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mnfter and mate of the Bafil, Mr. Hutchlnfoii was informed, 

 that thofe people belonged to a fchooner bound from Ber- 

 Buidas to the Weft Indies ; that it was after a hard gale of 

 wind when they met with the boat, which had two oars for 

 mafts, and two blankets fet upon them for fails, and was 

 ftcering for Bermudas, when they were fortunately taken up ; 

 and that the log of wood, as it was called, they drove by, 

 was riieir fore fquare-fail-yard, fpanned with a rope to each 

 jtprd-arm, and a rope about ten or twelve fathoms long bent 

 to the middle of the fpan, and made fall to the boat's bow, 

 to drive by. The mate of the fchooner told the mailer of 

 the Balil, that they had been favtd in this manner in a boat 

 once before, by driving to leeward of a mall, in a hurricane 

 in t'he Weft Indies. 



In order to account for this wonderful effeft of the drift- 

 boom, in preventing the broken water from fwamping the 

 boat, it may be obfcrved, fays Mr. Hutchinfon, that waves 

 never break till their tops are forced forwards by their great 

 velocity beyond the perpendicular of their bafe ; then that 

 water falls down forward, and inclofes and compreffes 

 a quantity of air, which, by the power of its elafticity, blows 

 this fore-part of the waves to pieces, forwards and upwards, 

 in an oblique direflion, and makes it appear like froth. 

 They then have no buoyant power to lift a boat ; but when 

 they are high, they fill and fink her. And they break more 

 in (hoal water than in deep, in proportion as their bottoms 

 or bafe are more obftruftcd in their velocity by the ground 

 than their tops ; hence, in very fiioal water, they are conti- 

 nu-ally breaking, fo that they make nothing but what is 

 called broken water, by which ftioals may be feen and known 

 at a great diftance in cleai' weather. 



If we endeavour to account for the wonderful effedl of fo 

 fmall and fimple a machine, to pi-tferve fuch a fmall boat, 

 deeply laden as file mutt be with ten men, from being filled 

 with water in fuch a ftorm ; in our opinion, it is owing to 

 the boat driving end on by the drift boom, that keeps it al- 

 ways fwimming on the fnrface, broadfide to the wind ; and 

 the waves that are running towards it, within the length of 

 the drift boom, mull certainly obftruft the velocity of the 

 tipper part of thefe waves, fo as to Icffen their increafe in 

 height, and prevent the top from running beyond the per- 

 pendicular of the bafe, or bottom of thefe waves, that occa- 

 fions their breaking, as has been defcribed, but fpend them- 

 felves without breaking. Thefe reafons, we hope, will be 

 thought fufficient to recommend this method to be tried and 

 brought into practice on fuch dreadful occafions : and we can- 

 not help thinking, that the fame method {hould be tried, 

 when under the dreadful neceflity of faving lives by boats 

 landing on a lee ftiore in a ftorm, where broken waves run 

 high. The only difference we would recommend in the ma- 

 nagement, is to proceed with the boat's ftern to the drift 

 boom, and her head to the Ihore, to be ready to row and 

 fteer for the beft apparent landing-place ; and if it is a long- 

 flat ftiore, as foon as the boat (hikes the ground, cut or flip 

 the drift boom rope, that it may not haul the boat off the 

 ftiore again by the back fweep of the waves. 



Upon landing a boat in a J'nrf. Before the boat comes 

 near the fhore, pour a little oil on the water, which will pre- 

 vent its breaking, and greatly allay the fwell, fo that the boat 

 may approach the fhore without the dread of being fwallowed 

 up in the breakers. 



M. Danzcl has lately invented an hydraulic machine for 

 making a ftiip or boat advance during a calm, and even 

 againft a current. 



The mechanifm of this machine is very fimple ; it confifts 

 of a long pole, to the anterior extremity of which an appa- 



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ratus, fliaped like a drawer without back or front is at- 

 tached in fuch a manner, that when puflied forwards it folds 

 itfelf back under the pole, to which it (as it were) adheres, 

 and prefents to the water the thin cutting furface of its 

 three edges, viz. of the bottom and two fides, v/hich can 

 neither oppofe to the water a refiftance capable of prevent- 

 ing the pole from penetrating farther, or of making the ftiip 

 recede. When the pole, which is pufiied forwards from the 

 veffel, has attained to its full reach, the drawer, as foon as 

 the pole is pulled back, alfumes a vertical pofition, and pre- 

 fents to the water its whole cavity. By thefe means it em- 

 braces a column of water, which, without finding means to 

 efcape, preffes on a furface much larger than that of a com- 

 mon oar, and keeps the drawer immoveable ; fo that thofe 

 who draw the pole towards them, iuftead of making the 

 veflel to recede, caufe it to advance. This machine, which 

 may be multiplied more conveniently than oars, has this 

 vifible advantage over the latter, that it oppofes to the wa- 

 ter a refiftance infinitely fuperior, while the paflive re-adtiori 

 of this refiftance renders the labour of the mariners lefs la- 

 borious End more effeftual. 



De Chales propofes the conftruftion of a boat, which, 

 what burden foever it bear, (hall not only move again 11 the 

 current, without either fails or oars, but alfo advance fo much 

 the fafter, as the rapidity of the water is greater. Its make 

 is the fame with that of the others, excepting only a wheel 

 added to its fide, with a cord, which winds round a roller as 

 faft as the wheel turns. 



Something of the like kind has alfo been fince done by 

 M. Pitot. Vide Mem. Acad. R. Scienc. an. 1729. p. 35y, 

 and p. 540. 



M. de la Hire has given us an examination of the force 

 neceflary to move boats, both in ftagnantand running water, 

 either with ropes faftened to them, or with oars, or with any 

 other machine : wherein he Ihews, that the larger the fur- 

 face of the oars plunged in the water, and the imaller that 

 of the boat prefented to the water, is ; and again, the 

 longer that part of the oar between the hand and the places 

 where the oar refts on the boat, and the ftiorter that between 

 this lail point and the water ; the freer will the boat move, 

 and the greater effecl will the oar have. See Oar. 



Hence it ;s eafy to calculate the force of any machine that 

 ftiall be applied to rowing ; v. gr. if we know the abfolute 

 force of all the men who row, it muft be changed into a 

 relative force, according to the proportion of the two parts 

 of the oar ; i. e. if the part out of the veffel be double the 

 other, and all the men together can aft with the force of 

 900 pounds, we compute firft, that they will exert ,300 ; 

 vi'hich 300, multiplied by the furface which the velfcl pre- 

 fents to the water, gives a folid water of a certain weight ; 

 which weight may be found, and of confequence the veloci- 

 ty imprefled on the velfel by the oars. Or, the velocity of 

 the oars may be found in the fame manner, by multiplying 

 the 300 pounds by the furface of all tlie parts of the oars 

 plunged in the water. Nor would there be any difficulty 

 in finding firft the relative forces, then the abfolute ones ; 

 the velocities either of the oars, or of the veffel, being given, 

 or the proportion of the two parts of the oar. 



Boats fail more flowly and heavily over ftiallow than over 

 deep waters. See an account of experiments for explaining 

 this, in Dr. Franklin's Letter to St. John Pringle. E-t- 

 periments, &c. 410. 5th ed. p. 510. 



Boats, Conjlruaion of. In order to illuftrate this by an 

 example, let it be required to lay down the feveral plans ofa 

 long boat, the extreme length being 3 1 feet, and breadth 

 moulded 9 feet. 



Draw 



