« AnteriorContinuar »
Dr. Stuart says, " It was observable of all the sides showing darker than the middle. Dr. the spouts he saw, but more perceptible of the Mather's whirl was probably filled with dust, great one; that, towards the end, it began to the sides were very dark, but the vacuum appear like a hollow canal, only black in the within rendering the middle more transpaborders, but white in the middle; and though rent, he calls it a pillar of light. at first it was altogether black and opaque, It was in this more transparent part, beyet, now, one could very distinctly perceive tween b and c, that Stuart could see the spithe sea water to fly up along the middle of ral motion of the vapours, whose lines on the this canal, as smoke up a chimney." nearest and farthest side of the transparent
And Dr. Mather, describing a whirlwind, part crossing each other, represented smoke says, a thick dark small cloud arose, with a ascending in a chimney; for the quantity bepillar of light in it, of about eight or ten feet ing still too great in the line of sight through diameter, and passed along the ground in a the sides of the tube, the motion could not be tract not wider than a street, horribly tearing discovered there, and so they represented the up trees by the roots, blowing them up in the solid sides of the chimney. air like feathers, and throwing up stones of When the vapours reach in the pipe from the great weight to a considerable height in the clouds near to the earth, it is no wonder now
to those who understand electricity, that flashThese accounts, the one of water-spouts, es of lightning should descend by the spout, the other of a whirlwind, seem, in this par- as in that of Rome. ticular, to agree; what one gentleman de But you object, if water may be thus carried scribes as a tube, black in the borders, and into the clouds, why have we not salt rains! white in the middle, the other calls a black The objection is strong and reasonable, and I cloud, with a pillar of light in it; the latter know not whether I can answer it to your saexpression has only a little more of the mar- tisfaction. I never heard but of one salt rain, vellous, but the thing is the same; and it and that was where a spout passed pretty near seems not very difficult to understand. When a ship, so I suppose it to be only the drops Dr. Stuart's spouts were full charged, that is thrown off from the spout, by the centrifugal when the whirling pipe of air was filled be force (as the birds were at Hatfield) when tween a a a a and 6 b bb, Fig. I. with quan- they had been carried so high as to be above, tities of drops, and vapour torn off from the co-or to be too strongly centrifugal, for the preslumn W W Fig. II, the whole was rendered sure of the concurring winds surrounding it:
and, indeed, I believe there can be no other kind of salt rain; for it has pleased the goodness of God so to order it, that the particles of air will not attract the particles of salt, though they strongly attract water.
Hence, though all metals, even gold, may Vac.
be united with air, and rendered volatile, salt remains fixt in the fire, and no heat can force it up to any considerable height, or oblige the air to hold it. Hence, when salt rises, as it will a little way, into air with water, there is instantly a separation made; the particles of water adhere to the air, and the particles of
salt fall down again, as if repelled and forced so dark, as that it could not be seen through, off from the water by some power in the air; nor the spiral ascending motion discovered ; or, as some metals, dissolved in a proper menbut when the quantity ascending lessened, the struum, will quit the solvent when other matpipe became more transparent, and the ascend- ter approaches, and adhere to that, so the waing motion visible. For by inspection of the ter quits the salt, and embraces the air ; but figure given in this page, representing a sec- air will not embrace the salt, and quit the tion of our spout, with the vacuum in the mid- water, otherwise our rains would indeed be dle, it is plain that if we look at such a hollow salt, and every tree and plant on the face of pipe in the direction of the arrows, and sup- the earth be destroyed, with all the animals pose opaque particles to be equally mixed in that depend on them for subsistence-He the space between the two circular lines, who hath proportioned and given proper quaboth the part between the arrows a and b, and lities to all things, was not unmindful of this. that between the arrows c and d, will appear Let us adore Him with praise and thanksgivmuch darker than that between b and c, as ing. there must be many more of those opaque par By some accounts of seamen, it seems the ticles in the line of vision across the sides, column of water W W, sometimes falls sudthan across the middle. It is thus that a hair denly; and if it be, as some say, fifteen or ina microscope evidently appears to be a pipe, twenty yards diameter, it must fall with great
force, and they may well fear for their ships. I had often seen water-spouts at a distance, By one account, in the Transactions, of a and heard many strange stories of them, but spout that fell at Colne, in Lancashire, one never knew any thing satisfactory of their nawould think the column is sometimes lifted ture or cause, until that which I saw at Anoff from the water, and carried over land, and tigua; which convinced me that a waterthere let fall in a body; but this, I suppose, spout is a whirlwind, which becomes visible happens rarely.
