it up If you take with you a Weather-Glass hermetically sealled no such thing will follow because the outward Pressure is keeped off 'T is not then cold that 's the cause but weight By the way take notice that all common Weather-Glases are fallacious and deceitful because the motion of the Water in them is not only caused by heat but by the weight of the Air which sometimes is more and sometimes less as frequently I have observed and as hath been observed by others This difference is found by the alteration of the altitude of the Mercurial cylinder in the Baroscope which is more and less as the Pressure of the Air changeth In fair weather and before it comes the Mercury creeps up In foul and rainy weather and a pretty while before it fall out it creeps down Because in fair weather the weight of the Air is more than in rainy and dirty weather December 13. 1669. I found the altitude 29 inches and nine ten parts of an inch at this time the heavens were covered with dry and thick clouds and no rain followed March 26. 1670. I found the altitude no more than 27 inches and nine ten parts at which time there was a strong Wind with rain Between these two termes of altitude I have found the Mercury move near a twelve moneth 'T is a most sure prognosticator for if after rain you find the Mercury creep up in the morning you may be sure all the day following will be fair notwithstanding that the heavens threateneth otherwayes If after fair weather the Mercury subside and fall down a little you may be sure of rain within a short time though no appearance be in the present It falls down likewise when winds do blow What the true cause is why there is such an alteration in the Pressure of the Air before foul weather and fair and in the time of it it is not easie to determine But we proceed Trial likewise might be made by firing a great piece of Ordnance above whether the report would be heard below the Water or not This would determine the question whether Water be a fit medium for conveying sound as Air is Item whether or not the Sea water be fresher at the bottom than near the top which is affirmed by some Item whether sounds be as distinct in such a small portion of Air as they are above This might be tried with a Bell of a Watch. If need were a little chamber Bell might be hung within the Ark and a small chord might pass up from it through the cover whereby the persons above might by so many tingles speak such and such words to the Diver I have demonstrated before that though there were a little narrow hole made in the cover above yet neither Air would go out nor Water come in If a man were curious he might have a window not only in the sides but in the roof above covered with a piece of pure thin Glass thorow which he might look up after he is down two or three fathom and see whether there appeared any alteration in the dimensions of the body of Sun or not or seemed nearer We now come to infer some Hydrostatical conclusions as from former Experiments We see then first that in Water there is a pressure namely from the strong Bensil of the Air within the Ark that groweth stronger and stronger as the Water groweth deeper and deeper We see next that the pressure of the VVater hath an increment because the further down the Ark goeth the Air is the more bended Thirdly two Fluids cannot be contiguous one to another unless both of them be under the same degree of pressure because the Air of the Ark and the Water that creepeth up within the mouth of it are perpetually under the same degree of power and force whatever the deepness be Fourthly that in Fluids the pressure is uniform because the Air of the Ark and the Water without press most equally one against the other Fifthly the more that the Air is bended it is the more difficult to bend it and consequently that the diminution of the quantity is according to unequal proportion Sixthly that when the Ark is down 34 foot the Bensil of the Air is doubled and tripled when it s down 68 foot because the pressure of 34 foot of VVater is as much as the whole pressure that 's from the Atmosphere If it be enquired how much weight rests upon the palm of a mans hand when the Ark is down about 68 foot I answer the pressure of the Water upon a mans hand at that deepness with the pressure of the Air above will be equivalent to the weight of a pillar of Mercury 87 inches high and three inches thick which will exceed in real weight 200 pound If so much rest upon the palm how much must rest upon the rest of the parts of the body Let us suppose then the quantity of the palm to be found in a mans skin 200 times then must he suffer as much pressure and actually support as much burden as will amount to 40000 pound weight Seventhly our bodies may be under a huge pressure and yet that burden not perceptible as is evident from the Diver who findeth little or no weight while he is under the Water Or if there be any Pressure found it 's not comparable to that which really is Eighthly when a man is 14 or 15 fathom down at every inspiration and expiration his breast and belly must lift up the weight of 1800 pound because if the whole burden be 40000 the weight that rests upon the breast and belly will be about 1800. Ninthly that between every inspiration and expiration there happens a perfect counterpoise namely by the Air that goeth into the lungs and the outward Air of the Ark for if the Pressure of the one were more than the Pressure of the other there could be no motion of the lungs Tenthly when a man draweth his breath the Air cometh not in by suction but by pulsion For this cause though the VVind-pipe were stopped yet a man might live by having a hole in his side going into the lungs Lastly that there is no such thing as suction properly and therefore the motion of all Fluid bodies is caused by Pressure and weight The motion of the blood then thorow the heart is driven and not sucted Infants properly do not suck but have the milk squeezed into their mouth 'T is evident from the sucking-glass that some women use for milking their own breasts for by help of this the Air that guardeth the head of the Pap is removed and so the Air that presseth the parts about and without squeezes out the milk Fig. 25 Pag. 179 EXPERIMENT XIX Figure 26. THis Figure
