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freeze as the earth, rather moderate than in Perkins of Boston to Dr. Franklin. crease the coldness of our winter winds.
The air over the sea being warmer, and On Water-Spouts.- Read at the Royal Society, therefore lighter in winter than the air over
June 3, 1756. the frozen land, may be another cause of our
BOSTON, October 16, 1752. general N. W. winds, which blow off to sea at right angles from our North-American I FIND by a word or two in your last,* that coast. The warm light sea air rising, the you are willing to be found fault with; which heavy cold land air pressing into its place. authorizes me to let you know what I am at a
Heavy fluids descending, frequently form loss about in your papers, which is only in the eddies, or whirlpools, as is seen in a funnel, article of the water-spout. I am in doubt where the water acquires a circular motion, whether water in bulk, or even broken into receding every way from a centre, and leav- drops, ever ascends into the region of the ing a vacancy in the middle, greatest above, clouds per vorticem ; i. e. whether there be, and lessening downwards, like a speaking in reality, what I call a direct water-spout. trumpet, its big end upwards.
I make no doubt of direct and inverted whirlAir descending, or ascending, may form the winds; your description of them, and the reasame kind of eddies, or whirlings, the parts of son of the thing, are sufficient. I am sensible air acquiring a circular motion, and receding too, that they are very strong, and often move from the middle of the circle by a centrifu- considerable weights. But I have not met gal force, and leaving there a vacancy; if de- with any historical accounts that seem exact scending, greatest above, and lessening down- enough to remove my scruples concerning the wards; if ascending, greatest below, and les- ascent above said. sening upwards; like a speaking trumpet, Descending spouts (as I take them to be) standing its big end on the ground, are many times seen, as I take it, in the calıns,
When the air descends with a violence in between the sea and land trade-winds on the some places, it may rise with equal violence coast of Africa. These contrary winds, or in others, and form both kinds of whirlwinds diverging, I can conceive may occasion them,
The air in its whirling motion receding as it were by suction, making a breach in a every way from the centre or axis of the large cloud. But I imagine they have, at trumpet leaves there a vacuum, which can the same time, a tendency to hinder any dinot be filled through the sides, the whirling rect or rising spout, by carrying off the lower air, as an arch, preventing ; it must then press part of the atmosphere as fast as it begins to in at the open ends.
rarefy; and yet spouts are frequent here, which The greatest pressure inwards must be at strengthens my opinion, that all of them dethe lower end, the greatest weight of the sur
scend. rounding atmosphere being there. The air
But however this be, I cannot conceive a entering rises within, and carries up dust, force producible by the rarefication and conleaves, and even heavier bodies that happen in densation of our atmosphere, in the circumits way, as the eddy, or whirl, passes over land. stances of our globe, capable of carrying wa
If it passes over water, the weight of the ter, in large portions, into the region of the surrounding atmosphere forces up the water clouds. Supposing it to be raised, it would into the vacuity, part of which, by degrees, be too heavy to continue the ascent beyond joins with the whirling air, and adding weight a considerable height, unless parted into and receiving accelerated motion, recedes small drops ; and even then, by its centrifugal still farther from the centre or axis of the force, from the manner of conveyance, it trump, as the pressure lessens; and at last, would be flung out of the circle, and fall as the trump widens, is broken into small par- scattered, like rain. ticles, and so united with air as to be support
But I need not expatiate on these matters ed by it, and become black clouds at the top and, as truth is my pursuit, shall be glad to
to you. I have mentioned my objections, of the trump
Thus these eddies may be whirlwinds at be informed. I have seen few accounts of land, water-spouts at sea. A body of water these whirl or eddy winds, and as little of the so raised, may be suddenly let fall, when the spouts; and these, especially, lame and poor motion, &c. has not strength to support it, or things to obtain any certainty by. If you the whirling arch is broken so as to admit the know any thing determinate that has been air: falling in the sea, it is harmless, unless observed, I shall hope to hear from you; as ships happen under it; but if in the progres- also of any mistake in my thoughts. “I have sive motion of the whirl it has moved from the nothing to object to any other part of your sea, over the land, and then breaks, sudden, violent, and mischievous torrents are the con.
