Selected quad for the lemma: cause_n

Word A	Word B	Word C	Word D	Occurrence	Frequency Band	MI	MI Band	Prominent
cause_n	find_v	great_a	reason_n	2,541	5	4.6084	4	true

Text snippets containing the quad

ID	Title	Author	Corrected Date of Publication (TCP Date of Publication)	STC	Words	Pages
A67384	A discourse of gravity and gravitation, grounded on experimental observations, presented to the Royal Society, November 12. 1674 by John Wallis ...	Wallis, John, 1616-1703.; Royal Society (Great Britain)	1675 (1675)	Wing W574; ESTC R18644	25,475	42

as Water And from him the Torricellian Experiment takes its name The Experiment is thus administred in Fig. 36. A Glass-Pipe closed at the bottom being filled with Quick-silver and then inverted the orifice being stopped with the finger or otherwise till it be immersed in a Vessel of stagnant Quick-silver and then opened If the height of the Pipe above the stagnant Quick-silver be not more than 29 inches or thereabouts it will remain full The cause hereof say they is Ne detur Vacuum For if the Quick-silver should sink there being no way for the Air to enter there would ensue a Vacuum which nature abhors The cause say we is Because the weight of the incumbent Air on A which we have already proved to be Heavy is equivalent to the weight of 29 inches of Quick-silver Which therefore being defended by the closed Glass which we suppose otherwise to be held firm from any other Pressure than its own Weight is by that Counter-pressure sustained But further If the height of the Pipe above the stagnant Quick-silver be more than about 29 inches that in the Pipe will sink to that height as at E leaving space above it in the Glass void of Quick-silver But whether filled by any other imperceptible Fluid we dispute not The Reason why it so sinks our Ancestors have not assigned Because they were not at all aware of this Phaenomenon but thought that ne detur vacuum it would remain full whatever the height of the Tube were Some Moderns with Des Cartes that they might avoid a Vacuum do imagine that a Materia subtilis of which no Sense can make any dicovery piercing the Pores of the Glass supplies that place But if it will so supply the place above E and give the Quick-silver leave to sink so low why it might not as well come-in to relieve the rest and so give it leave to sink to A I do not find Others with Linus imagine that the weight of 29 inches of Quick-silver doth stretch some part of its upper surface into a subtile matter very thin yet so as to fill that seemingly void space but because a less weight will not serve so to stretch it it falls no lower which stretched matter like a Funiculus holds up the rest ne detur vacuum But why this Weight should stretch some very small part of it so prodigiously thin and not stretch the rest at all rather than give some moderate Tensure to the whole they do not that I remember assign any Reason Others suppose this Funiculus to be made not by stretching the upper part of the Quick-silver but by squeezing out the more subtil parts from the whole body of it which like a vapour fills that seemingly void space but that less than such a weight would not so squeeze it and therefore it falls no lower But why it should so fall out that all Liquors whatever of never so different Texture should by the same weight be thus dissolvable and not rather some require a greater some a lesser weight thus to resolve or squeeze them they assign no Reason Yet we find so it is since that the lighter the Liquor is the greater height must be allowed and in such proportion greater to make up an equivalent weight But the cause is say we and it seems the most simple and unforced account because the Counter-pressure of the Air being equivalent to that of about 29 inches so much it is able to sustain but no more and just so much weight it will sustain whatever the Liquor be whether specifically Lighter or Heavier and whether of a more Firm or a Looser texture and therefore to such a height it sinks but no lower And had the Ancients been aware of what we find That the Air hath a positive Gravity and consequently though it be but small in proportion to that of other bodies yet a great height of Air may countervail a lesser height of a Heavier Liquor like as we see that a greater height of Water will countervail a lesser height of Quick-silver They would not I presume have troubled themselves with a Fuga vacui but said roundly That the weight of the Air at its full height is equivalent to that of Water at the height of about 34 foot and of Quick-silver at about 29 inches and proportionably of other Fluids And consequently when in the Pump or Syringe D by the Embolus or Sucker is defended from the Airs Pressure but A exposed to it in Fig. 34. this Pressure on A will raise over B so much weight of Water Quick-silver or other Fluid as is equivalent to that Pressure In the same manner as if A and E were equally exposed to the Airs Pressure a quantity of Oyl poured on A would have raised a weight of Water or Quick-silver equivalent thereunto The like account we give of the Syphon The Pressure on A in Fig. 35. will raise the Fluid to the height of B if not greater than what is before described and from thence to O it falls by its own Weight Yet so that if O were higher than A the Airs Pressure at O would thrust up O to B supposing the Pipe not so big as that the Air could conveniently pass by the Liquor into the Pipe and it would fall down to A by its own Weight For now BO would less gravitate than BA while yet the Airs Pressure would be much the same on both There is yet a considerable Objection to be removed viz. That Air in a closed Vessel though of no great height pressing on A the surface of the stagnant Quick-silver Fig. 37. will sustain as high a Pillar thereof in a closed Tube suppose AE as if A were exposed to the open Air Whereas yet the Weight of AD within the Vessel defended by the Vessel from the Pressure of the incumbent Air cannot be of equal Weight as if it had the whole height of the Atmosphere But the Reason of this is from the Airs Spring which is always equivalent to the Pressure lying upon it And consequently the Spring of the Air in its ordinary constitution with us must be equivalent to the Weight of the incumbent Air. For if it were less the Air incumbent would yet press it closer if it were more the Spring would relax it self by thrusting away what presseth it Which being so the Air included with such a Spring must therefore press with as great a strength as is equivalent to such a Weight Like as in other Springs if ACB in Fig. 38. be pressed by the Weight D to such a Tensure as to bear it and then this Spring so remaining the Weight were taken away and our hand put in the place of it it would press as hard against the hand as before it did to sustain the Weight that is with a Force equal to that of the Weight it sustained And if thus bowed it were put in a Vessel in Fig. 39. it would with just the same Force press against the sides of it And just so it is in the present Case where the air so included doth press by its Spring just with the same Force as was that of the incumbent Air which gave it this Tensure It is yet the more evident because if by the Air-Pump part of this Air be pumped out and thereby the rest less compressed the Quick-silver in the Tube in Fig. 37. will sink from E to a lower Station as to F or G and so lower and lower as more and more Air is pumped out and the Spring thereby relaxed That is as the Spring grows weaker so it is less able to support the Weight And this quite destroys the Evasions but now mentioned That the seeming void space is filled by a thin Substance which can by the Weight of 29 inches of Quick-silver or 34 foot of Water but not by less be stretched to that fineness and that therefore it will sink to that height but not lower For by this last Experiment when the Air is included with its ordinary Tensure it sustains the Quick-silver at the height of 29 inches as if less than that Weight were too little to stretch the Quick-silver into that supposed fine substance But when that Air by pumping is weakned it will sink to 20 10 5 yea less than 1 inch of height as if now less than the Weight of 1 inch were enough so to stretch it as less than 29 inches would not do before Yet is no alteration all this while made in the Texture of the Quick-silver but in the Tensure of the Air onely 'T is therefore from this different Tensure or Spring of the Air not from any difference in the Quick-silver that it stands sometime at a higher sometime at a lower station And what hath been thus said of this Torricellian Experiment is easily applicable to others of like nature And it is confessed that as the notion of Fuga vacui or that of the Airs pressure doth stand or fall as to this Experiment so must it do as to the others also I content my self therefore to have shewed it in this without expatiating to other particulars FINIS