Poet. Acventâ— velut agmine fâ—cto Qua data porâ—â—â—unt terras turbine perâ—â—â—nt Incubuere mari toâ—â—mque a sellâ—us imâ—s Una Euâ—uâ—que Noâ—â—sque enâ—nt creâ—erque procelâ—â—a Africus vastoâ— volvunt ad littora fluctus Tempectâ—â—â—ine more â—urit tonâ—â—â—â—que trenâ—seunt Ardua terraâ—um â—â—â—pique littora circum Winds at his mutinous â—ands Force their own way and thunder through the strands They take the Sea Eurus and Notus raves And stormy Africus from deepest câ—ves When Tempâ—storage and Joves great Cannons reaâ— The Mountains quake the Plains and every Shoar The first Rule is the further up the Metal goes the Weather inclines to be the Fairer and the further it falls down it inclines to be the Fouler Secondly When it is heighest Fair Weather is universal when it is lowest Foul Weather is universal Thirdly 'T is not so much Fair or Foul Weather actually which influences the Quick-silver as it is the disposition and inclination of the Weather to be Fair or Foul. Note That N. E. and E. Winds even with Raâ—n do raise the Mercury and keep it up sometimes beyond ordinary And as it shews the nature of the Weather so it foretells which is the great excellency of it sometimes a day sometimes two sometimes three or four before any change of Weather come The Metal rises and falls quickly when Fair or Foul Weather is nigh at hand It doth not so much foretel Winds as it is actually influenced by them when they blow in causing the Metal subside and fall down 'T is said that the Ladies and Gentle-women at London do Apparel themselves in the Morning by the Weather-Glass Whatever be in this 't is certain that when a Man riseth in the Morning he may know infallibly what sort of Weather will fall out ere Night It is not possible to make it unerring unless it be mounted and set up by a skilful Hand which few or none can do The inclosed Weather-Glasses are Ten Dallers the open ones Thirty Shillings which are as true None from Abroad are so accurately made Neither any such are sold at so easie a rate They may be transported and carried to any part of the Country and there set up by my Directions The Explanation of the Hygroscope THis second is a curious Invention which I call the Hygroscope The The name is made up of two Greek words Hygros Wet and Scopeo to view or consider because we know by it the several degrees of moisture and dryness in the Air. It is mean to look upon being but the Awin and Beard of a Grain of Oats It is Twisted and Twined by Nature as the Lute String or a Silk Cord is twined by Art It is secured within a round Box whose inside is divided into 24. equal parts There is affixed to the top of it a small slender Glass-Index which goes about with the Awin as it is altered with the moisture or dryness of the Air. The motion is direct or right about following the course of the Sun with moisture and retrograde or left about with dryness It is likewise stationary or standing when the Air is setled as to wetness or dryness It is of all of all things in the Universe so far as I know most affected and sensible of humidity and sâ—â—city Many curious Philosophical Questions do arise from its several Operations which would trouble Oedipus himself to resolve I have found the Index from Wet Air in extremity to Dry Air in extremity make six Revolutions For this cause I have contrived a little Broad with six Circles upon it or rather Spirals divided equally into 24. parts as the inside of the Box is by the help of which a Man may trace the motion of it all the Year over most easily whether it be Direct or Retrograde You will find these advantages by it Wet Air in extremity Dry Air in extremity Air equally moist and dry Wet Air Dry Air. It discovers the least difference of Air between one Room and another It is much influenced with Winds from the North especially in Frost which make it Retrograde and with Winds from the South which make it Direct and move right about In a Years time it makes several Revolutions The motion is most sensible for sometimes in one Night it will alter 90. Degrees oâ— the fourth part of a Circle It not only shews the present temperament of the Air which is a great advantage but foretels Nay which is admirable I have found it sometimes foretel Fair Weather when it was actually Raining It keeps a correspondence with the Weather-Glass There is great difficulty to know what Revolution it is under from Wet Air in extremity or from Dry Air in extremity for fixing the Brass-Pin in its own proper Circle The Husk or Hool of the Mouse-Pea as we call it or the Wild Vetch will make a Hygroscope but it is somewhat dull and slow and goes not so oft about yet very sensible of the Wetness and Dryness of the Air. When the Index of the Hygroscope is altered by the Weather it keeps not a continued motion but sometimes moves backward and sometimes forward yet at length perfects its course right about in so many Months and returns again in so many Among the many difficulties which occur this is one What is the reason why the Awin goes alwayes right about with Moisture and left about with Dryness To say that it is so ordered by Nature is ridiculous The same difficulty we find in the Shells of Snails whose Screw and Spiral line goes right about with the Sun and in the Shells of Sea-Snails commonly called Buckies Some affirm that upon the South of the Line the Shells of these Creatures are screwed left about which is worthy of observation 'T is easie to give the reason why a Lute String turns about such a way with Moisture because while it was twined by the Artist the Wheel or Spindle went such a way about wherewith he twisted it But who can say the like of the Awin seing the great Artist is GOD and Nature whose working and manner of working is unknown to us 〈◊〉 be asked What way goes about the Hool of the Wild Vetch I answer which is a notable Speculation The one Hool goes right about with the Sun by Moisture as the Awin doth and consequently left about with Dryness But the other goes right about with Dryness and left about with Moisture contrary to the motion of its fellow Hool This is seen sensibly by holding them nigh the Fire The same holds true in the two Hools of the Right Pea-cod I suppose that the Hools of Brom-seed may do the like Another Experiment I made with the Hygroscope in placing it within the Receiver of the Air-pump At the very first Exsuction of the Air the Index moved left about most sensibly and by the several Exsuctions which were made one after another it advanced half a Circle about It had been easie to have made it