* A Letter on Inoculation, which is transferred to a
subsequent part of this volume, that the papers on mesequences.
teorological subjects may not be interrupted.
suppositions: and as to that of the trade On the place of this spattering, arises the winds, I believe nobody can.
appearance of a bush, into the centre of which P. S. The figures in the Philosophical the spout comes down. This bush I take to Transactions show, by several circumstances, be formed by a spray, made by the force of that they all descended, though the relators these drops, which being uncommonly large seemed to think they took up water.* and descending with unusual force by a
stream of wind descending from the cloud
with them, increases the height of the spray: Dr. Perkins to Dr. Franklin.-Read at the which wind being repulsed by the surface of Royal Society, June 24, 1756.
the waters rebounds and spreads; by the first Boston, October 23, 1752.
rising the spray higher than it otherwise In the enclosed, you have all I have to say would go; and by the last making the top of of that matter. It proved longer than I ex- the bush appear to bend outwards (i. e.) the pected, so that I was forced to add a cover to cloud of spray is forced off from the trunk of ite I confess it looks like a dispute ; but that the spout, and falls backward. is quite contrary to my intentions. The sin
The bush does the same where there is no cerity of friendship and esteem were my appearance of a spout reaching it; and is de motives; nor do I doubt your scrupling the pressed in the middle, where the spout is ex. goodness of the intention. However, I must pected. This, I imagine, to be from numerconfess, I cannot tell exactly how far I was ac- ous drops of the spout falling into it, together tuated by hopes of better information, in dis- with the wind I mentioned, by their descent, covering the whole foundation of my opinion, which beat back the rising spray in the centre. which, indeed, is but an opinion, as I am This circumstance, of the bush bending very much at a loss about the validity of the outwards at the top, seems not to agree with
I have not been able to differ from what I call a direct whirlwind, but consistent you in sentiment concerning any thing else with the reversed; for a direct one would in your Suppositions. In the present case I
the bush inwards; if, in that case, any lie open to conviction, and shall be the gainer thing of a bush would appear. when informed. If I am right, you will know The pillar of water, as they call it, from its that, without my adding any more. Too much likeness, I suppose to be only the end of the said on a merely speculative matter, is but a spout immersed in the bush, a little blackrobbery committed on practical knowledge. ened by the additional cloud, and perhaps, apPerhaps I am too much pleased with these pears to the eye beyond its real bigness, by a dry notions: however, by this you will see refraction in the bush, and which refraction that I think it unreasonable to give you more may be the cause of the appearance of se trouble about them, than your leisure and in- paration, betwixt the part in the bush, and clination may prompt you to.--I am, &c. that above it. The part in the bush is cy
Since my last I considered, that, as I had lindrical, as it is above (i. e.) the bigness begun with reason of my dissatisfaction about the same from the top of the bush to the wathe ascent of water in spouts, you would not ter. Instead of this shape, in case of a whirlbe unwilling to hear the whole I have to say, wind, it must have been pyramidical. and then you will know what I rely upon. Another thing remarkable, is, the curve in
What occasioned my thinking all spouts some of them: this is easy to conceive, in descend, is that I found some did certainly do case of descending parcels of drops through
A difficulty appeared concerning the as- various winds, at least till the cloud condenses cent of so heavy a body as water, by any force so fast as to come down, as it were, uno rivo. I was apprized of as probably sufficient. And, But it is harder to me to conceive it in the above all, a view of Mr. Stuart's portraits of ascent of water, that it should be conveyed spouts, in the Philosophical Transactions. along, secure of not leaking or often dropping
Some observations on these last will in- through the under side, in the prone part: clude the chief part of my difficulties. and, should the water be conveyed so swiftly,
Mr. Stuart has given us the figures of a and with such force, up into the cloud, as to number observed by him in the Mediterra- prevent this, it would, by a natural disposition nean ; all with some particulars which make to move on in a present direction, presently for my opinion, if well drawn.
straiten the curve, raising the shoulder very The great spattering, which relators men- swiftly, till lost in the cloud. tion in the water where the spout descends, Over every one of Stuart's figures, I see a and which appears in all his draughts, I con- cloud : I suppose his clouds were first, and ceive to be occasioned by drops descending then the spout; I do not know whether it be very thick and large into the place.
so with all spouts, but suppose it is. Now, if
whirlwinds carried up the water, I should ex* Two engraved representations of water-spouts, from pect them in fair weather, but not under & the Philosophical Transactions, are given in this edi: cloud; as is observable of whirlwinds; they tion, the better to illustrate the plate on the same subject, by Dr. Franklin.