in all its dimensions by the water it carries up Stuart describes his spouts as appearing no with it. bigger than a mast, and sometimes less; but There appeared not far from the mouth of the they were seen at a league and a half dis- harbour of St. John's, two or three water-spouts,
one of which took its course up the harbour. Its I think I formerly read in Dampier, or some progressive motion was slow and unequal, not other voyager, that a spout, in its progressive in a strait line, but, as it were, by jerks or motion, went over a ship becalmed, on the starts. When just by the wharf, I stood about coast of Guinea, and first threw her down on one hundred yards from it. There appeared one side, carrying away her foremast, then in the water a circle of about twenty yards suddenly whipped her up, and threw her diameter, which, to me, had a dreadful, though down on the other side, carrying away her pleasing appearance. The water in this cir mizen-mast, and the whole was over in an in- cle was, vigently agitated, being whieked. stant. I suppose the first mischief was done about, and carried up into the air with great by the fore-side of the whirl, the latter by the rapidne and noise, and reflected a lustre, as hinder-side, their motion being contrary.
if the slined bright on that spot, which I suppose a whirlwind, or spout, may be was more conspicuous, as there appeared a stationary, when the concurring winds are dark circle around it. When it made the equal; but if unequal, the whirl acquires a shore, it carried up with the same violence progressive motion, in the direction of the shingtis, staves,* large picces of the roofs of strongest pressure.
houses,&. and one small wooden house it When the wind that gives the progressive lifted entity from the foundation on which it motion becomes stronger below than above, stood, had carried it to the distance of fouror above than below, the spout will be bent, teen fertigwhere it settled without breaking and, the cause ceasing, straiten again.
setting; and, what is remarkable, Your queries, towards the end of your pa- thoug, the whirlwind moved from west to per, appear judicious, and worth considering. east, t.se house moved from east to west.At present am not furnished with facts suffi- Two or three negroes and a white woman, cient to make any pertinent answer to them; were killed by the fall of timber, which it carand this paper has already a sufficient quan
into the air and dropped again. After tity of conjecture.
passing through the town, I believe it was Your manner of accommodating the ac- soon dissipated ; for, except tearing a large counts to your hypothesis of descending spouts limb from a tree, and part of the cover of a is, I own, ingenious, and perhaps that hypo- sugar work near the town, I do not remember thesis may be true. I will consider it farther, any further damage done by it. I conclude, but, as yet, I am not satisfied with it, though wishing you success in your inquiry. hereafter I may be.
W. MERCER. Here you have my method of accounting for the principal phenomena, which I submit to your candid examination.
Dr. Perkins to Dr. Franklin. I now seem to have almost written a book, instead of a letter, you will think it Shooting Stars.—Read at the Royal Society,
July 8, 1756.
Boston, May 14, 1753.
I RECEIVED your letter of April last, and
make me at a loss which side the truth lies Dr. Mercer to Dr. Franklin.
on, and determine me to wait for farther evi. Description of a Water-spout at Antigua.—Read dence. at the Royal Society, June 24, 1756.
As to shooting-stars, as they are called, I New-BRUNSWICK, November 11, 1732. know very little, and hardly know what to I Am favoured with your letter of the 2d in- say. 'I imagine them to be passes of electric stant, and shall
, with pleasure, comply with fire from place to place in the atmosphere, your request, in describing (as well as my perhaps occasioned by accidental pressures of memory serves me) the water-spout I saw at a non-electric circumambient fluid, and so by Antigua; and shall think this, or any other
" service I can do, well repaid, if it contributes might belying in quantities on the wharf
, for sale, as
* I suppose shingles, staves, timber, and other lumber to your satisfaction in so curious a disquisition. I brought from the northern colonies. --B. F.