Pillars of Mercury each one of them 29 inches high it follows of necessity that the Mercury within the Tub must be as high as R. 'T is no wonder to see the Silver halt at R provided RX and ZS were two bulks of Mercury environing the Pipe as the outward VVater environs the wider and narrower Pipe Neither ought any to wonder when the Silver falls down and rests at R nothing environing the Pipe but Air seing the Pressure of the Air is equivalent to the weight of 29 inches of Quick-silver This Experiment is easily made take therefore a slender Glass-pipe of any length beyond 30 inches open at both ends but the lower end Q must be drawn so small by a flame of a Lamp that the entry may be no wider than may admit the point of a small needle or the hair of ones head Then stopping the said orifice pour in Mercury above at the orifice N till the Pipe be compleatly full Next close the said orifice with wet Paper and the pulp of your finger and opening the lower orifice you shall find which is very delightful to behold the Mercury spring out like unto a small silver threed and falling down from the top N shall rest at R the motion ceasing at the narrow orifice Q. This shews evidently that there is not need alwayes of stagnant Mercury for trying the Torricellian Experiment but only when the mouth of the Pipe below is wide for being narrow the silver runs slowly out and consequently subsides slowly above and coming down slowly to R there rests But when the mouth is wide below the silver falls down so quickly that it goes beyond R before it can recover it self which recovery would never be unless there were stagnant Mercury to run up again From what is said we see first that when one part of a surface of Water or Air is more burthened than another the burthened part presently yeelds till it be no more burthened than the other This is clear from the falling down of the Water from E to G which cannot be supported by the part I because more burthened than the rest We see secondly that the element of Air rests upon the surfaces of all bodies with a considerable weight otherwise it could not sustain the Water before it fall down from E to G for if it did not rest upon the surface MH with weight the Water could never be suspended seing the application of the finger to the orifice E is only the accidental cause of this sustentation We see thirdly that according to the difference of natural weight between two Fluids so is the proportion of altitudes between two of their Cylinders therefore Air being reckoned 14000 times lighter then Mercury it followes that the Cylinder of Mercury sustained by the Air must be 14000 times lower and shorter than the Cylinder of Air that sustaines it which appears from this experiment to be true seeing by the Pressure of the Air which is thought to be about 7000 fathom high 29 inches of Mercury is supported between R and X. In a word if Air be naturally 14000 times lighter than Mercury which is very probable then must the altitude of it commonly called the Atmosphere be fourteen thousand times nine and twenty inches that is 406000 or of feet 33833. EXPERIMENT III. Figure 6. WHile the outward and inward Water are of the same altitude withdraw the inward Air EG by suction or by any other device you think fit and you will find the Water rise as high as E which I suppose to be 34 foot above MGH The same Phenomenon happens in taking the Air out of the narrow Pipe FK 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 MH 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 MH 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 MH 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 DEHK The second that 's imaginary is LI six foot below it The third of the same kind is MG six foot lower The fourth is NFO six foot yet lower The last and lowest is ABC There are here also four Tubs or rather one Tub under four divers positions with both ends open After this Tub DA 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 EF 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 EF. Again lift it further up till it have the position of the Pipe HG then shall you find the Cylinder of Water become yet shorter Lastly if it be scituated as the Pipe KI the internal Water becomes no longer than KI 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 NO 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 NO 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 GH in this case the Cylinder of Water within it becomes yet shorter even no longer than GH 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 KI in this case the Water within it becomes no longer then KI the surface LI 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 ABC then in the next NO and more in this then in the surface MG and more in this then in LI. 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
orifice M coming up from D some inches of Water falls out as will be found by experience Suppose then that of four foot six inches fall out if this be then the inclosed Air between P and T must be six inches longer if this be then of necessity the Bensil of it must be proportionably remitted and slackened whence follows by Metaphysical necessity that it cannot burden the Water PM with as much weight as it had and consequently the surface of Air cannot be so much burdened It must then be no more buâ—dened with them both together than it is with the single Pillar of Air YN If then the Water PM be three foot and an half the weight of the enclosed Air TP must be exactly the weight of thirty foot of Water and an half From this experiment we see first the Pressure of the Air for by it the Water OI is suspended and by the same pressure is the Water PM suspended We see secondly that in Air there is a power of dilating it self and that this dilatation never happens without a relaxation of the Bensil We see thirdly that one Fluid cannot sustain another unless the Potentia of the one be equal to the Pondus of the other as is clear from the Aërial surface that cannot sustain the whole four foot of Water but suffers six inches of it to fall out that the Pondus of the rest and