XLIV. Of the stilling of waves by means of oil. Extracted from sundry letters between Benjamin Franklin, LL. D. F. R. S. William Brownrigg, M. D. F. R. S. and the Reverend Mr. Farish f 445 J XL IV, O f the fillin g o f Waves by meant o f Oil. ExtraSied from fundry Letters between Benjamin Franklin, L L . F. R r S. William Brownrigg, M. F. R. S.and the Reverend M r. Farifti. Extract o f a Letter from- D o d o r b r o w n r ig g to Br* f r a n k l i n , dated Ormathwait, January 27 l7Tir Y the enclofed from an old friend, a J 3 worthy clergyman at Carlifle, whofe great learning and extenfive knowledge in moft fai­ ences would have more diftinguifhed him , had he been placed in a more confpicuous point o f view, you will find that he had heard of your experi­ ment on Derwent Lake, and has thrown together what he could colled on that fu b je d 5 to which I have fubjoined one experiment from the relation o f another Gentleman.. ; , E x trad of a Letter from the Reverend M r. f a r i s h * to Dr. b r o w n r ig g . I fom etim e ago met with M r. D un, who fur- prjfed me with an account of an experiment you had tried upon the Derwent water, in company with Sir D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 Sir jo h n p r in g l e and Dr. f r a n k l i n . According to his reprefentation, the water, which had been in great agitation before, was inftantly calmed, upon pouring in only a very fmall quantity o f oil, and that to fo great a diftance round the boat as feems a little incredible. I have fince had the fame accounts from others, but I fufpedt all of a little exaggeration. p l in y mentions this property of oifas known parti­ cularly to the divers, who made ufe of it in his days, in order to have a more fteady light at the bottom(tf). T h e failors, I have been told, have obferved fome- thing of the fame kind in our days, that the water is always remarkably fmoother in the wake of a ihip that hath been newly tallowed, than it is in one that is foul. — Mr. p e n n a n t alfo mentions an obferva- tion of the like nature made by the feal catchers in Scotland. B rit. Zool. Vol. iv . Article s e a l . W h e n thefe animals are devouring a very oily fifh, which they always do under water, the waves above are obferved to be remarkably fmooth, and by this mark the filhermen know where to look for them. — Old p l i n y does not ufually meet with all the credit I am inclined to think he deferves. I (hall be glad to have an authentic account of the Kefwick experiment, and if N o te by D r. brownrigg. (a) Sir gilfred lawson, who ferved long in the army at Gibraltar, allures me that the filhermen in that place are ac- cuftomed to pour a little oil on the Tea, in order to ftill its motion, that they may be enabled to fee the oyfters lying at its bottom ; which are there very large, and which they take up with a pro­ per inftrument. T h is Sir gilfred had often fecn there per­ formed, and faid the fame was pra&ifed on other parts o f the Spanifh coaft. [ 446 ] it D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ +47 ] , . . it comes up to the reprefentations that have been made o f It* I (hall not much hefltate to believe the old Gentleman in another more wonderful pheno­ menon, he relates, of billing a tempeft only by throwing up a little vinegar into the air, Extradfc of a L etter to Do&or b r o w n r ig g from D o d o r FRANKLIN. London, N o v , 7,- 1 773. BEAR SIR, v ' I thank you for the remarks o f your learned ^ Carlifle. — I had, when a youth, read and Innled at p l in y ’s account o f a pradice among the feamen of his time, to ftill the waves in a ftorm by, pouring oil into the fea; whjch he mentions, as well, as the ufe made of oil by the divers; but the ftilling a tempeft by throwing vinegar into the air had efcaped me. I think with your friend, thatit has been of late too . much the mode to flight the learning of the antients. 'The learned, too, are apt to flight too much the knowledge of the vulgar. T h e cooling by evapora­ tion was long an inftance of the latter. This art o f imoothing the waves with oil, is an inftance o f both, rem aps you may not diflike to have an account 01 all I have heard, and learnt, and done in this waY\ Tahe it . if you pleafe as follows.' L J^in g at fea in a fleet of 96, fail bound • QU1̂ 30ur§> I obferved the wakes o f two of the fhips to be remarkably frnooth,. while all the others were ruffled by the wind, which blew frefh. xjeing puzzled w ith the differing appearance, I at laft pointed D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 I 4+8 ] pointed it out to our captain, and afked him th e m eaning o f it ? fl T h e cooks, fays he, have, I fuppofe, been*, ju ft em ptying their greafy w ater th ro u g h th e fcuppers, w hich has greafed the fides o f thofe fhips a little }” and this anfwer h e gave