Receiver upon the Exsuction of the Air we observ'd that the Air which was contain'd in the Cavity of the Viol was so far expanded that tho' the Viol was able to contain above five Drachms of Water if filled and distended the empty Bladder which was large enough to hold five Ounces and half a Drachm In which Experiment the expanded Air possessed nine times as much space as it did before Expansion But to measure the Air 's Expansion more nicely we fix'd a Glass Bubble to one end of a Cylindrical Pipe hermetically sealed the Diameter of whose Bore was about a quarter of an Inch and having pasted a Piece of Parchment upon the outside of the Tube which was divided into twenty six equal Parts and mark'd with black Lines we fill'd the Cylinder almost full of Water so that after a few Tryals by inverting the Cylinder and stopping the open End with one's Finger we could perceive that as much Air might be permitted to rise up to the Bubble as was equal in Extension to the Breadth of one of those twenty six Divisions When this was done we fitted the open end of the Cylinder to a Glass Viol which was fill'd with Water to the Height of half an Inch all which being put together into a Pneumatical Receiver after a few Exsuctions the included Air was so much expanded as to extend it self to the Surface of the Water in which Experiment the expanded Air took up thirty one times as much Space as before And this Experiment being repeated in a Cylinder which afforded a larger space for the Air 's Expansion it took up above sixty times the space it did before And repeating the like Experiment with a Glass Pipe thirty Inches long part of it having a Hole in the Cover to stand out through by weighing the Water in a nice Pair of Scales together with the Pipe first with the Bubble of Air included and after when the Tube was wholly filled with Water we found That the Air which possessed but the Space of one Grain of Water had been expanded in the exhausted Receiver so much by its own 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 as to take up 152 times its Space before Extension And since Marcennus affirms That the Air may be so expanded by Heat as to take up seventy times its Space I conveyed a Cylinder of the former Magnitude into the Receiver and found That upon the Exsuction of the Air in the Receiver that in the Cylinder descended down almost to the bottom of it the lower Surface of it being very convex and seeming several times to knock upon and rebound from the bottom of the Viol which was an Argument of the expansive Force of the Air since the Water it depressed upon the drawing out of the Air was much below the Surface of the Water contain'd in the Viol. EXPERIMENT VII What Figure best resists the Pressure of the AIR HAVING got a thin Glass Bubble which was large enough to hold about five Ounces of Water to which was fix'd a slender Neck about the Bigness of a Swan's Quill we moderately exhausted the Air out of the Receiver and then taking it out of the Pump we joyn'd the Neck of the Bubble to the lower Orifice of the Receiver stopping the Crannies with melted Plaster to prevent the Ingress of the Air and tho' the Glass was as thin as Paper yet upon turning the Key of the Stop-Cock and giving the Air included in the Bubble Liberty to expand the Bubble sustained the Pressure of the whole Atmosphere without being broke EXPERIMENT VIII The former Experiment illustrated WE took a Glass Alembick which was large enough to hold about Three Pints represented by the Seventh Figure The Rostrum E being hermetically closed In the Top of the Rostrum was a Hole into which one of the shanks of a Stop-Cock of an ordinary size was cemented the other being fixed with Cement in the upper Part of the Pump which being done and the upper Orifice of the Alembick being covered close with a Plate of Lead exactly adapted to it upon drawing the Air out of the Receiver the Glass presently cracked which Crack is represented by the Line a b and this Flaw extended it self further accordingly as the Air was more exhausted yet this Glass Vessel was near twenty times thicker than the Bubble And that the Figure of the former Glass enabled it so much better to sustain the Atmosphere was further confirmed by suspending one of the Bubbles hermetically sealed in the Receiver which so strongly resisted the Expansion of the Air contained in it as to continue whole when the Receiver was exhausted EXPERIMENT IX A Confirmation of the former Experiment An Experiment to shew that these Phaenomena exhibited in Vacuo Boyliano proceed not from a fuga Vacui c. A Confirmation of the former Experiment c. HAving put the end of a slender Glass Pipe into a Viol which was large enough to contain four Ounces of Water and fixed it to the Neck of the Viol with a Cement of Rosin and Pitch so that the end of the Pipe almost touched the bottom of the Viol as in Fig. 