the Air above it may become equal to its own Potentia We see fourthly that Fluid Bodies have not only a power of pressing downward but of pressing upward likewise as is clear from the Water OI that 's suspended by the Air pressing down the surface of Water HIK It presseth upward also while it supports the Water PM This Experiment also answers a case namely whether or not it is alwayes needful to guard the orifice of the Tub of the Baroscope with stagnant Quick-silver I say then it is not alwayes needful provided the orifice be of a narrow diameter for experience tells that while it is such the Mercury will subside and halt at 29 inches above the orifice though no stagnant Mercury be to guard In making this trial the orifice must be no wider than may admit the point of a needle Or suppose it to have the wideness of a Tobacco-pipe yet will the Mercury be suspended though the end be not drowned among stagnant Quick-silver even as the Water PM is kept up without stagnant Water about it For trial of this you must first let the end of the Pipe be put down among stagnant Mercury and after the Cylinder is fallen down to its own proper altitude lift up the Pipe slowly till the orifice come above the surface and you will find provided you do not shake the Pipe the Cylinder to be suspended after the same manner immediatly by the Air as the Water PM is EXPERIMENT VII Figure 10 11. TAke a Vessel of any quantity such as ABCDE and fill it with VVater And a Glass-pipe such as GFD of 15 or 20 inches long of any wideness closs above and open below Before you drown the open end among the VVater hold the Glass before the fire till it be pretty hot and having put it down you will see the VVater begin to creep up till it come to F where it halts The question now is what 's the reason why the VVater creeps up after this manner 10 or 12 inches above the surface AB I answer the heat having raâ—ified the Air within and by this means having expelled much of it and the Air now contracting it self again with cold the VVater ascends being prest up with the weight of the incumbing Air resting upon the surface of Water AB There is here surely an inequality between a Pondus and a Potentia that must be the cause of this motion I judge then the inequality to consist between the weight of the Air within the Pipe and the surface of Water CDE To explicate this I must suppose the Pipe to be thrust down cold in this case little or no Water can enter the orifice D. And the reason is because the Pondus of the Air within the Glass is equal to the Potentia of the surface CDE But when the Pipe is thrust down hot much of the Air having been expelled by the heat and now beginning to be contracted by cold the Pondus of the Air becomes unequal to the Potentia of the surface and therefore this being the stronger party drives up the Air within the Glass till by this ascent the Pondus of the Air GF and the Pondus of the Water FD together become equal to the Potentia of the surface CDE that sustains them For a second trial bring a hot coal neat to the side of the Glass between G and F and you will find the Water to creep down from F toward the surface AB and if it continue any space it will drive down the whole Water and thrust it out at D. To explicate this I must suppose that heat by rarifying the Air within the Glass intends and increaseth the Bensil of it and the Bensil being now made stronger there must arise an inequality between the Pondus of the said Air and the Potentia of the surface CDE the Air then being the stronger party causeth the surface to yeeld By comparing this Experiment with the former we see a great difference between the dilatation of Air of its own accord and by constraint For while it is willingly expanded the Bensil begins to grow slack and remiss and loseth by degrees of its strength even as the Spring of a Watch by the motion of the Wheels becomes remiss But when the dilatation is made by heat and the Air compelled to expand and open it self the Bensil becomes the stronger and the Pressure the greater Notwithstanding though the Bensil of this inclosed Air GF may be made stronger by heat to the expulsion of the Water FD yet if this rarefaction continue any time the Bensil becomes dull and slack And the reason is because Air cannot be expanded and opened to any quantity an inch cannot be dilated and opened to an hundred or to a thousand neither can the Bensil of it be intended and increase to any degree v.g. from one to 20 30 or 100. And therefore as the expansion grows the Bensil must at length slacken But if so be the Air were inclosed as in a bladder knit about the neck with a string then the more heat the more Bensil for in this case there is a growth of Pressure without dilatation And sometimes the Bensil may be so intended with the heat that the sides of the bladder will burst asunder From this Experiment we see first a confirmation of the 21 Theorem namely that there may be as much Bensil and Pressure in the smallest quantity of a Fluid as in the greatest as is clear from the Bensil of the Air GF which in effect counterpoiseth the weight of the whole
and the thing that is moved Secondly you must consider the motum to have a pondus or weight in it and the movens to have a potentia or power wherewith it moves that weight Thirdly that as the thing that moves hath a power or force in it self whereby it moves so the thing that is moved hath a power or force in it self whereby it resists the motion Fourthly that sometimes the resistance of the thing moved may exceed the power of the movent as when a Quarrier with a Leaver endeavours to prize up a stone too heavy for him or the power of the movent may exceed the resistance of the weight or both may be of equal power Consider fifthly that as the pondus of the thing moved begins to grow more and more so the power of the movent decreaseth proportionably not absolutely as heat is extinguished in Water by the cold Air when it is removed from the Fire but respectively For example when a man holds a ballance in his hand with six pound in the one scale and but one pound in the other if you add another pound the weight grows more and the power and force of the opposite scale grows less proportionably not absolutely for it still remains six pound but respectively that 's to say six pound is