« ZurückWeiter »
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 approach of that the water really descends in some of some suitable foreign collection, accidentally 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, I leave. 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 should serve for descending. your amusement, or any way oblige you, it is It has not yet been proved that any one all I aim at, and shall, at your desire, be al- spout ever ascended. A specious appearance ways ready to say what I think, as I am sure is all that can be produced in favour of this; of your candour.
and those who have been most positive about 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.--Read at the cends or descend at half the distance. Royal Society, July 8, 1756.
It may not be amiss to consider the places Spouts 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, whenee sudden and wonderful conas they think, and all agree the descent 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 appearance 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,
I 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 a 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 fulls 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 inuch 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 onc 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 yravitanot 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, tices 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 superone.
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 with air, it would weigh at least as much less, | less motion, and not suddenly acquiring the as this difference between the weight of that quicker motion of the equatorial earth, apincluded air, and that of water.
pears an east wind blowing westward; the Now although this would do nothing to ac-earth moving from west to east, and slipping count for the dissolution of salt in water, under the air." the smallest lumps of salt being no more In reading this, two objections occurred to hollow spheres, or any thing of the like na- my mind :-First, that it is said, the tradeture, than the greatest; yet, perhaps, it might wind doth not blow in the forenoon, but only account for water's rising and being support in the afternoon. ed in air. For you know that such hollow Secondly, that either the motion of the globules, or bubbles, abound upon the surface northern and southern air towards the equaof the water, which even by the breath of our tor is so slow, as to acquire almost the same mouths, we can cause to quit the water, and motion as the equatorial air when it arrives rise in the air.
there, so that there will be no sensible differThese bubbles I used to suppose to be the ence; or else the motion of the northern and coats of water, containing within them air southern air towards the equator, is quicker, rarefied and expanded with fire, and that and must be sensible; and then the tradetherefore, the more friction and dashing there wind must appear either as a south-east or is upon the surface of the waters, and the north-east wind : south of the equator, a southmore heat and fire, the more they abound. east wind; north of the equator, a north-east.
And I used to think, that although water for the apparent wind must be compounded be specifically heavier than air, yet such a of this motion from north to south, or vice bubble, filled only with fire and very rarefied versa ; and of the difference between its moair, may be lighter than a quantity of com- tion from west to east, and that of the equamon air, of the same cubical dimensions, and, torial air. therefore, ascend; for the rarefied air enclosed, may more fall short of the same bulk of common air, in weight, than the watery coat --Reid at the Royal Society, Nov. 4, 1756.
Observations in answer to the foregoing. exceeds a like bulk of common air in gravity:
This was the objection in my mind, though, 1st. The supposing a mutual attraction beI must confess, I know not how to account tween the particles of water and air, is not for the watery coat's encompassing the air, introducing a new law of nature; such atas above-mentioned, without allowing the at- tractions taking place in many other known traction between air and water, which the instances. gentleman supposes; so that I do not know Ally. Water is specifically 850 times heabut that this objection, examined by that sa- vier than air. To render a bubble of water, gacious genius, will be an additional confirm- then, specifically lighter than air, it seems to ation of the hypothesis.
me that it must take up more than 850 times The gentleman observes, " that a certain the space it did before it formed the bubble ; quantity of moisture should be every moment and within the bubble should be either a vadischarged and taken away from the lungs; cuum or air rarefied more than 850 times. It and hence accounts for the suffocating nature vacuum, would not the bubble be immediateof snuffs of candles, as impregnating the airly crushed by the weight of the atmosphere? with grease, between which and water there And no heat, we know of, will rarely air any is a natural repellency; and of air that hath thing near so much; much less the common been frequently breathed in, which is over- heat of the sun, or that of friction by the dashloaded with water, and, for that reason, can ing on the surface of the water: besides, watake no more air. Perhaps the same obser- ter agitated ever so violently produces no heat, vation will account for the suffocating nature as has been found by accurate experiments. of damps in wells.
3dly. A hollow sphere of lead has a firmBut then if the air can support and take off ness and consistency in it, that a hollow but such a proportion of water, and it is ne- sphere or bubble of fluid unfrozen water cancessary that water be so taken off from the not be supposed to have. The lead may suplungs, I queried with myself how it is we can port the pressure of the water it is immerged breathe in an air full of vapours, so full as in, but the bubble could not support the presthat they continually precipitated. Do not we sure of the air, if empty within. see the air overloaded, and casting forth wa- 4thly. Was ever a visible bubble seen to ter plentifully, when there is no suffocation? rise in air ? I have made many, when a boy,
The gentleman again observes, “ That the with soap-suds and a tobacco-pipe ; but they air under the equator, and between the tro- all descended when loose from the pipe, though pics, being constantly heated and rarefied by slowly, the air impeding their motion : they the sun, rises; its place is supplied by air from may, indeed, be forced up by a wind from beporthern and southern latitudes, which, com- low, but do not rise, of themselves, though ing from parts where the air and earth had filled with warm breath.