propulsion, or elicited by the circumstance of Indies, had one come across the stern of his a distant quantity minus electrified, which it vessel, and passed away from him. The washoots to supply, and becomes apparent by its ter came down in such quantity that the precontracted passage through a non-electric me- sent capt. Melling, who was then a common dium. Electric fire in our globe is always in sailor at the helm, says it almost drowned him, action, sometimes ascending, descending, or running into his mouth, nose, ears, &c. and passing from region to region. I suppose it adds, that it tasted perfectly fresh. avoids too dry air, and therefore we never One passed by the side of captain Howsee these shoots ascend. It always has free- land's ship, so near that it appeared pretty dom enough to pass down unobserved, but, I plain that the water descended from first to imagine, not always so, to pass to distant last. climes and meridians less stored with it. Mr. Robert Spring was so near one in the
The shoots are sometimes all one way, Straits of Malacca, that he could perceive it to which, in the last case, they should be. be a small very thick rain.
Possibly there may be collections of parti All these assure me, that there was no cles in our atmosphere, which gradually wind drawing towards them, nor have I found form, by attraction, either similar ones per se, any others that have observed such a wind. or dissimilar particles, by the intervention of It seems plain, by these few instances, that others. But then, whether they shoot or ex- whirlwinds do not always attend spouts; and plode of themselves, or by the apphich of that the water really descends in some of some suitable foreign collection acciyentally them. But the following consideration, in brought near by the usual commotions and confirmation of this opinion, may, perhaps, interchanges of our atmosphere, especially render it probable that all the spouts are dewhen the higher and lower regions intermix, scents. before change of winds and weather, jeleave. It seems unlikely that there should be two
I believe I have now said enough of what sorts of spouts, one ascending and the other I know nothing about. If it shouldhurve for descending. your amusement, or any way obloge you, it is It has not yet been proved that any one all I aim at, and shall, at your doširti be al- spout ever ascended. , A specious appearance ways ready to say what I think, as, wiam sure is all that can be produced in favour of this; of your candour.
and those who have been most positive about TE
it, were at more than a league's distance
when they observed, as Stuart and others, if Dr. Perkins to Dr. Franklin.:
I am not mistaken. However, I believe it
impossible to be certain whether water asWater-spouts and Whirlwinds.-Real at the cends or descend at half the distance. Royal Society, July 8, 1756.
It may not be amiss to consider the places Sports have been generally believed as- where they happen most. These are such as cents of water from below, to the region of are liable to calms from departing winds on the clouds, and whirlwinds, the means of con- both sides, as on the borders of the equinoctial veyance. The world has been very well sa- trade winds, calms on the coast of Guinea, in tisfied with these opinions, and prejudiced the Straits of Malacca, &c. places where the with respect to any observations about them. under region of the atmosphere is drawn off Men of learning and capacity have had many horizontally. I think they do not come opportunities in passing those regions where where the calms are without departing winds ; these phenomena were most frequent, but and I take the reason to be, that such place seem industriously to have declined any no- and places where winds blow towards one tice of them, unless to escape danger, as a another, are liable to whirlwinds, or other asmatter of mere impertinence in a case so clear cents of the lower region, which I suppose and certain as their nature and manner of ope- contrary to spouts. But the former are liable ration are taken to be. Hence it is has been to descents, which I take to be necessary to very difficult to get any tolerable accounts of their production. Agreeable to this, it seems them. None but those they fell near can in- reasonable to believe, that any Mediterranean form us any thing to be depended on; three sea should be more subject to spouts than or four such instances follow, where the ves others. The sea usually so called is so. The sels were so near, that their crews could not Straits of Malacca is. Some large gulphs avoid knowing something remarkable with may probably be so, in suitable latitudes; so respect to the matters in question.
the Red Sea, &c. and all for this reason, that Captain John Wakefield, junior, passing the heated lands on each side draw off the the Straits of Gibraltar, had one fall by the under region of the air, and make the upper side of his ship; it came down of a sudden, descend, whence sudden and wonderful conas they think, and all agree the descullit was densations may take place, and make these certain.
descents. Captain Langstaff, on a voyage to the West It seems to me, that the manner of their ap
pearance and procedure, favour the notion of a suppose is vulgarly called the breaking of the descent.