less in respect of four than in respect of five or the resistance of six pound is less two counterpoising it than being counterpoised by one When a third is added the weight grows yet more and consequently the resistance of the opposite scale becomes yet less till by adding the sixth and last pound you augment and encrease the pondus to that same degree of strength that the resistance of the opposite scale is of From these considerations I say the surface of Air FG hath not lost all its Pressure absolutely by raising the Mercury from G to H but only respectively because it still retains 29 degrees of force in it self I say respectively because when the Mercury is raised ten inches the power of the Air which is of 29 degrees of force is less in respect of ten ounce then in respect of five or the power of 29 degrees of force is less being counterpoised by ten ounce than being counterpoised only by five And when it is raised 20 it is yet less in this respect than in respect of ten And when it has raised the Mercury to the greatest altitude H it may be said to have lost all its Pressure seing it is not able by vertue of a counterpoise to do any more Even as six pound in this scale may be said to have lost all its resistance and weight by putting in the other scale first one pound next two pound and then three pound till the last be put in at which time it hath no more resistance Though this be yet it still remains six pound Even so the Air FG still remains of the same force and power while it suspends the Mercury GH that it was of before Likewise the Pillar AB cannot be said to have lost all its pressure absolutely by falling down from A to C but only respectively because the said Pillar CB is still 29 ounce weight I say respectively because in falling down ten inches or in losing ten ounce the weight that 's now but 48 is less in respect of 29 than while it was 58. It is yet less when it hath fallen down other ten because being now but 38 it must be yet less in respect of 29 than 48. And when it hath fallen down to C 29 it may be said to have lost all its weight because it can do no more having respectively lost all its Pressure From what is said we see a clear ground to distinguish in Fluids a pondus and a potentia Secondly that the potentia may sometimes exceed the pondus and contrariwise the pondus may exceed the potentia Thirdly that inequality of weight between the pondus and the potentia is the cause of motion of Fluids Fourthly that the motion never ceaseth till the pondus and the potentia become of equal force This conclusion is not so universal as the rest because the motion may sometimes cease before this be For example when the Air is pressing Mercury up thorow a Tub shorter then 29 inches the motion ends before there be a perfect counterpoise for 20 or 15 inches of Mercury can never counterballance the force and power of the Air. In such a case then there is an unequal Pressure the Air pressing the Mercury more than the Mercury doth the Air. EXPERIMENT VIII Figure 12. TAke the Vessel ABCD and fill it with Water as high as HI Take next a Cylinder of stone FG and drowning the half of it among the Water suspend it with a chord to the beam NO with a ring at E. Now in this case though the stone do not touch the bottom of the Vessel yet the Water becomes heavier than before For discovering the true reason of this I suppose fiâ—st the weight of the Water before the stone be drowned to be 40 pound I suppose next that after the stone is drowned the said Water to weigh 50 pound And lastly the stone to weigh 60 pound I say then the Water must be 10 pound heavier than before because it supports 10 pound of the stone 'T is certain the beam is less burdened by 10 pound than before If this be then surely the Water must sustain it It were great temerity and rashness to averr that neither the Beam nor the Water sustains it which is really to say it is sustained by nothing It cannot be said without ignorance that 10 pound of the stone is evanished and turned into a Chimera If it be said how can such a Fluid Body as Water be able to support any part of the weight of the stone that is such a heavy Body I answer there is here no difficulty for if the imaginary surface KL upon which the 10 pound of the stone rests be able to sustain 10 pound of Water I suppose the stone taken away and the place of it filled with Water then surely it must also be able to sustain 10 pound of the heaviest metal seing ten pound of Lead or Gold or Stone is no heavier than 10 pound of VVater If some say this rather seems to be the reason why the Water becomes heavier after the stone is drowned because it possesseth the place of as much Water as would weigh 10 pound not as was said because the VVater supports 10 pound of it Therefore it may be judged and thought that if the space that the stone occupies were filled with Air or some light Body without sensible weight the VVater would become heavier than before For example if in stead of the stone there were placed a bladder full of wind within the VVater and tied to the bottom with a string that the surface might swell from HI to AB the VVater of the Vessel would become
represents a deep Water whose first and visible surface is FG. The imaginary surface is ELC 34 foot below it ADB is a Siphon working below this VVater with Mercury AEL is a Vessel with stagnant Mercury among which the orifice A is drowned the other orifice B existing among the Water DM is the hight of the Siphon above the line of level which I suppose is 58 inches For making it work stop the two orifices closely and pour in as much Mercury at a hole made at D as will fill both the legs Then stopping the said hole open the two orifices A and B and you will find the liquor run as long out at B as there is any almost in the vessel AEL For evincing this which is the only difficulty consider that if this Siphon were filled with Water and made to work only with Air as is clear from daily experience the liquor would run out constantly at B. Because there is here an unequal Pressure the surface of Air NB being more burdened than the surface ELC but where unequal Pressure is in Fluids according to the 12th Theorem motion must follow I prove the surface NB to be more burdened than the surface ELC because the Water BD is heavier than the