5thly. The objection relating to our breath- | Observations on the Meteorological Paper ing moist air seems weighty, and must be sent by Cadwallader Colden, of New York, farther considered. The air that has been to B. Franklin.-Read at the Royal Society, breathed has, doubtless, acquired an addition Nov. 4, 1756. of the perspirable matter which nature intends to free the body from, and which would be That power by which the air expands itpernicious if retained and returned into the self, you attribute to a mutual repelling powblood : such air then may become unfit for er in the particles which compose the air, by respiration, as well for that reason, as on ac- which they are separated fro each other count of its moisture. Yet I should be glad with some degree of force; now this force, to learn, by some accurate experiment, whe- on this supposition, must not only act when ther a draft of air, two or three times inspir- the particles are in mutual contact, but likeed, and expired, perhaps in a bladder, has, or wise when they are at some distance from has not, acquired more moisture than our each other. How can two bodies, whether common air in the dampest weather. As to they be great or small, act at any distance, the precipitation of water in the air we breathe, whether that distance be small or great, withperhaps it is not always a mark of that air's out something intermediate on which they being overloaded. In the region of the clouds, act? For if any body act on another, at any indeed, the air must be overloaded if it lets distance from it, however small that distance fall its water in drops, which we call rain; but be, without some medium, to continue the acthose drops may fall through a drier air near tion, it must act where it is not, which to me the earth; and accordingly we find that the seems absurd. hygroscope sometimes shows a less degree It seems to me, for the same reason, equalof moisture, during a shower, than at other ly absurd to give a mutual attractive power times when it does not rain at all. The dewy between any other particles supposed to be at dampness, that settles on the insides of our a distance from each other, without any thing walls and wainscots, seems more certainly to intermediate to continue their mutual action. denote an air overloaded with moisture; and I can neither attract nor repel any thing at a yet this is no sure sign : for, after a long distance, without something between my continued cold season, if the air grows sud- hand and that thing, like a string, or a stick; denly warm, the walls, &c. continuing longer nor can I conceive any mutual action without their coldness, will, for some time, condense some middle thing, when the action is continuthe moisture of such air, till they grow ed to some distance. equally warm, and then they condense no The increase of the surface of any body more though the air is not become drier. lessens its weight, both in air, and water, or And, on the other hand, after a warm season, any other fluid, as appears by the slow descent if the air grows cold, though moister than be- of leaf-gold in the air. fore, the dew is not so apt to gather on the The observation of the different density of walls. A tankard of cold water will, in a the upper and lower air, from heat and cold, hot and dry summer's day, collect a dew on is good, and I do not remember it is taken noits outside; a tankard of hot water will col- tice of by others; the consequences also are lect none in the moistest weather.
well drawn; but as to winds, they seem prin6thly. It is, I think, a mistake that the cipally to arise from some other cause. trade-winds blow only in the afternoon. They Winds generally blow from some large tracts blow all day and all night, and all the year of land, and from mountains. Where Dive, round, except in some particular places
. The on the north side of the mountains, we fresoutherly sea-breezes on your coasts, indeed, quently have a strong southerly wind, when blow chiefly in the afternoon. In the very they have as strong a northerly wind, or calm, long run from the west side of America to on the other side of these mountains. The Guam, among the Philippine Islands, ships continual passing of vessels on Hudson's seldom have occasion to hand their sails, so River, through these mountains, give frequent equal and steady is the gale, and yet they opportunities of observing this. make it in about 60 days, which could not In the spring of the year the sea-wind (by be if the wind blew only in the afternoon. a piercing cold) is always more uneasy to me,
7thly. That really is, which the gentleman accustomed to winds which pass over a tract justly supposes ought to be, on my hypothesis of land, than the north-west wind. In sailing southward, when you first enter the You have received the common notion of trade-wind, you find it north-east, or there water-spouts, which, from my own ocular abouts, and it gradually grows more east as observation, I am persuaded is a false concepyou approach the line. The same observa- tion. In a voyage to the West Indies, I had tion is made of its changing from south-east an opportunity of observing many waterto east gradually, as you come from the south- spouts. One of them passed nearer than ern latitudes to the equator.
thirty or forty yards to the vessel I was in.