6 this Viol was conveighed into a small Receiver as much Water being put into it as wrought a little above the bottom of the Cylinder the upper End of the Pipe being most of it without the Vessel a Hole having been purposely made for it in the Top of the Receiver The Event of which Tryal was that upon drawing the Air out of the Pump the Weight of the Atmosphere internally pressing into the Pipe and the Spring of the Air within the Receiver not equally pressing against the sides of the Bottle which were exposed to it a Piece of the Bottle burst out of the side of it with such a Force as to crack the Receiver in several Places and having reiterated the Experiment with a round Glass Bubble the Leaden Cover of the Receiver was not only depressed by the Weight of the Atmosphere so as to thrust out one side of the Receiver but the Glass Bubble was cracked into Pieces with such violence as to tear a Bladder which it was encompassed with to keep it from breaking the Receiver in several Places Before I proceed to the next Experiment it may be requisite to advertise That though the larger Receivers are apt upon some Tryals to crack yet they are not rendered altogether useless since when the Air begins to be exhausted the ambient Atmosphere compresses the Lips of the Glass closer together But if the Crack be considerable it may be cemented with a Plaster made of Quick-lime and Scrapings of Cheese ground together very finely in a Mortar and made into a Paste with a little Water which being spread upon a Cloath about three Inches broad must be apply'd to the Crack EXPERIMENT X. Of the Flame of a Candle in a Receiver HAVING suspended a Tallow Candle in our Receiver we found That upon an Exsuction of
wholly freed from Air there was neither any Ebullition nor an appearance of Bubbles yet the Drops of Oyl mov'd in Vacuo after the same Manner as in open Air. Hence it appears that the Motion of the Parts of Oyl depend not in a Dissolution in Vacuo since all Dissolutions are company'd with a production of Bubbles EXPERIMENT VIII May 19. 76. Radishes in a Receiver with Claret HAving cut two Radishes transversly and suspended them all Night in Vacuo over a Vessel of Claret the small End of one being downwards and the other in a contrary Posture all being freed of their Air the next Day I freed two other Radishes from their thick Skin and cutting them transversly suspended them over the Wine as the others in Vacuo upon which immersing them all in the Wine they emitted Bubbles considerably especially those that had been longest in the Receiver From this Experiment we may urge that Bubbles are form'd of Particles of Air contain'd in Water and the Reason why those Radishes yielded most Air whose Skins were not pull'd off is because those Skins are full of Canals and Pores to contain Air in for the forming of Bubbles The Liquor ascended equally in all the Radishes notwithstanding their Postures EXPERIMENT IX May. 4. A small Tube immers'd in Water A Small Glass Tube open at both Ends being immers'd in Water the Water in Vacuo ascended as high as it usually does in common Air but in a little time it was rais'd higher by Bubbles of Water which divided and intercepted the Cylinder of Water in 3 several places besides several Bubbles of Water pass'd out at that End of the Tube which was immers'd One End of this Tube being Hermetically seal'd up the Experiment succeeded after the same manner as when it was open but in the open Air the Water ascended not One thing in this Experiment was very Remarkable viz. That the Water suspended in the Tube yielded no Bubbles but only at the Bottom of the Tube nor did the Cylinder of Water even at the Bottom yield Bubbles when it was rais'd above the Surface of the Water which it was before immers'd in May. 5. The Experiment was repeated but before the End of the Tube was immers'd in Water a Drop which ran over the Superior Aperture of the Receiver fell down to the open End of the Tube and was rais'd two Lines in the Cavity of the Pipe No Bubbles were form'd in half an hour till the Tube was immers'd in Water and then successively they rose one after another In trying this Experiment several times I observ'd that tho' whilst the Tube was immers'd several Bubbles appear'd about the End of it yet when it was rais'd above the Surface of the Water none were to be seen May 6. The Experiment was try'd with an Infusion of Nephritick Wood in which the Success was alike except that in the Infusion when the Bubbles were small they ascended to the Top of the Liquor which is an Argument of it's Thinness and that it hath no Viscocity May 10. I repeated the same Experiment with a Mixture of Spirit of Wine and an Oyl made per Deliquium In which nothing was to be observ'd different from the former but that the Liquor ascended not so high From these Experiments it may probably be inferr'd That the Formation of Bubbles in the Extremity of the Tube depends on aerial Particles which swim in the Water and meeting with some Impediment at their End are kept there till new ones joyning with them form Bubbles EXPERIMENT X. July 18. 