m e w ith an air o f fome little contem pt, as to a perfon ignorant o f w h at every body elfe knew . In m y ow n m ind I at firft flighted his folution, tho* I was n o t able to th in k o f another. But recollecting w hat I had form erly read in p l i n y , I refolved to m ake fome experim ent o f the effeCt o f oil on w ater, w hen L fhould have op­ portunity. . f V Afterwards being again at fea in 1762, I firft o b - ferved the wonderful quietnefs o f oil on agitated water, in the Twinging glafs lam p I m ade to han g up in the cabin, as defcribed in m y printed papers, page 43 8 o f the fourth edition. — T h is I was continually looking at and confidering, as an appearance to m e inexplicable. A n old fea captain, then a paflenger w ith m e, th o u g h t little o f it, fuppofing it an efteCt o f th e fame kind w ith that o f oil pu t on water to fm ooth it, w hich he faid was a practice o f the Be r ­ m u d i a n s w hen they w ould ftrike fi{h, w hich they * could not fee, i f the furface o f the w ater was ruffled by the wind. T h is practice I had never before heard of, and was obliged to him for the inform ation ; tho* I thought him m iftaken as to the famenefs o f th e experim ent, the operations being different; as w ell as the effects. In one cafe, the water is fm ooth till the oil is p u t on, and then becomes agitated. I n the other it is agitated before the oil is applied, and then becomes fmooth* — T h e fame gentlem an told m e, he had heard it was a practice w ith the fifher- m en D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 fnen of Lisbon when about to return into the river, (if they faw before them too great a furf upon the bar, which they apprehended might fill their boats in palling) to empty a bottle or two of oil into the fea, which would fupprefs the breakers, and allow them to pafs fafely : a confirmation of this I have not fince had an opportunity o f obtaining. But dif- courfing of it with another perfon, who had often been in the Mediterranean, I was informed that the divers there, who, when under water in their bufinefs, need light, which the curling o f the furface inter­ rupts by the refra&ions of fo many little waves, let a final! quantity of oil now and then out of their mouths, which riling to the furface fmooths it, and permits the light to come down to them. — All thefe informations I at times revolved in my mind, and wondered to find no mention of them in our books of experimental philofophy. A t length being at c l a p h a m where there is, on the comtnon, a large pond, which I oblerved to be one day very rough with the wind, I fetched out a cruet o f oil, and dropt a little o f it on the water. I law it fpread itlelf with lurprizing fwiftnels upon the furface $ but the efieft o f fmoothing the waves was not produced; for I had applied it firfi: on the leeward fide o f the pond, where the waves were large#, and the wind drove my oil back upon the fhore. 1 then went to the windward fide, where they began to * form ; and there the oil, though not more than a tea fpoonful, produced an infiant calm over a fpace feveral yards fquare, which fpread amazingly, and extend­ ed itfelf gradually till it reached the lee fide, making all that quarter o f the pond, perhaps half an acre* as fmooth as a looking-glafs. [ 449 ] V ol. L X I V . M m m Afte D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 A fter this, 1 contrived to take w ith m e, w henever I w ent into the country, a little oil in th e upper hol­ low jo in t o f m y bam boo cane, w ith w hich 1 m ig h t repeat the experim ent as opportunity fhould offer j and I found it constantly to lucceed. I n thefe experim ents, one circum ftance ftruck m e w ith particular furprize. T h is was the fudden, wide,., and forcible fpreading o f a drop o f oil on the face o f the w ater, w hich I do not know that any body has h-itherto confidered. I f a drop o f oil is put on a polifhed m arble table, or on a looking-glals that lies horizontally ; the drop remains in its place, fpread- ing very little. B ut w hen p u t on w ater it Ipreads initantly m any feet round, becom ing fo thin as to. produce the prilm atic colours, for a confiderable fpace, and beyond them fo m uch th in n er as to be invilible, except in its effect o f fm oothing th e waves at a m u ch greater diftanee. I t feems as if a m utual repulfion between its particles took place as loon as it touched the w ater, and a repulfion lb ftrong as to abt on other bodies fw im m ing on the furface, as d raw s, leaves, chips, & c. forcing th em to recede every way from th e drop, as from a center, leaving a large clear fpace. T h e quantity o f this force, and the diftanee to w hich it will operate, .1 have not yet afeertairted b u t I th in k it a curious enquiry, and I wifh to u n d erh an d w hence it