come in fair weather, not under the shade of
a cloud, nor in the night: since shade cools and so might be called air-spouts, if they were the air: but, on the contrary, violent winds objects of sight? often descend from the clouds; strong gusts I overlooked, in its proper place, Stuart's which occupy small spaces: and from the No. 11, which is curious for its inequalities, higher regions, extensive hurricanes, &c. and, in particular, the approach to breaking,
Another thing is the appearance of the which, if it would not be too tedious, I would spout coming from the cloud. This I cannot have observed a little upon, in my own way, account for on the notion of a direct spout, as, I think, this would argue against the asbut in the real descending one, it is easy. I cent, &c. but I must pass it, not only for take it, that the cloud begins first of all to the reason mentioned, but want of room bepour out drops at that particular spot, or fora- sides. men; and, when that current of drops in As to Mr. Stuart's ocular demonstration of creases, so as to force down wind and vapour, the ascent in his great perpendicular spout, the spout becomes so far as that goes opaque. the only one it appears in, I say, as to this, I take it, that no clouds drop spouts, but such what I have written supposes him mistaken, as make very fast, and happen to condense in which, yet, I am far from asserting. a particular spot, which perhaps is coldest, The force of an airy vortex, having less and gives a determination downwards, so as influence on the solid drops of water, than on to make a passage through the subjacent at the interspersed cloudy vapours, makes the mosphere.
last whirl round swifter, though it descend If spouts ascend, it is to carry up the warm slower: and this might easily deceive, withrarefied air below, to let down all and any out great care, the most unprejudiced person. that is colder above; and, if so, they must carry it through the cloud they go into (for
To Dr. Perkins. that is cold and dense, I imagine)
perhaps far into the higher region, making a wonderful Water-spouts and Whirlwinds compared.-Read appearance at a convenient distance to observe at the Royal Society, June 24, 1753. it, by the swift rise of a body of vapour, above
PHILADELPHIA, Feb. 4, 1753. the region of the clouds. But as this has never I OUGHT to have written to you, long since, been observed in any age, if it be supposable in answer to yours of October 16, concerning that is all.
the water-spout; but business partly, and I cannot learn by mariners, that any wind partly a desire of procuring further informablows towards a spout more than any other tion by inquiry among my seafaring acquaintway; but it blows towards a whirlwind, for a ance, induced me to postpone writing, from large distance round.
time to time, till I am now almost ashamed to I suppose there has been no instance of the resume the subject, not knowing but you may water of a spout being salt, when coming have forgot what has been said upon it. across any vessel at sea. I suppose too, that Nothing certainly, can be more improving there have been no salt rains; these would to a searcher into nature, than objections jumake the case clear.
diciously made to his opinion, taken up, perI suppose it is from some unhappy effects haps, too hastily: for such objections oblige of these dangerous creatures of nature, that him to re-study the point, consider every cirsailors have an universal dread on them, of cumstance carefully, compare facts, make exbreaking in their deck, should they come periments, weigh arguments, and be slow in across them.
drawing conclusions. And hence a sure adI imagine spouts, in cold seasons, as Gor- vantage results; for he either confirms a don's in the Downs, prove the descent. truth, before too slightly supported; or disco
Query. Whether there is not always vers an error, and receives instruction from more or less cloud, first, where a spout ap the objector. pears ?
In this view I consider the objections and Whether they are not, generally, on the remarks you sent me, and thank you for them borders of trade-winds; and whether this is sincerely: but, how much soever my inclinafor, or against me?
tions lead me to philosophical inquiries, I am Whether there be any credible account so engaged in business, public and private, of a whirlwind's carrying up all the water in that those more pleasing pursuits are frequenta pool, or small pond: as when shoal, and the ly interrupted, and the chain of thought nebạnks low, a strong gust might be supposed to cessary to be closely continued in such disblow it all out?
quisitions, is so broken and disjointed, that it Whether a violent tornado, of a small ex. is with difficulty I satisfy myself in any
of tent, and other sudden and strong gusts, be them: and I am now not much nearer a connot winds from above, descending nearly per- clusion, in this matter of the spout, than when pendicular; and, whether many that are call. I first read your letter. ed whirlwinds at sea, are any other than these, Yet, hoping we may, in time, sift out the
truth between us, I will send you my presents that happened in cold weather, in the Downs, thoughts, with some observations on your described by Mr. Gordon in the Transactions, reasons on the accounts in the Transactions, was, for that reason, thought extraordinary ; and on other relations I have met with but he remarks withal, that the weather, Perhaps, while I am writing, some new light though cold when the spout appeared, was may strike me, for I shall now be obliged to soon after much colder: as we find it, comconsider the subject with a little more atten- monly, less warm after a whirlwind. tion.