76. Beans with Water in an Iron Tube BEANS such as Horses eat being shut up with Water in an Iron Tube 2 days ago to day seem'd unalter'd but the Stopple of the Tube being pull'd back Air and Water broke out which Eruption was succeeded by a bubling Noise which continu'd above an hour July 25. The Iron Tube was open'd a second time and a bubling Noise succeeded as before Whence it appears that Beans contain Air which cannot discharge it self in a Compression till that Compression is remov'd EXPERIMENT XI March 4. 77. Spirit of Sal Armoniack and Copper A Glass half full of Spirit of Sal Armoniack being included in Vacuo with Filings of Copper in it in 15 Minutes it was tinged with a diluted Blew which upon an Ingress of Air in 3 Minutes became vivid and thick April 4. The Liquor having been enclos'd in Vacuo had almost lost it's Colour which it regain'd when the Air was let in again EXPERIMENT XII May 8. Oyl per Deliquium with Spirit of Wine OYL made per Deliquium being shut up in a Receiver with Spirit of Wine swimming upon it when the Air began to be exhausted great Bubbles rose from the Spirit and small ones from the Oyl but in an hour the Oyl afforded Bubbles large enough to fill the whole Diameter of the Pipe in their Ascent and an hour after that they broke out so violently as to strike against the Top of the Receiver May 9. The Experiment being repeated in a Vessel which was longer and narrower I observ'd that the Bubbles which rose from the Oyl were not very large till ¼ of an Inch above the Surface of it and then they were suddenly expanded EXPERIMENT XIII May 3. 76. Aq. Fort. and Spirit of Wine A Mixture of Aqua Fortis and Spirit of Wine being divided into three Parts and each of those included in a distinct Vessel with a piece of Iron one of them was included in Vacuo upon which several considerable Ebullitions succeeded The Liquor when taken out was black and Turbid tho' in the other two it was not alter'd in Colour but only a black Powder was settled in the Bottom Wherefore one of those being included in Vacuo after Ebullitions less violent than those in the Vessel first included the Liquor in a quarter of an hours time being taken out was almost as black and turbid as that first put into the Receiver That in the open Air was not much alter'd May 4. The Liquors shut up in the Receivers appear'd clear and green But that in the open Air bubbled more than the day before and was of a red Colour And all three being shut up in Vacuo the red Liquor afforded larger Bubbles Hence it appears that Spirit of Wine promotes Ebullition in Vacuo EXPERIMENT XIV Jan. 21. 78. Spirit of Sal Armoniack with Filings of Copper A Glass half full of Spir. Sal Armon with Filings of Copper stopp'd with a Leather Stopple was put into a Receiver with unfermented Paste Jan. 22. The Air yielded by the Paste penetrated the Leather which is impervious to common Air which appear'd by the Tincture it gave the Liquor Jan. 25. The Liquor had almost lost it's Colour so that the Particles of Artificial Air are so minute as to penetrate Pores which common Air cannot Feb. 2. The Glass being shut up in a Receiver which admitted Air so
the Liberty of uniting as they ought to form Crystals of a natural Figure which Guess is confirmed because the Crystals which shot in Water where they have room enough and an indifferent Vehicle were more perfect than those which were produced by a Mixture of the nitrous Powder and Saline Spirit where they were forced for want of Room to Cry stalize before they had time to Convene after a manner requisite to make them of a natural Figure and Size But to proceed This Experiment which shews how a Body divided into different substances by Distillation may be again united into an Original Concrete will be a very strong and convincing Instance to prove that the Forms and Qualities of Bodies depend on an essential Modification of their Parts and that the difference observable in particular Substances depends on a different Texture and a Coalition of Parts of different Figures and Sizes so that the Redintegration of Bodies is no more but a restoring of their former Parts into the same Order and Position being Artificially handled so as to acquire their former Sizes and Figures in order to their Coalition Yet this I think necessary to be represented viz. that the Composition of Nitre is so little Organical that it will be hard to judge what success in order to Redintegration may be expected in other Bodies where the Fabricks of them are so curious by Reason of their numerous Ingredients and the curious Contexture of them that the latter is not to be imitated by Art in the Production of