arifes. In our jo u rn ey to the n orth, w hen we had th e plea- fure o f feeing you at O rm ath w aite, w e vifited the cele­ brated M r. s m e a t o n near L eeds. B eing about to fhew h im the fm oothing experim ent on a little pond near his houfe, an ingenious pupil o f his, M r. Jeflop, then prelent, told us o fa ii odd appearance on th a t pond, 2 w hich [ 450 ] D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ 4 5 i ] which had lately occurred to him. He was about to, clean a little cup in which he kept oil, and he threw upon the water lim e flies that had been drowned in theoil. Thefe flies prefently began to move, and turn­ ed round on, the water very rapidly, as if they were vigoroufly alive, though on examination be found they were not fo. I immediately concluded that the motion was occafioned by the power of the repulfion abovementioned, and that the oil ifluing gradually from the fpungy body of the fly continued the mo­ tion. H e found fome more flies drowned in oil, with which the experiment was repeated before us. T o lhew that it was not any effe& of life , recovered by the flies, 1 imitated it by little bits of oiled chips and paper cut in the form of a comma, of the lize of a common fly ; when the Aream of repelling particles ifluing from the point, made the comma turn round the contrary way. This is not a chamber experiment; for it cannot well be repeated in a bowl or difh o f water on a table. A confiderable furface of water is neceffary to give room for the expanfion of a final! quantity of oil. In a difh of water, if the fmalleft drop o f oil be let fall in the middle, the whole fur- face is prefently covered with a thin greaiy film pro­ ceeding from the drop; but as foon as that film has reached the fides of the difh, no more will ifluefrom the drop, but it remains in the form of oil, the fides of the difh putting a flop to its diffipation by pro­ hibiting the farther expanfion of the film. Our friend Sir John p r in g l e being foon after in Scotland, learnt there, that thofe employed in the herring fifhery, could at a diftance fee where the Ihoals o f herrings were, by the fmoothnefs of the M m m 2 wat?r D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 C ] water over them , w hich m ight poftibly be occafion- ed, he ̂ thought, by fbme oilinefs proceeding from their bodies. A gentlem an from Rhode-ifland told m e, it had been rem arked that the harbour o f N ew port was ever fmooth while any whaling veftels were in it w hich probably arofe from hence, th at the blubber w hich they fbmetimes bring loofe in the hold, or th e leakage o f their barrels, m ight afford fome oil, to mix: w ith that water, w hich from tim e to tim e th e y p u m p o u t to keep the veftel free, and that fame oil m ight fpread over the furface of the water in the harbour, and prevent the form ing o f any waves. T h is prevention I would thus endeavour to explain. T h e re feems to be no natural repulfion betw een w ater and air, fuch as to keep them from com ing into contact w ith each other. H ence we find a quantity o f air in w a t e r ; and if we extradl it by means o f the air-p u m p , th e fam e water again ex - pofed-to the air, will foon im bibe an equal quantity. T herefore air in m otion, w hich is wind, in palling over the fm ooth furface o f w ater, may ru b , as i t were, upon that furface, and raife it into w rinkles, w hich, if the w ind continues, are the elem ents o f future waves. T h e fmal left wave once raifed does not im m edi­ ately fubftde, and leave the neighbouring water q u ie t: but in fubfiding raifes nearly as m uch o f the w ater next to it, the friction o f the parts m aking lit­ tle difference. T h u s a ftone dropt in a pool raifes firft a fingle wave round itfe lf; and leaves it, by finking to the bottom $ but th a t firft wave fubfiding raifes a fecond, the fecond a third, and fo on in circles to a grea t extent, J: A fsna!I D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 L 453 ] A fmall power continually operating will produce a great adion. A finger applied to a weighty fuf- pended bell, can at firft move it but little; if re­ peatedly applied, though with no greater ftrength, the motion increafes till the bell fwings to its utmoft height, and with a force that cannot be refilled by the whole ftrength of the arm and body. T h u s the fmall firft-raifed waves, being continually a died up­ on by the wind, are, though the wind does not in- creafe in ftrength, continually increafed in magni­ tude, riling higher and extending their bafes, fo as to include a vaft mafs of water in each wave, which in its motion ads with great violence. But if there be a mutual repulfion between the particles of oil, and n6 attradion between oil and water, oil dropt on water will not be held together by adhelion to the fpot