spout) and in the interval, between this peMore or less of a cloud, as I am imformed, riod and that of the next set of particles being always appears over the place first; then a ready to unite, the spout shuts up. So that spattering on the surface of the water below; if this reasoning is just, these phenomena agree and when this is advanced to a considerable with my hypothesis. degree, the spout emerges from the cloud, and The usual temper of the air, at the time of descends, and that, if the causes are sufficient, their appearance, if I have a right information, down to the places of spattering, with a roar- is for me too; it being then pretty cool for ing in proportion to the quantity of the dis- the season and climate; and this is worth recharge; then it abates, or stops, sometimes mark, because cool air is weighty, and will more gradually, sometimes more suddenly. not ascend; besides, when the air grows cool,
1 must observe a few things on these 'par- it shows that the upper region descends, and ticulars, to show how I think they agree with conveys this temper down; and when the my hypothesis.
tempers are equal, no whirlwind can take The preceding cloud over the place shows place. But spouts have been known, when condensation, and, consequently, tendency the lower region has been really cold. Gordownwards, which therefore must naturally don's spout in the Downs is an instance of prevent any ascent. Besides that, so far as this—(vide Philosophical Transactions) I can learn, a whirlwind never comes under where the upper region was probably not at à cloud, but in a clear sky.
all cooler, if so cold as the lower : it was a The spattering may be easily conceived cold day in the month of March, hail followed, to be caused by a stream of drops, falling but not snow, and it is observable, that not so with great force on the place, imagining the much as hail follows or accompanies them in spout to begin so, when a sudden and great moderate seasons or climes, when and where condensation happens in a contracted space, they are most frequent. However, it is not as the Ox-Eye on the coast of Guinea. improbable, that just about the place of de
The spout appearing to descend from the scent may be cooler than the neighbouring cloud seems to be, by the stream of nearly parts, and so favour the wonderful celerity of contiguous drops bringing the air into consent, condensation. But, after all, should we allow so as to carry down a quantity of the vapour the under region to be ever so much the hotof the cloud; and the pointed appearance it test, and a whirlwind to take place in it: supmakes may be from the descending course be- pose then the sea-water to ascend, it would ing swiftest in the middle, or centre of the certainly cool the spout, and then, query, whespout: this naturally drawing the outer parts ther it would not very much, if not wholly, inward, and the centre to a point; and that will obstruct its progress. appear foremost that moves swiftest. The It commonly rains when spouts disappear, phenomenon of retiring and advancing, I if it did not before, which it frequently does think may be accounted for, by supposing the not
, by the best accounts I have had; but the progressive motion to exceed or not equal the cloud increases much faster after they disapconsumption of the vapour by condensation. pear, and it soon rains. The first shows the Or more plainly thus: the descending vapour spout to be a contracted rain, instead of the which forms the apparent spout, if it be slow diffused one that follows; and the latter that in its progress downwards, is condensed as the cloud was not formed by ascending water, fast as it advances, and so appears at a stand; for then it would have ceased growing when when it is condensed faster than it advances, the spout vanished. it appears to retire; and vice versa.
However, it seems that spouts have someIts duration, and manner of ending, are as times appeared after it began to rain ; but this the causes, and may vary by several accidents. is one way a proof of my hypothesis, viz. as
The cloud itself may be so circumstanced whirlwinds do not come under a cloud. as to stop it; as when, extending wide, it I forgot to mention, that the increase of weighs down at a distance round about, while cloud, while the spout subsists, is no argument a small circle at the spout being exonerated of an ascent of water, by the spout. Since by the discharge, ascends and shuts up the thunder-clouds sometimes increase greatly passage. A new determination of wind may, while it rains very hard. perhaps, stop it too. Places liable to these Divers effects of spouts seem not so well appearances are very liable to frequent and accounted for any other way as by descent. sudden alterations of it.
The bush round the feet of them seems to Such accidents as a clap of thunder, firing be a great spray of water made by the violence cannon, &c. may stop them, and the reason of descent, like that in great falls of water may be, that any shock of this kind may oc- from high precipices. casion the particles that are near cohering, The great roar, like some vast inland falls, immediately to do so; and then the whole, is so different from the roar of whirlwinds, by thus condensed falls at once (which is what I all accounts, as to be no ways compatible.