Substances much less Organical than the Parts of living Animals Chymical Medicines laid aside too rashly The last Observation I shall make on our Experiment is That from what hath been said it may be thought that some Chymical Medicines may be too Rashly laid aside by some Physitians who suppose that the Menstruums made use of in their Preparations are in some measure mixed with them since besides that those Salts may by care be washed away several Parts of them may be so altered by Corrosion that those associating with other Particles of the Body they work upon may degenerate into an innocent Concrete An Instance of which we have in our Experiment where a corrosive Spirit and a Caustick fixed Salt unite into an innocent Medicine And that Corrosive Salts may in a great measure be dulcified by their acting on other substances is evident in a Mixture of Spirit of Vitriol and Crabs Eyes or any other testaceous Body And again though Vinegar powerfully corrodes calcined Lead yet uniting with it it constitutes a Sweet Body in which the sharpness of Vinegar is perfectly destroyed And tho' it be an Argument usually alledged against the use of Medicines so prepared that from several of them corrosive Particles may be drawn yet since the same may be Effected by the Action of Fire upon Salt-Petre the Objection is as invalid as the general Practice of Physitians can make it CHAP. XI Containing the History of Fluidity WHETHER Fluidity and Firmness might not with more Reason be esteem'd States than Qualities of Bodies or not this is most certain that they are to be accounted the most General Affections of Matter all Bodies being either Fluid or Solid If then these Qualities or States of Bodies be so General it will be of moment to consider the Causes of them and the rather in this place because the Foregoing Experiments of Salt-Petre may serve to illustrate them The Definition of a Fluid Body To proceed then A Body is said to be Fluid because it consists of Parts which easily slip upon one another's Surfaces to and fro when mov'd by Reason of the Porous Interstices which remain betwixt those Parts which they are made up of they not being wholly Contiguous on every side and also because by Virtue of that Motion they spread and diffuse themselves on every side till oppos'd by some Solid Body to the Internal Superficies of which they presently adapt themselves And what Thoughts Epicurus and the Ancient Corpuscularians had of Fluidity will appear from these Verses of his Paraphrast Lucretius Illa autem debent ex Laevis at que Rotundis Esse magis fluido quae Corpore liquida constant Nec retinentur enim inter se glomeramina quaeque Et procursus item in proclive Volubilis extat And indeed we may rationally believe That the Smoothness of their Parts may much contribute to the Fluidity of Liquors as well as the Globular Figures of them tho' there are several Fluid Bodies whose Parts are of Figures very various besides Flame and Air the Figures of whose Parts are very irregular * Bodies whose Parts are less condensed than Water to be esteemed Fluid And here we are to take Notice That to render a Body Fluid there is no need that its Parts should be so closely condens'd as those of Water are since Flame and Smoke may be so manag'd as to resemble Liquid Bodies of the Latter of which we have Proof by blowing Rosemary-Smoke into a Glass-pipe which if when it is fill'd the lower End be stopp'd and the Pipe be held in a Perpendicular Line the Surface of the Fumes will subside till Level and tho' the Pipe be inclin'd several ways yet the Superficies of the Smoke answers to the Horizon till the Glass be further inclin'd and then the Smoke will run along the Pipe like Water dispersing it self afterwards in the Air. But to return to the Cause of Fluidity We conceive that there are Three things requisite to render Bodies Fluid Minuteness of Parts requisute to Fluidity 1. The Minuteness of the Particles which constitute them by which they are dispos'd to an Intestin Motion and to be preserv'd in it more easily as the Parts of Lead Quick-silver and Gold when dissolv'd by a Menstruum are easily rais'd and mix'd with the Parts of that Menstruum Nay Fluidity so much depends on the Minuteness of the Parts of Matter which constitutes Fluid Bodies that the Parts of Antimony dissolv'd and broken into small Corpuscles may be turn'd into Butter of Antimony and that Butter of Antimony is chiefly made up of the Substance of the Antimony is evident since by a Mixutre of fair Water a white Calx will precipitate easily convertible into Glass of Antimony And Nature her self supplies us with further Instances since the very Substance of Bones is by Comminution in the Stomachs of Dogs turn'd into a Liquor And to confirm this Observation I shall add That I knew a certain Gentleman who was a close Student who liv'd for several Days together without the least Drink tho' in the mean time he sweat moderately and easily enough his Urine being agreeable to his Constitution as the Urine of other Men's generally is to theirs But that Solid Substances may yield and be turn'd into Fluids by a Comminution of their Parts may be evinc'd by the Fusibility of Metals since the more the Massy Particles of Metal are broke into small Parts