You agree, that the wind blows every way I agree with you, that, by means of a ya- towards a whirlwind, from a large space cuum in a whirlwind, water cannot be sup- round. An intelligent whale-man of Nanposed to rise in large masses to the region of tucket, informed me that three of their vesthe clouds; for the pressure of the surround-sels, which were out in search of whales, ing atmosphere could not force it up in a con- happening to be becalmed, lay in sight of tinued body, or column, to a much greater each other, at about a league distance, if I height, than thirty feet. But if their really remember right, nearly forming a triangle : is a vacuum in the centre, or near the axis of after some time, a water-spout appeared near whirlwinds, then, I think, water may rise in the middle of the triangle, when a brisk breeze such vacuum to that height, or to a less height, of wind. sprung up, and every vessel made as the vacuum may be less perfect.
sail; and then it appeared to them all, by the I had not read Stuart's account, in the setting of the sails, and the course each vessel Transactions, for many years, before the re-stood, that the spout was to the leeward of ceipt of your letter, and had quite forgot it; every one of them; and they all declared it but now, on viewing his draughts, and consi- to have been so, when they happened afterdering his descriptions, I think they seem to wards in company, and came to confer about favour my hypothesis ; for he describes and it. So that in this particular likewise, whirldraws columns of water, of various heights, winds and water-spouts agree. terminating abruptly at the top, exactly as But, if that which appears a water-spout at water would do, when forced up by the pres- sea, does sometimes, in its progressive motion, sure of the atmosphere into an exhausted tube. meet with and pass over land, and there pro
I must, however, no longer call it my hy duce all the phenomena and effects of a whirlpothesis, since I find Stuart had the same wind, it should thence seem still more evident, thought, though somewhat obscurely express that a whirlwind and a spout are the same. ed, where he says, “he imagines this phe I send you, herewith, a letter from an ingenomenon may be solved by suction (impro- nious physician of my acquaintance, which perly so called) or rather pulsion, as in the gives one instance of this, that fell within his application of a cupping glass to the flesh, observation. the air being first voided by the kindled flax." A fluid, moving from all points horizontally,
In my paper, I supposed a whirlwind and towards a centre, must, at that centre, either a spout to be the same thing, and to proceed ascend or descend. Water being in a tub, if from the same cause; the only difference be a hole be opened in the middle of the bottom, tween them being, that the one passes over will flow from all sides to the centre, and there land, the other over water. I find, also, in descend in a whirl. But, air flowing on and the Transactions, that M. de la Pryme was near the surface of land or water, from all of the same opinion; for he there describes sides, towards a centre, must at that centre two spouts, as he calls them, which were seen ascend; the land or water hindering its deat different times, at Hatfield, in Yorkshire, scent. whose appearances in the air were the same If these concentring currents of air be in with those of the spouts at sea, and effects the the upper region, they may, indeed, descend same with those of real whirlwinds. in the spout or whirlwind; but then, when
Whirlwinds have generally a progressive, the united current reached the earth or waas well as a circular motion ; so had what is ter, it would spread, and, probably, blow evecalled the spout, at Topsham, as described in ry way from the centre. There may be the Philosophical Transactions, which also whirlwinds of both kinds, but from the comappears, by its effects described, to have been monly observed effects, I suspect the rising a real whirlwind. Water-spouts have, also, one to be the most common : when the upper a progressive motion; this is sometimes air descends, it is, perhaps, in a greater body, greater, and sometimes less ; in soune violent, extending wider, as in our thunder-gusts, and in others barely perceivable. The whirlwind without much whirling; and, when air deat Warrington continued long in Acrement- scends in a spout, or whirlwind, I should raClose.
ther expect it would press the roof of a house Whirlwinds generally arise after calms | inwards, or force in the tiles, shingles, or and great heats: the same is observed of thatch, force a boat down into the water, or a water-spouts, which are, therefore, most fre- piece of timber into the earth, than that it quent in the warm latitudes. The spout I would lift them up, and carry them away.