Water LD as is evident to the eye The Air B therefore sustaining far more weight than the Air EL must cede and yeeld Next there is here a pondus and a potentia the pondus is the VVater LD the potentia by which it is counterpoised is the Water BD but these are unequal BD being heavier than LD therefore according to the 33 Theorem these two Fluids cannot cease from motion If it be said that the surface NB is stronger than the surface ELC seing it is lower I answer the difference is so unsensible that they may be judged but one Now I say if this Siphon work in Air with Water it must likewise work in Water with Mercury Therefore this Siphon being 34 foot below the first surâ—ace FG the liquor must run out constantly at B. Because there is here an unequal Pressure the surface of VVater NB beâ—ng more burdened than the surface ELC. Though there be more weight in NB than in ELC because it is lower yet because the difference is not so much as is between the weight of BD and the weight of LD it proves nothing Note here that so long as D is within 58 inches of EL C this Siphon will work The reason is because the Pressure of 34 foot of VVater with the Pressure of the Air upon FG are able to raise Mercury exactly 58 inches But if D exceed that hight no Art will make the liquor run out at B. Note secondly that this Siphon will operate with Air and VVater though the top D were 34 foot above M and the reason is because the Pressure of the Air is able to raise a pillar of Water to that hight Note thirdly that if there were an orifice opened at C upon the level line ELC the two Waters would become of the same weight the one not being able to move the other If you bore a hole at R the liquor ascends from R to D and goeth down from D to A and so the motion ends But if the leg AD were six times wider than BD the liquor would not run out at B. I shall answer this in the close From this Experiment we see first that the motion of Fluid Bodies up thorow Pumps and Siphons is not for shuning vacuity but because they are prest up violently We see next that when the Pressure is uniform there is no motion in Fluids but assoon as one part is more prest than another motion begins because this Siphon will not operate if the orifice be made in C but if so be it be in D then the motion begins because there is here an unequal Pressure which was not in the other We see thirdly that Fluids have a determinate Sphere of activity to which they are able to press and no further because this Water is not able to press Mercury higher than 58 inches So the Air cannot raise Water higher than 34 foot If this Water were 68 foot deep the Sphere of it's activity would be 116 inches We see fourthly that in Fluids there is a Pondus and a Potentia and that the inequality of weight between the two is the only cause of motion We see fifthly that as long as this inequality of weight continues as long continues the motion because as long as BD is heavier than LD the motion perseveres We see sixthly the possibility of a perpetual motion in Fluids because the liquor runs perpetually out at B. If it be said the motion ends when the stagnant Mercury AEL faileth I answer this stop is only accidental and not essentially from the nature of Fluids If it be enquired whether or not would the Mercury run out at B upon supposition the shank LD were twice as wide as the shank BD I answer it would If it be said that the one is far heavier than the other namely LD than DB. I answer weight in Fluids is not counted according to thickness but according to altitude EXPERIMENT XX. Figure 27. THis last is for demonstrating the precise and just weight of any Pillar of Air Water Mercury or of any other Fluid body if some of their dimensions be but once knowen AB then is a square Pipe 12 foot high and six inches in wideness full of Water resting upon the surface of Air AC And EG is a square Pipe 12 foot high and 12 inches wide full of VVater resting upon the surface of Air EF. None needs to doubt but the two Waters will be suspended after this manner even though the orifices A and E were downward especially if they be guarded with Water but the demonstrations will be the more evident that wee suppose the two Pillars of Water to be suspended as they are From this Experiment I say first that the Pillar of Air CD is 168 pound weight at least which I prove thus The VVater AB is 168 pound therefore the Air CD must be as much I prove the Antecedent because it 's a Pillar of VVater 12 foot high and six inches thick but every half cubical foot of VVater that containes 216 inches weighs seven pound therefore seing the Pillar is 12 foot it must contain 24 half feet but 24 times 7 is 168. The only difficulty is to prove the Connexion which I do thus from the seventh Theor. all the parts of a Fluid in the same Horizontal line are equally prest but so it is that the part A and the part C are in the same horizontal surface therefore the part A and the part C are equally prest But if the part A and the part C be equally prest the Pillar of Air CD must be as heavy as the Pillar of VVater AB I say secondly that the Pillar of Air FH weighs 672 pound I prove it thus
to their thickness but only according to their altitude Fig. â—â— Pag. 1â—4 Fig. 24 Pag. 152 Fig. 26. Pag. 182 Fig. 27 Pag. 196 AN ACCOMPT OF Miscellany OBSERVATIONS Lately made by the Author of the foregoing EXPERIMENTS OBSERVATION I. IN May 1669 there was need of a new Sink on the east side of Tranent for winning of Coals But while the Coal-hewers were in digging down and had come the deepness of 13 or 14 fathom they were stopped from working by Damps or ill Air that flowed out plentifully from the sides of the sink wherein there were a great number of Cutters or rifts out of which that ill Air came To try the nature and power of Damps I took a dog and fastned him in a bucket with a small roap that he might not leap over and when he had gone down 7 or 8 fathom he presently begins to howl and cry pitifully as if he had been beaten sore with a rod and a little after he begins to stagger and his feet failing him he falls down as one overtaken with the Epilepsy and in going down to the bottom his eyes turning in his head they appeared very shining and clear like two large bright Diamonds Fearing that the Damp should have killed him out of hand he