a Long Leg and a Short One which were so bent as to lye Parallel almost to each other we pasted Papers upon each which were divided by Marks into Inches and each of those Inches into eight Parts and upon pouring Mercury into the Longer Tube we observ'd That the Air contain'd in the Shorter which was Hermetically seal'd at the Top by twenty nine Inches of Mercury was condens'd into half the Space it possess'd before from whence it appears that if it were able in so compress'd a State by Virtue of it's Spring to resist a Cylinder of Mercury of 29 Inches besides the Atmospherical Cylinder incumbent upon that it follows that it's Compression in the open Air being but half as much it must have but half that weight from the Atmosphere that lyes upon it in that Compress'd State But to be more exact See Fig. 4. Plate 2. we took a Tube represented by the Fourth Figure pasting upon the Shorter Leg a Paper divided into twelve Inches and each of those into Quarters and another upon the Longer Leg which made up several Feet which were likewise divided into Inches and those subdivided again into Quarters The Tube being thus Mark'd the Lower End was plac'd in a Wooden Box that the Mercury might run into it if the Pipe chanc'd to break And one being assign'd to pour in Mercury at the Top of the Tube another was plac'd to observe when the Mercury in the small Tube rose up to each of the Divisions abovemention'd and to take notice likewise how high it stood in the Long Tube at the same time where the several Observations were set down and are contain'd in the following Table A Table of the Condensation of the Air. A A B C D E 48 12 00 Added to 29 â…› makes 29 2 16 29 2 16 46 11 ½ 01 7 16 30 9 16 30 6 16 44 11 02 13 16 31 15 16 31 12 16 42 10 ½ 04 6 16 33 8 16 33 1 7 40 10 06 3 16 35 5 16 35 38 9 ½ 07 14 16 37 36 15 19 36 9 10 2 16 39 3 16 38 â…ž 34 8 ½ 12 8 16 41 10 16 41 2 17 32 8 15 1 16 44 3 16 43 11 16 30 7 ½ 17 15 16 47 1 16 46 â…— 28 7 21 3 16 50 5 16 50 26 6 ½ 25 3 16 54 5 16 53 10 13 24 6 29 11 16 58 13 16 58 2 8 22 5 ½ 34 15 16 64 1 16 63 6 11 21 5 ¼ 37 15 16 67 1 16 66 4 7 20 5 41 9 16 70 11 16 70 19 4 ¾ 45 74 2 16 73 11 19 18 4 ½ 48 12 16 77 14 16 77 â…” 17 4 ¼ 53 11 16 82 12 16 82 4 17 16 4 58 2 16 87 14 16 87 â…œ 15 3 ¾ 63 15 16 93 1 16 93 1 â— 14 3 ½ 71 5 16 100 7 16 99 6 7 13 3 ¼ 78 11 16 107 13 16 107 7 13 12 3 88 7 16 117 4 16 116 4 8 A A The Number of Equal Spaces in the Shorter Leg which contain'd the same Parcel of Air differently Expanded B The Height of the Mercury in the Long Tube by whose weight the Air in the Short one was compress'd C The Height of the Mercury which counterpois'd the weight of the Incumbent Atmospere D The Aggregate of the Columns B and C shewing what Pressure was sustain'd by the Included Air. E What that Pressure should be allowing the Pressures and Expansions to be Reciprocal Porportions But in Trying this Experiment whoever pours in the Mercury he must do it by degrees and according to the Directions of the other that takes notice of the Ascent of the Mercury below for if it be pour'd in without Caution it may rise up above the Marks plac'd on the Outsides before due Observations can be made Having by the weight of so vast a Cylinder of Mercury compress'd the Air into a Quarter of the Space it possess'd before we observ'd tho' it could not be sensibly condens'd further by Cold yet the Flame of a Candle brought near it gave us reason to think that a greater degree of Heat would have expanded it but fearing the Cracking of the Tube we durst not try it From the Experiment it appears That as the Air is more or less compress'd so it is able to counterpoise a Heavier or Lighter Cylinder of Mercury And that the Mercury was born up by the Spring of that condens'd Air appear'd by sucking up the Air out of the Tube when the Mercury was 100 Inches high in the Pipe for the Pressure of the incumbent Pillar of the Atmosphere being by that means taken off the Mercury was rais'd in the Long Tube by the Expansion of the Air in the Short Leg And not by any Funiculus since the Objector confesses that cannot raise more than a Cylinder of 30 Inches The Air 's Rarefaction consider'd But together with what hath been said it may not a little illustrate our Doctrin of the Spring of the Air to observe how much it's Spring is weaken'd accordingly as it is differently Expanded and Rarify'd A Table of the Air 's Rarefaction A B C D E 1 00 0 9 Substracted from 29 ¾ leaves 29 ¾ 29 ¾ 1 ½ 10 â… 19 â…› 19 â…š 2 15 â…œ 14 â…œ 14 â…ž 3 