It has so happened, that I have not met with I'would only first beg to be allowed two or any accounts of spouts, that certainly descend- three positions, mentioned in my former paed; I suspect they are not frequent. Please per. to communicate those you mention. The ap. 1. That the lower region of air is often more parent dropping of a pipe from the clouds to-heated, and so more rarefied, than the upper; wards the earth or sea, I will endeavour to consequently, specifically lighter. The coldexplain hereafter.
ness of the upper region is manifested by the The augmentation of the cloud, which, as I hail which sometimes falls from it in a hot day. am informed, is generally, if not always the 2. That heated air may be very moist, and case, during a spout, seems to show an ascent, yet the moisture so equally diffused and rarerather than a descent of the matter of which fied, as not to be visible, till colder air mixes such cloud is composed; for a descending spout, with it, when it condenses, and becomes visione would expect, should diminish a cloud. I ble. Thus our breath, invisible in summer, own, however, that cold air descending, may, becomes visible in winter. by condensing the vapours in a lower region, Now let us suppose a tract of land, or sea, form and increase clouds; which, I think, is of perhaps sixty miles square, unscreened by generally the case in our common thunder- clouds, and unfanned by winds, during great gusts, and, therefore, do not lay great stress part of a summer's day, or, it may be, for seveon this argument.
ral days successively, till it is violently heated, Whirlwinds and spouts, are not always, together with the lower region of air in conthough most commonly, in the day time. The tact with it, so that the said lower air becomes terrible whirlwind, which damaged a great specifically lighter than the superincumbent part of Rome, June 11, 1749, happened in the higher region of the atmosphere, in which the night of that day. The same was supposed clouds commonly float: let us suppose, also, to have been first a spout, for it is said to be that the air surrounding this tract has not been beyond doubt, that it gathered in the neigh- so much heated during those days, and therebouring sea, as it could be tracked from Ostia fore remains heavier. The consequence of to Rome. I find this is in Père Boschovich's this should be, as I conceive, that the heated account of it, as abridged in the Monthly Re- lighter air, being pressed on all sides, must view for December, 1750.
ascend, and the heavier descend; and, as this In that account, the whirlwind is said to rising cannot be in all parts, or the whole area have appeared as a very black, long, and lofty of the tract at once, for that would leave too cloud, discoverable, notwithstanding the dark- extensive a vacuum, the rising will begin ness of the night, by its continually lightning precisely in that column that happens to be or emitting flashes on all sides, pushing along the lightest, or most rarefied; and the warm with a surprising swiftness, and within three air will flow horizontally from all points to or four feet of the ground. Its general effects this column, where the several currents meeton houses, were stripping off the roofs, blow- ing, and joining to rise, a whirl is naturally ing away chimneys, breaking doors and win- formed, in the same manner as a whirl is dows, forcing up the floors, and unpaving the formed in the tub of water, by the descending rooms (some of these effects seem to agree fluid flowing from all sides of the tub, to the well with a supposed vacuum in the centre hole in the centre. of the whirlwind) and the very rafters of the And, as the several currents arrive at this houses were broken and dispersed, and even central rising column, with a considerable dehurled against houses at a considerable dis- gree of horizontal motion, they cannot sudtance, &c.
denly change it to a vertical motion; thereIt seems, by an expression of Père Boscho-fore as they gradually, in approaching the vich's, as if the wind blew from all sides to whirl, decline from right curved or circular wards the whirlwind ; for, having carefully lines, so, having joined the whirl, they asobserved its effects, he concludes of all whirl-cend by a spiral motion, in the same manner winds, “ that their motion is circular, and their as the water descends spirally through the hole action attractive."
in the tub before-mentioned. He observes, on a number of histories of Lastly, as the lower air, and nearest the whirlwinds, &c. “ that a common effect of surface, is most rarefied by the heat of the them is, to carry up into the air, tiles, stones, sun, that air is most acted on by the pressure and animals themselves, which happen to be of the surrounding cold and heavy air, which in their course, and all kinds of bodies unex- is to take its place; consequently, its motion ceptionably, throwing them to a considerable towards the whirl is swiftest, and so the force distance, with great impetuosity."
of the lower part of the whirl, or trump, Such effects seem to show a rising current strongest, and the centrifugal force of its parof air.
ticles greatest ; and hence the vacuum round I will endeavour to explain my conceptions the axis of the whirl should be greatest near of this matter by figures, representing a plan the earth or sea, and be gradually diminished and an elevation of a spout or whirlwind. approaches the region of the clouds, till