An essay of the great effects of even languid and unheeded motion whereunto is annexed An experimental discourse of some little observed causes of the insalubrity and salubrity of the air and its effects / by the Honourable Robert Boyle ...

CHAP. III. (Book 3)

Observat. II. We are too apt to think, that Fluid bodies, because of their softness, cannot have by their bare motion, especially if insensible, any sensible effect upon Solid ones; though the fluid moves and acts as an intire body.

'TIS not my purpose here to insist on the efficacy of the motion of such fluid bodies as may have their motions discovered by the eye, like streaming water; or mani∣festly perceived by the touch, as are the winds that beat upon us: since 'twere needless to give Instances of such obvious things, as the great ef∣fects of overflowing waters and vi∣olent winds; the later of which, not∣withstanding the great tenuity and

softness of the air and the Effluvia that swim in it, have been sometimes able to blow down not onely timber∣trees, but houses and steeples, and o∣ther the firmest Structures. But the motions I intend to speak of in this Chapter are such, as we do not im∣mediately either see or feel; and though these be exceeding rare, yet the operation of Sounds, even upon solid bodies, and that at a distance from the sonorous ones, afford me some Instances to my present purpose, which I shall now proceed to men∣tion.

It has been frequently observed, that, upon the discharge of Ordnance and other great Guns, not onely the sound may be distinctly heard a great way off; but that, to a good distance, the tremulous motion of the Air that produces sound, without producing any sensible wind, has been able sen∣sibly to shake, and sometimes vio∣lently to break, the glass-windows of houses and other buildings, especially when the windows stand in the way

wherein the propagation of the sound is directly made. 'Tis true, that these observations are most frequent, when the place, where the Artillery is placed, stands upon the same piece of ground with the Houses whose windows are shaken; and so it may be suspected, that the Shake is first communicated by the Cannon to the earth or floor on which they play, and is afterwards by that propagated through the intermediate parts of the ground to the foundations of the hou∣ses, and so to the windows. And I readily grant, and may elsewhere shew, that a violent impulse upon the ground may reach to a greater di∣stance than men usually imagine: But in our present Case I see no necessity of having recourse to any thing but the wave-like motion of the Air for the production of our Phaenomenon, since the like may be produced by Local Motion transmitted by Fluids, as may appear by the following In∣stances.

I was once invited by an Engineer,

to see triall made of a strange Instru∣ment he had to sink ships, though great ones, in a few minutes; and though an unlucky Accident kept me from arriving there 'till near a quarter of an hour after the triall had been made on an old fregat, with bet∣ter successe than my Philanthropy allowed me to wish; yet causing my self to be rowed to the place, where the great vessell was newly sunk, the odness of the effect, which was performed upon the water by a small Instrument outwardly applied, made me inquisitive, what noise and com∣motion had been made: And I was informed partly by the Engineer him∣self, and partly by some acquaintances of mine, who among a great number of Spectators stood aloof off in ships and other vessels lying at anchor, to see the event; that, upon the En∣gine's operating, the explosion was so great, that it made a kind of storm in the water round about, and did so rudely shake vessels that lay at no inconsiderable distance, as to make

those that stood on them to stagger.

In the late great Sea-fight between the English Fleet commanded by his Royal Highness the Duke of York, and the Dutch Admiral Opdam, (who therein lost the Victory and his Life,) though the Engagement were made very many Leagues from the Hague, yet the noise of the Guns not onely reached to that Place, but had a nota∣ble effect there; of which when I enquired of the English Embassadour that as yet resided there, he was plea∣sed to assure me, that it shook the windows of his House so violently, that not knowing what the Cause was, he was surprized and much al∣larmed, apprehending, that some rude Fellows were about to break his win∣dows to affront him. And if there be a greater disposition in some other bodies than there is in Glass-win∣dows to receive strong impulses from the Air agitated by Sounds, these may be sensibly, though not visibly, wrought upon, and that at a good distance, by the noise of a single

piece of Ordnance; as may appear by that memorable Circumstance of an odd Case about a Gangrene men∣tioned by the experienced Simon Pauli in his ingenious Tract de Febribus malignis, pag. 71. Atqui aeger ille Gallus brachio truncatus, octiduum quidem superfuit, sed horrendis totius corporis convulsionibus correptus; qui quoque, (ut & illa addam observatione dig∣nissima,) dum in Domini sui aedibus ad plateam Kiodmoggerianam, Romanè Laniorum appellares, decumberet, ac, me ac aliis aliquandiu ad Lectum illius considentibus quidem, sed nobis non at∣tendentibus, exploderentur tormenta bel∣lica ex Regiis ac Praetoriis navibus, si∣nistrâ truncum dextri brachii fovens ac complectens, toties quoties exploderen∣tur singula exclamabat, Au, au, me mi∣serum! Jesu, Maria, contundor penitús: adeò permolesta & intolerabilis illi erat Tormentorum explosio, & quidem ex loco satis longinquo, terrâ non firmâ aut contiguâ, verùm super salo aut mari Balthico, instituta. By this it appears, that the Guns, whose discharge pro∣duced