20 2 8 9 4 8 9 15 12 4 22 â… 7 â…› 7 7 16 5 24 â…› 5 â… 5 19 20 6 24 â…ž 4 â…ž 4 23 24 7 25 4 8 4 2 8 4 ¼ 8 26 0 0 3 0 8 3 23 32 9 26 â…œ 3 3 0 3 11 36 10 26 6 3 3 0 0 2 39 40 12 27 â…› 2 â… 2 23 48 14 27 4 8 2 2 8 2 â…› 16 27 â— 8 2 0 0 1 55 64 18 27 â…ž 1 â…ž 1 47 72 20 28 1 6 8 1 9 80 24 28 â…› 1 4 8 1 22 96 28 28 â…œ 1 â…œ 1 1 16 32 28 4 8 1 2 8 0 110 128 A The Number of Equal Spaces at the Top of the Tube which the same Parcel of Air was contain'd in B The Height of the Mercury which together with the Included Air counterpois'd the Pressure of the Atmosphere C The Pressure of the Atmosphere D The Aggregate of B to C representing the Pressure counterpois'd by the Included Air. E What that Pressure should be according to the Hypothesis In which Experiment it is to be Noted First That we made use of a Glass-Tube about 6 Foot long sealed at one End Secondly We had in Readiness a Glass-Pipe about the Diameter of a Swan's Quill which was mark'd with a Paper stuck upon it divided into Inches and half Quarters which being immers'd in the other Cylinder of Mercury and open at both Ends that the Mercury might rise in it it help'd to fill the other up And about an Inch of it's standing above the Mercury the Orifice was seal'd up so that an Inch of Air was contain'd in the Tube which by lifting up the Tube was gradually expanded to
it was to be noted That when first the Water appear'd in the Glass Tube they would be very numerous and form a Froth yet when the Pumping was further continu'd they grew less and less Secondly we observ'd that the Water made several Vibrations in it's Rise which tho' near a Foot at the first grew less and less Thirdly it may be observ'd that the Baroscope consulted before some time after was noted to have risen considerably so that had the Experiment been repeated again the Water would have been buoy'd up a good deal higher Now from this Experiment it appears how improbable it is what some Men teach concerning the Rise of Water in Spiral Pipes up to the Top of high Mountains since it is evident that it cannot be drawn higher than 36 Foot by a Sucking Pump EXPERIMENT XVIII About the Bending of a Springy Body in the Exhausted Receiver TO be satisfy'd how much the Elasticity of Bodies depends on the Influence of the Air I fix'd one End of a Whale-bone in a Trencher and ty'd a Weight to the other by which it was bent so low as almost to touch the Plane under it This being convey'd into our Receiver upon the Exhausting of the Receiver I could not perceive any Alteration EXPERIMENT XIX Concerning the making of Mercurial Gauges whereby to estimate how much the Receiver is exhausted SEveral Gauges have been made use of to discover when the Receiver is well exhausted as by suspending a Bladder which is almost empty of Air or by inverting a small Tube in which Spirit of Wine was contain'd but the former taking up too much Room in the Receiver and the latter not discovering whether the Receiver was exhausted or not till the Air contain'd was too much Rarefi'd for any Considerable Observations Therefore to enable me to make more Observations in the several Degrees of the Receiver's Exsuction I took a slender Pipe of Glass about 10 Inches long and as small as a Goose Quill and having melted it at a flame so as to soften it and make it apt to be bent I caus'd it to be put into the Form represented by Plate 5. Fig. 4. so that about an Inch of the lower Leg being fill'd with Air See Plate 5â— Fig. 4. and the rest of that as well as the greatest Part of the short one being fill'd with Quicksilver the Expansion of that Air might easily be perceiv'd by pasting a Piece of Paper upon that Tube divided into several exact Parts for as the Receiver is more or less expanded the Air in the longer Leg of the Gage will be extended to some of those Marks and if when the Air is so expanded the Experimenter desires to know at each of those Marks how much the Receiver is exhausted it will appear by letting in as much Water as the Capacity of the Receiver is able at that time to hold so that if when the Air is at any determinate Mark the Water be let in and it appears that the Air in the Receiver was so far Evacuated by observing how much Water will be admitted when the Air is expanded to each Mark the Gage for the future will not only inform us how much the Air is exhausted but by the help of the small Gage a larger may be made by putting both into an exhausted Receiver at once for by observing when the Air is expanded to each Mark in the little one how far it is expanded in the large one we may learn how much the Receiver is exhausted for the future by taking notice of the Expansion of the Air in the Leg of that larger Gage And This Gage is much more useful than some others First because the Mercury being a heavy Body the Air by expanding it self is less apt to make it run over or to make it's way in the