was instantly pulled up from the bottom where he had not tarried 15 seconds of time And when the bucket had come to the mouth of the sink he was pulled out and laid upon the ground to get fresh Air. When he had lien a while as dead he begins at last to gape and gasp and make some respirations as if he had been rather expiring than recovering Next he began to stir and move his feet and after to raise himself upon his knees his head staggering and wavering from side to side After a minut or two he was able to stand upon his feet but so weakly that he was not in capacity to walk or run Yet at last being much refreshed he escaped from us and ran home but slowly In the afternoon the same Experiment was repeated with another dog whose case was the same in all things But after he was perfectly recovered for a further trial we let him down the second time and suffered him to tarry in the bottom of the sink about the space of three minuts but when he was pulled up and taken out we found no symptomes of life in him and so after half an hour and more his body began to swell which ordinarily befalls such who are killed after this manner After this we sent down in the Bucket a little Chicken which when it came near the Damp presently slapped with the wings and falling down turned over and over for a pretty while as if it had been taken with a vertigo or giddiness But by drawing up the Bucket in haste and bringing the Bird to the fresh Air it recovered In the evening we let down a lighted Candle but it was soon extinguished when it came near mid-sink for here rather than in the bottom was the strongest Damp. Lastly we let down by a chord a Brand-iron with burning Coals whose flame was soon put out and after a little while we perceived the red Coals to be extinguished by degrees yet not totally because as the Coal-hewers observed the power of the Damp was not so strong as before These Damps then have their ebbings and flowings which seem to depend upon the weather or rather upon the situation of the winds and their force For 't is observed that a high South-west wind causeth ill Air in this place and that by reason of much wast ground that lies upon the South and South-west hand of this Sink whence are conveyed under ground by secret passages which are nothing else but so many rifts and openings commonly called by the Coal-hewers Cutters corrupted and rotten Air full of sulphurious stems The reason why these passages are open and replenished with nothing but corrupted Air is this the Water that 's ordinarily called the Blood of the Coal being withdrawn with subterraneous Gutters commonly called Levels that are digged and wrought under ground sometimes a very long way for drying of the Mines and the veins of the earth being now empty there succeeds Air which Air by process of time and long standing rots and contracts a sulphurious quality which causeth sudden death Now when the wind is high and strong from the South or South-west that sulphurious Air is driven through the ground and coming to Sinks and Mines where men are working presently infects the place and hinders the work 'T is often observed that the wind and Air under ground keep a correspondence in their motion with the wind above ground and therefore when the wind is in such a point above 't is found that the motion of the Air below runs such a way and the contrary way when the wind above ground is in the opposite point When there is a free passage between the bottom of the two Sinks you may observe the wind come down through the one and running alongst under the ground rise up thorow the other even as Water runs thorow a Siphon For this cause when the Coal-hewers have done with such a Sink they do not use to stop it or close it up but leaves it standing open that the Air under ground may be kept under a perpetual motion and stirring which to them is a great advantage 'T is very strange to see sometimes how much Air and how fresh it will be even at a very great distance namely four or five hundred pace from the mouth of the Sink This could never be unless there were a considerable Pressure and weight in it whereby it is driven forward thorow so many Labyrinths And even in the utmost room where the Coal-hewers are working the Pressure is as great as it is above ground which is found by the Torricellian Experiment In such a case the Air cannot press down thorow the Earth and Metalls therefore the Mercury must be suspended not by a Pillar from the Atmosphere but by the Bensil of it Nay put the case that the whole Element of Air were destroyed and this remaining yet would it be able to support 29 inches To shut up this discourse it is observed by the Coal-hewers that when there is ill Air in a 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 may 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 Zodiack than in another for in Summer when he is furthest from the Earth he goes slowlier back in the Ecliptick than in Winter when he is nearer to it The second cause which is truly the far greater is this because in the diurnal motion of the Sun equal parts of the Aequator does not answer to equal parts of the Zodiack Hence it followes that if the natural dayes be not equal among themselves the hours must be unequal also but this is not considerable By help of such a Tub placed in a dark room it is easie when the Sun is under Eclipse to enumerat distinctly the digits eclipsed Likewise if you take
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 OBSERVATION 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 that Decemb. 13. 1669 one Doctor Beal found the Mercury in the Baroscope never to be so high as it was then That same very day I found the hight of it 29 inches and nine ten parts which I never observed before And though the day here was dark and the Heavens coveâ—ed with Clouds yet no rain for many dayes followed but much dryness and fair weather On Saturday night March 26 1670 I found the altitude no more than 27 and nine ten parts This night was exceeding windy with a great rain On February 1. 1671. I found the altitude 30 inches and the Heavens most clear But in the most part of May