whereon it falls; it will not be imbibed by the water ; it will be at liberty to ex­ pand itlelf; and it will fpread on a furface that, be- fides being finooth to the moft perfect degree of polilh, prevents, perhaps by repelling the oil, all im mediate contad, keeping it at a minute diftance from itfelf; and the expanlion will continue, till the m u ­ tual repullion between the particles of the oil is weakened and reduced to nothing by their diftance. Now I imagine that the wind blowing over water thus covered with a film of oil, cannot eafiiy catch upon it, fo as to raife the firft wrinkles, but ilides over it, and leaves it lmooth as it finds it. It moves a little the oil indeed, which, being between it and the water, ferves it to Hide with, and prevents fridion, as oil does between thofe parts of a machine, that would otherwife rub hard together, Hence the D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ 454 ] , ’• oil dropt on the w indw ard fide o f a pond proceeds gradually to leeward, as may be feen by the fm ooth- nefs it carries w ith it, quite to the oppofite fide. F or the wind being thus prevented from railing th e tirfi: wrinkles that I call the elem ents o f waves, cannot produce waves, which are to be m ade by continual­ ly acting upon and enlarging tbofe elements, and thus the w hole pond is calmed. T o tally therefore we m ight fupprefs the waves in any required place, if we could com e at the w ind­ ward place w here they take th eir rile. T h is in t h e . ocean can feldom i f ever be done. B ut perhaps fom ething may be done on particular occalions, to m oderate the violence o f th e waves, w hen we are in the m idif o f them , and prevent their breaking, w here that would be inconvenient. F o r when the w ind blows frelh, there are con­ tinually riling on the back o f every great wave, a num ber o f lm ail ones, w hich roughen its furface, and give the w ind hold, as it were, to pulh it w ith greater force. T h is hold is dim inilhed by prevent­ ing the generation o f thofe fmall ones. A nd pof- fibly too, when a wave’s furface is oiled, the w ind, in palling over it, may rather in fome degree prefs » it dow n, and contribute to prevent its riling again, inftead o f prom oting it. T h is as mere conjecture would have little w eight, if the apparent effects o f pouring oil into the mid ft o f waves were not confiderable, and as yet not otherw ife accounted for. W h e n the wind blows fo frelh, as that the waves are not fufficiently quick in obeying its impulfe, their tops being thinner and lighter are pufhed forw ard, • ' broken, D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 broken, and turned over in a white foam. Com­ mon waves lift aveflel, without entering it; but thele when large fometimes break above and pour over it, doing great damage. T h a t this effed might in any degree be prevent­ ed, or the height and violence of waves in the fea moderated, we had no certain account ; p l i n y ’s authority, for the pra&ice of Teamen in his time being flighted. But difcourfing lately on thisfubjed with, his excellency Count ben t i n ck of Holland, his fon the honourable Captain b e n t i n c k , and the learns ed profeffor a l l e m a n d , (to all whom I fhewed the experiment of lmoothing in a windy day the large piece of water at the head of the Green P a rk ; ) ; a letter was mentioned which had been received by the Count from Batavia, relative to the faving o f a D utch fliip in a ftorm, by pouring oil into the fea. I much deli red to fee that letter, and a copy of it: was promifed me, which I afterward received W . (b) Extrait d’une Leltre de Mr. tengnagel a Mr. le Comte de bentinck,, ecrite de Batavia ie 15 Janvier, 1770. ^Presdes iflesPaulus &. Amfterdam nous efluiames un orage, qui > n’eut rien d’aflez particulier pour vous etre marque, ft non que riotre capitaine fe trouva oblige en tournant fous le vent, de verfer de Thuile contre la haute mer, pour empecher les vagues de fe brifer conrre le navire, ce qui reuffit a nous conferver, & a e,e d’un tres bon effet; comrne il n’en verfa qu’une petite quantite a la fois, la compagnie doit peut-etre fon vaiffeau a fix demi aumes d’huile d’olive : j ’ai ete prefent quand cela s’eft fait, & je ne vous aurois pas entretenu de cette circonftance, fi ce n’etoit quenousavons trouve les gens ici fiprevenus con trel’experience, que les officiers du bord nj moi n’avons fait aucune difficult^ d e/ donner un certificat de la verite fur ce chapitre. C 455 ] Extra# D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ 4 5 6 ] « E x tract o f a L etter from M r, t e n g n a g e l to . and believe m e to be, w ith lincere efteem , DEAR SIR, • * Y our m o d obedient hum ble fervant, B. F R A N K L I N , X L V . Translation D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1