these painfull motions in the Patient, rested upon a floating body. And I remember, that an illustrious Commander of a very great Man of war, being asked by me, whether of the many wounded men, he had in his ship in a very long Sea-fight, none of them were affected by that noise of the Enemy's Cannon discharged in ships at a distance? He answered me, that some, whose bones were broken, would sadly complain of the Tor∣ment they were put into by the shake they felt at the going off of the E∣nemy's Cannon, though they were too much accustomed to the report of great Guns, to be, as 'twas a bare noise, offended by it. If after all this ti be surmized, that these motions were not conveyed by the air, but propagated by the water, (and, in some cases, some part of the shoar) from the ships, where the Guns were fired, to the Houses where the win∣dows were shaken, or the places where the wounded men lay: I an∣swer that, if this could be made pro∣bable,

it would accommodate me with very eminent Instances for the Chapter of the Propagable nature of Motion: And though it be very dif∣ficult to find such examples of shakes excited by sounds as are not liable to the mentioned objection; because the sonorous bodies here below do all either strike, or lean, upon such gross and visible bodies as the Earth and Water; yet there is one kind of Sound, that must be confessed to be propagated by the Air, as being made in it; and that is Thunder, whose noise does sometimes so vehemently affect the Air, though without pro∣ducing any sensible wind, that both others and I have observed it very sensibly to shake great and strong Houses, notwithstanding the distance of the clouds where the noises were first produced. And I remember, that, having inquired of some Sea-Captains, that in stout vessels sailed to the Indies, whether they had nor in those hot Regions observed their ships, though very much less tall then

houses, to be shaken by vehement Thunders? I perceived, that some of them had not much heeded any such thing; but a couple of others told me, they had observed it in their ships; and one of them told me, that once, when the claps of thunder were ex∣traordinary great, some of them shook his ship so rudely as to make the unwonted motions disorder his great Guns. All which I the less won∣der at, when calling to mind, what I have mention'd in the foregoing Chap∣ter and elsewhere of the power of the Celerity of motion, I consider, that there is no Celerity that we know of here below, that is near so great, as that wherewith a Sound is propagated through the air. For, whereas the diligent Mersennus ob∣serves, that a bullet shot out of a Can∣non or a Musket does not overpass two hundred and forty yards in a Se∣cond, or sixtieth part of a minute; I have more than once diligently ob∣served, that the motion of Sound pas∣ses above four hundred yards in the

same time of a Second here in England; which I therefore add, because Mer∣sennus relates, that in France he ob∣served a Sound to move in that time many yards more; which may possibly proceed from the differing consistence of the English air and the French.

The great Loudness of these sounds, and the vehement percussion that the Air receives in their formation, will probably make it be easily gran∣ted, that 'twas onely the Impetuosity of the motion of the Medium, that gave the shake to the windows and other solid bodies that I have been mentioning to have been made to tremble by the report of Cannon or Thunder: But yet I will not on this occasion conceal, that perhaps it may without absurdity be suspected, that Some of those tremulous motions of solid bodies might either depend upon, or at least be promoted by, some peculiar disposition, that Glasse (which is endued with springiness,) and some other bodies that perhaps are not quite devoid of that Quality,

may have to be moved by certain congruous Sounds (if I may so call them) more than they would by o∣thers, though perchance more loud. But though this surmize should be ad∣mitted; yet it would not render the lately-recited Instances improper for the design of this Discourse, but onely would make some of them fit to be referred to another Chapter; to which I shall advance, as soon as I shall have annexed an odd Observation of the experienced Platerus, which argues, that, where there is a peculiar Dispo∣sition, even in a firm body, it may re∣ceive considerable impressions from so languid a motion (though in likeli∣hood not peculiarly modified) of the air as is not sensible to other bodies of the same kind.

Foemina quaedam (says he)* 1.1 in subitaneum incidit mor∣bum, viribus subitò prostratis, se suf∣focari indesinenter clamitans, etsi neo stertoris nec tussis aliqua essent indicia; maximè verò de aura quadam adveni∣ente, si vel leviter aliquis adstantium se

moveret, quae illam opprimeret, conque∣rebatur, séque suffocari, si quis propiùs accederet, clamitabat: vixdum bidu∣um in ea anxietate perseverans, expi∣ravit. To which he adds: Vidi & alios aegros, de simili aura, quae eos, si quis illis appropinquaret, in suffocationis pe∣riculum induceret, conquerentes; quod semper pessimum esse signum depre∣hendi.

Notes

• * 1.1

  Plater. Observ. Lib. 1. p. 185.