The throwing things from it with great | be said to do so (i. e.) to fall, because all the force, instead of carrying them up into the air, lower rarefied air is ascended, whence the is another difference.
whirlwind must cease, and its burden drop; There seems some probabilty that the sail- I cannot agree to this, unless the air be obors' traditionary belief, that spouts may break served on a sudden to have grown much in their decks, and so destroy vessels, might colder, which I cannot learn has been the case. originate from some facts of that sort in for. Or should it be supposed that the spout was, mer times. This danger is apparent on my on a sudden, obstructed at the top, and this hypothesis, but it seems not so on the other : the cause of the fall, however plausible this and my reason for it is, that the whole column might appear, yet no more water would fall of a spout from the sea to the clouds cannot, than what was at the same time contained in in a natural way, even upon the largest sup the column, which is often, by many and satisposition, support more than about three feet factory accounts to me, again far from being water, and from truly supposable causes, not the case. above one foot, as may appear more plainly We are, I think, sufficiently assured, that by and bye. Supposing now the largest of not only tons, but scores or hundreds of tons these quantities to rise, it must be disseminated :descend in one spout. Scores of tons more into drops, from the surface of the sea to the than can be contained in the trunk of it, should region of the clouds, or higher; for this rea we suppose water to ascend. son it is quite unlikely to be collected into But, after all, it does not appear that the masses, or a body, upon its falling; but would above-mentioned different degrees of heat and descend in progression according to the seve-cold concur in any region where spouts usural degrees of altitude the different portions ally happen, nor, indeed, in any other. had arrived at when it received this new determination.
Now that there cannot more rise upon the Observations on the Meteorological Paper ; common hypothesis than I have mentioned,
by a Gentleman in Connecticut.—Read at may appear probable, if we attend to the only
the Royal Society, Nov. 4, 1756. efficient cause in supposed ascending spouts, “ Air and water mutually attract each other, viz. whirlwinds.
(saith Mr. F.) hence water will dissolve in We know, that the rarefaction of the lower, air, as salt in water.” I think that he hath and the condensation of the upper region of demonstrated, that the supporting of salt in air, are the only natural causes of whirlwinds. water is not owing to its superfices being inLet us then suppose the former as hot as their creased, because “ the specific gravity of salt greatest summer heat in England, and the is not altered by dividing of it, any more than latter as cold as the extent of their winter. that of lead, sixteen bullets of which, of an These extremes have been found there to alter ounce each, weigh as much in water as one the weight of the air one tenth, which is equal of a pound.” But yet, when this came to be to a little more than three feet water. Were applied to the supporting of water in air, I this case possible, and a whirlwind take place found an objection rising in my mind. in it, it might act with a force equal to the In the first place, I have always been loth mentioned difference. But as this is the to seek for any new hypothesis, or particular whole strength, so much water could not rise; law of nature, to account for any thing that therefore to allow it due motion upwards, we may be accounted for from the known genemust abate, at least, one fourth part, perhaps. ral, and universal law of nature ; it being an more, to give it such a swift ascension as argument of the infinite wisdom of the Author some think usual. But here several difficul. of the world, to effect so many things by one ties occur, at least they are so to me. As, general law. Now I had thought that the whether this quantity would render the spout rising and support of water, in air, might be opaque ? since it is plain that in drops it could accounted for from the general law of gravitanot do so. How, or by what means it may be tion, by only supposing the spaces occupied reduced small enough? or, if the water be not by the same quantity of water increased. reduced into vapour, what will suspend it in And, with respect to the lead, I queried the region of the clouds when exonerated thus in my own mind : whether if the superthere ; and, if vapourized while ascending, fices of a bullet of lead should be increased how can it be dangerous by what they call the four or five fold by an internal vacuity, it breaking ? For it is difficult to conceive how would weigh the same in water as before. I a condensatize power should instantaneously mean, if a pound of lead should be formed intake place of a rarefying and disseminating to a hollow globe, empty within, whose super
fices should be four or five times as big as The sudden fall of the spout, or rather, that of the same lead when a solid lump, it the sudden ceasing of it, I accounted for, in would weigh as much in water as before. I my way, before. But it seems necessary to supposed it would not. If this concavity mention something I then forgot. Should it I was filled with water, perhaps it might; if