Form of Bubbles through the Mercurial Cylinder as it would if other Fluids were made use of instead of it Secondly The longer Leg of the Gage is to be mark'd by sticking Wax or Knobs of Glass to the Pipe every Tenth being of a different Colour from the rest at equal Distances from each other which Divisions will be less subject to be rubb'd off than Papers which are also subject in some Experiments to be wet Thirdly The Leg of the Syphon in which the Air is included may be either seal'd up before it is divided by the aforemention'd Marks or after by drawing out the End of the Tube into a small Apex and when about an Inch of the Pipe is fill'd with Air it may be seal'd up by blowing a Lamp Horizontally upon the Apex Fourthly Where very Nice Observations are to be made and the Receiver admits of a longer Gage instead of Mercury we may make use of a Tincture of Roses or of Spirit of Wine with Cocheneel in which the Exsuction of the Air will be more nicely represented Fifthly We may vary the Mercurial Gage by ordering the shorter Leg so that it may have a Bubble about half an Inch Diameter at an Inch distance from the Basis of that Leg which Bubble must have a Pipe upon the upper Part of it to give way to the Air which Bubble hath this Advantage above the other that less Air may be contain'd in the Top of the longer Leg since the Mercury not being capable of being rais'd so high the Rarefaction of the included Air will be render'd more apt to be estimated by the Eye Sixthly This Gage is much more useful than those mention'd by other Authors because it gives us an Account of the several Degrees of the Air 's Rarefaction EXPERIMENT XX. An easie way to make the Pressure of the Air sensible to the Touch. The Pressure of the Air sensible to the Touch. THE Pressure of the Air will be made sensible to the Touch if a Tapering Tube of Brass whose Cavity at one end is an Inch and the other two Inches and an half wide be fix'd to the Pump instead of a Receiver for if when the larger Orifice is Cemented on the Pump one presses the Palm of ones Hand upon the smaller Orifice and the Pump be set on Work it will be a difficult Matter to take off ones Hand and not a little painful but the Pressure of the Incumbent Atmosphere will have a much more sensible Effect if the larger Orifice be upwards instead of the smaller EXPERIMENT XXI About the subsiding of Mercury in the Tube of the Torrecellian Experiment to the Level with the Superficies of the Stagnant Mercury THE lower Part of the Ball of a Bolt-head being circularly cut off we made use of it for a Receiver including a Baroscope in it and upon the first Exsuction the Mercury subsided from 29 Inches to 9 or 10 and by three Exsuctions more would be brought to a Level with the Stagnant Mercury but would rise to it's first Station again as the Air was admitted in flower or faster In which Experiment it is to be noted First
with Steel afforded Sparks of fire much bigger than those that are usually struck from Flint Whereas two cubial pieces of Load-Stone being struck together afforded Sparks but not so large as the former EXPERIMENT V. IF an oblong Load-Stone be cool'd in a perpendicular Posture the lower End becomes it's Northern Pole yet if that End instead of being expos'd to the Effluvia of the Earth be cool'd whilst resting on the Northern Pole of a strong Load-Stone it will be the Southern Pole and will attract the North End of a Needle EXPERIMENT VI. IF a Load-Stone which hath lost it's attractive Virtue be heated red hot and cool'd in a perpendicular Posture upon the North Pole of a vigorous Load-Stone and continue there for some time the attractive Virtue is renew'd EXPERIMENT VII A Load-Stone that hath lost it's attractive virtue by Ignition will not acquire so durable an attractive Virtue by being apply'd cold as hot to a Load-Stone N. B. Tho' several Load-Stones lose their attractive Virtue by Ignition yet the Observation does not hold in all since English ones not only retain a Directive but an Attractive Virtue after it EXPERIMENT VIII HAving heated two Load-Stones red hot and placed them upon a Plate of Silver we found that as they grew colder it had a more sensible Operation on them EXPERIMENT IX WE observ'd that one of the two Magnets just now mention'd not only retain'd something of it's Magnetical Qualities when twice ignited but being thrust into Filings of Steel carry'd a considerable Quantity of them up with it which shews how firmly the Qualities of some Magnets are lodg'd in it EXPERIMENT X. BUT we observ'd that the Magnet which would thus carry Filings of Steel along with it being heated again and suddenly immers'd in Water when cool would not carry Filings of Steel along with it as before nor would not move a well-pois'd Needle except held near to the Point of it EXPERIMENT XI AN oblong Load-Stone of a black Colour which weigh'd about three Drachms