the ground where they are found both in regard of the use they serve for in stead of Level and for rendring the Metals wherein they are found more easie to work in making them yeeld easily to the force of the wedge and leaver Other Metals there are wherein few of these Cutters are to be found and if water be to be conveyed through them there is a necessity of cutting a passage through them for that effect Now this Damp whereof we speak is sound most frequently and most violent in the first sort of Metals viz. in these which are full of Cutters or Rifts which gives some ground to this conjecture of its cause These Spaces which are found in Coal or other Metals as Stone or Till before the Coal begin to be dryed by a Level are full of water which is still in motion as are all subterraneous springs whereof some are more violent some more slow conform to the passage they have to the fountains above ground where they discharge themselves Now for drying these Coals and rendring them workable there is a necessity to cut a passage thorow which that water discharges it self quickly it being large and admitting a great quantity at once by vertue whereof a great field is drained at once and the Sourse not being able to furnish so much water as the Conduit is able to convey these Spaces in the body of the Metals being emptied of Water must needs be filled with Air which Air having little contact and commerce with the great body of Air above ground and so hath little or no motion corrupts in these places and thereby becomes poisonable so that when any Animal is necessitat to draw it and respire by it it choaks them on a sudden just as standing Water which being without motion corrupts and becomes poisonable though haply not in so great a degree as the Air the Air being a body much finer and purer than Water that holding good in it corruptio optimi pessima This is much confirmed by what is before asserted that in the Coals whence the Water is drawn and they drained but not by free-course but by Force as Pumping and drawing by buckets these Damps are seldom or never found because the passage of the Water being forced it does not so suddenly dry the Metals as the other whereby there is alwayes left in these Spaces some Water which being it self in motion keeps the Air also in motion with it and thereby the Air is kept from corruption at least in such a degree as it is in the other Hence we find that in these kinds of Coals the Rooms under-ground are alwayes wet or for the most part they are so whereas in the other there will be no Water found to wash a mans hands and sometimes the Coal through want of Water becomes so dry that it cannot be wrought in great pieces as others but crushes in the very working and when wrought is rendered useless and will not at all burn This puts me in mind of a very pleasant conception of a worthy and learned Person Doctor George Hepburn of Monk-ridge with whom I had occasion one day to discourse on this Subject He is of opinion that the Water is the Mother of the Coal whereby it is preserved fresh and incorrupted and that when the Water is drawn off and this Damp follows it is not the Air which succeeds in place of the Water and is corrupted for want of motion that occasions it But as we see when the corruption of a Liquor within a Vessel when the Mother is gone corrupts the Vessel it self and occasions an ill savour or taste in the Vessel so that the Coal being corrupted by the want of its Mother the Water corrupts the Air in the subterraneous Spaces as in Coal-Mines Sinks Caves and other such like He had likewise another pleasant conception about the generation of Coal judging it to be formed gradually out of another Metal as of Till by the help of Water of which he himself may perhaps give an account And though I be not of his opinion in that matter yet I must acknowledge I was taken with it and shall be glad to see a more full account of it from him than he had access to do in the short conference we had The effects of this Damp are first it hinders the burning of all combustible matter as Candle Coal Pitch Sulphur c. so that if you take a Torch lighted and let it down to a Sink where the Ill Air is prevalent in the time it shall straight extinguish it Or take a Coal which is burning and let it down it shall not only extinguish the Flame but shall make the Coal in an instant dead and as cold as never heat had been in it But the most dangerous effect is its killing of living Creatures whereby many persons have been suddenly killed Some in going down to a Sink where it hath been powerful have fallen out of the Rope and perished Others have been choaked and yet have gotten out by the help of others in a sudden and have remained a considerable time without the least appearance of life but yet have at last recovered Yet it hath been observed that some of these persons that have been so struck with the Damp and recovered have had alwayes some lightness of Brain thereafter and never so settled as formerly This I know to have happened to one whom I have seen so many times thereafter What hath been its effects on some Animals whereof you have made Experiment I leave to the account you have given One thing I shall only mention which to me seems somewhat strange that notwithstanding these Damps are so effectual and causeth so suddenly the death of Animals yet the Ratts which are in some of these places where the Damps are most violent are not reached by them For sometimes when they are so powerful that nothing that lives can enter under ground without sudden death yet they continue there and are not found to diminish even where they have no access to escape by coming above ground Or if it should be imagined they removed to some other place of the ground where the Damp is not how is it they are not as quickly choaked with it as Dogs are and other Animals which at the first encounter are killed If it be inquired how comes it to pass that in these Fields of Coals which are dryed fully as was said and to which these Damps are incident because of corrupted Air that remains within the Body of the Coal or other Metals how comes it to pass I say that they are but sometimes incident and are not alwayes found For clearing this it is certain that even in the grounds where these Damps are most frequent for the reasons above mentioned yet they are only powerful when the Wind blows from such a certain Point as some Chimneys that do only smoke when the Wind is in such an Airth This is