by being kept some time in a Charcoal Fire lost much of it's Colour and about â…š of a Grain in Weight And to discover the Affinity betwixt a Load-Stone and Iron Ore I took a Lump of it which was almost like white Stone and observ'd that it did not only manifestly move a Needle but when ignited underwent a sensible Change in Colour and would attract the North End of a Needle EXPERIMENT XII TO prove that some Bodies not usually class'd amongst Magnetical ones have nevertheless Magnetical Qualities I shall subjoyn That a Brick being divided into two oblong pieces and heated in the Fire acquir'd a Verticity by cooling North and South it 's Southward End being in some measure able to draw the North Point of a Mariner's Needle which the other End of the Brick would drive away EXPERIMENT XIII HAving without the help of Iron Instruments powder'd a black Load-Stone and pour'd Spirit of Salt upon the fine Powder it caus'd such an Ebullition as usually succeeds the Effusion of that Liquor upon Filings of Iron and likewise rais'd fetid Fumes And being kept for about two Nights in Digestion extracted a strong Tincture being almost red and not green like that of Mars yet would like that of Iron turn a Tincture of Galls black which in several Positions would appear Blew And to this I shall add that a Solution of Load-Stones being made in Aqua Regia the Tincture appear'd to be of a golden Colour EXPERIMENT XIV HAving powder'd an ignited Load-Stone and digested Spirit of Salt upon it it extracted a Tincture which was much like that of troubled Gold and would turn an Infusion of Galls black This Tincture being evaporated would not shoot into Crystals but upon an Affusion of Salt of Tartar yielded a Precipitate much resembling a Solution of Vitriol whereas another Part of it upon an Addition of Spirit of fermented Urine afforded a yellowish red Precipitate EXPERIMENT XV. HAving wet a red Mineral which I suspected to be Iron Ore with Linseed Oyl and preserv'd the Powder in a red hot Crucible for about two hours it was turn'd black and when cool had acquir'd a Magnetical Virtue which another Portion of it did tho' it was not as the other wet with that Oyl CHAP. XXV Experiments and Notes about the Mechaninal Origin and Production of Electricity Of the mechanical Production of Electricity THO' Electricity be a Quality generally reckon'd amongst the Number of those that are term'd occult ones yet there is no need to ascribe it to the power of a Substantial Form since it may be mechanically produced by material Effluviums issuing from and returning to the Electrical Body assisted in it's Operation by the External Air. There are several Modern Hypotheses which endeavour to account for Electricity as the Learned Cabeus's who supposes that the Steams of the electrical Body discussing and expelling the ambient Air that when driven off is violently oppos'd by the Atmospherical Air and being driven back upon the Body said to be attracted forces it up to the electrical Body Another Hypothesis propos'd by the Ingenious Sir Kenelm Digby and embrac'd by Dr. Brown and several others is that the Electrick Body being rubb'd emits unctuous Steams which being cool'd by the External Air shrink back and carry along with them those light Bodies which lie in their way Of this Opinion is Gassendus who supposes these unctuous Steams to cross each other and by getting into the Pores of Straws and other attracted Bodies take faster hold of them and when they shrink back draw those Bodies along with them Cartesius rejecting these Hypotheses supplants another which I cannot in few Words lay down but all the Reason he rejects them being because he supposes Glass incapable of emitting Effluvia it will be sufficient to remove that difficulty to Observe that if two Pieces of Glass be rubbed together they emit odorous and sometimes very Stinking Effluvia But without taking any further Notice of what Moderns have laid down about Electricity since they allow it to be performed by Virtue of subtle Emanations from the Attracting Body It may suffice that I proceed to mention some Phenomena that make us probably believe it done by Virtue of Mechanical Affections either of the Attracting Body or both And First it is Observed that most if not all Electrical Bodies attract not till warm'd by which heat they are enabled to send forth Eufflvia Secondly Amber attracts most vigorously when warmed by rubbing and Chafing by which Action the Motion of the Effluvia as well as of it's internal Parts are more agreeably modified than by the Action of Fire but if the Parts of the Amber be first put into Motion by the Fire and then Modifi'd by Chafing it sooner becomes Electrical Thirdly Tersion as well as Chafing promotes Electricity by removing those Bodies which might choak the Pores of the Amber and obstruct the Efflux of Emanations by sticking to the surface of it