« السابقةمتابعة »
if we are not greatly mistaken, the insinuation had then never appeared.
Having finished his introduction, Mr. Murray proceeds to make extracts from M. Bouguer's Traité dit Navire, and from comparing fome of them with the original, they appear, to be done with sufficient accuracy. His own remarks also which regard the practical part of thip-building, are very proper, and tend to elucidare the subject. We wish we could say the same with regard to those made on the mathematical processes; but in our opinion, the work would not have been at all the less valuable, if these had been wholly omitted. Thus in pag. 49, our author seems to blame Mr. Bouguer for introducing a fluxionary investigation of the line of the angle of incidence; and instead of the Frenchman's process, has given another method of his own for finding it by the doctrine of right-angled triangles. But it may not be amiss to hint to our Author, that the side Ee in his own figure, is not a right-line, but a curve; and that it was for this very reason that M. Bouguer had recourse to a fluxionary process. We could therefore with, that Mr. Murray had contented himself with giving the result of these curious investiga,
tions of his author. Had he pursued this method, we should not · have seen the weak remarks he has made in the following page, - on the solution of one of the most intricate and curious problems in mechanics. :
It would extend this article too far, if we attempted to give the fubftance of the work before us, which is only a concise abridgment of a much larger treatise; we shall therefore content our
selves with giving the substance of M. Bouguer's conclufion, . as translated by Mr. Murray.
"After having, to the utmost of my power, says our author, executed every part of the engagement I undertook, it will be proper now to recapitulate the principal things I have explained, especially such as relate to the figure of the ship; and I shall make no scruple again to affirm, that, I believe, I have given infallible rules to the builders, to determine their choice of the different plans that may be presented to them of the same ship. We have, in the second book, explained all that concerns a fhip while a-float or at rest : we may know if the whole weight be proportional to the solidity of the immerged part; if she has stability or force to carry fail; or if the carries her guns high enough out of the water : and, in the third book, we have given proper rules to assure us she will fail well; drive but liitle, when close hauled upon the wind, and readily answer all the motions of the helm. All the other qualities are submitted to the proof of a . calculation, which costs but little labour : even such accidents as seem to depend on very irregular causes are considered; such as the duration of the vibrations occasioned by rowling, and
tribution ofupported in ink no la
those of pitching; we máy judge of them by examining the diftribution of the weights, and in what manner every particular weight is supported in every different circumstance. . • Geometricians think no labour too hard, and do not satisfy themselves with what knowledge they have acquired, but are continually pushing their researches to the highest pitch ; notwithstanding all this, we must sometimes have recourse to experiments on ships already built, which may serve as a term of comparison. By these experiments we may, in an instant, discover things which could not be done any other way, without a greač deal of labour; and, in forming another ship, it may sufice to take notice of their different dimensions, and the necessary causes that may occasion some alterations.
We have endeavoured, out of an infinite number of forms, to pick out the best ; and where the disposition of different parts contribute to carry a certain property to a higher degree, we have searched the most advantageous combination, to determine the maximum. We may, with certainty, make which property we please predominate, and at the same time know how far we may
carry the others. PAWe have thewn, that the extreme breadth should be five
twelfths of the length, from the forepart, which is the position best suited to make the ship answer the motions of the helm; but it must be carried a little further forward, to inake her iteer well by the affiftance of the rails, though, by this means, the bow will become fuller, to the prejudice of her sailing, and of that property which should make a ship lels subject of driving to the leeward. It will be imposible to reconcile these four properties; and, that we may not lose too much of any one of thein, we must resolve to lose a part of the others; and the furest way, in most cases, will be to embrace that which most favours the action of the rudder,
We have, in the first book, explained several methods of describing the midship frame, which may be improved by the remarks in the second and third books.
Suppose we cannot perfuade ourselves to abandon the common practical rules, nor venture at once to go to the utmost point of perfection, yet it is to be wished, that the breadth and depth should bear but a very small proportion to the length; it is a mat. ter of great importance, and merits the utmost attention of the builders. The section of the midhip frame should be a trianzie in light frigates, but a rectangle in ships buile for burthen. In these last, the breadth is continued the same as in midships, for a considerable space, nearly the fifth part of the whole" length. The common rules are very well adapted to the building of such Thips, and want very little amendment, but are very deficient in the frigates, which begin to narrow bocb fore and aft, froin the RIR, Sept. 1765.
very very midship frame. The ships of war, as it were, keep a mean betwixt these two; they are ships of burthen, but their great weight is situated in a very inconvenient manner, their center of gravity being too near their metacenter; they must, on that accouni, and on account of carrying their metal, be broader in proportion than other ships.
The principal dimensions being established, we may form the ribbands, and so the work will be compleated. We may use the method of approximation, delivered in the XIth chapter of the first section of the first book; or conform to the tables, which we have with great pains calculated, and inserted at the end of the last section, that the pracical part inay receive all the benefit that · may accrue to it from theory.
Mr. Murray next proceeds to give an abridgment of what Duhamel has said in his second edition, on the center of gravity ; but as this part of the work cannot be understood without the figures that accompany it, we must refer the reader to the work itself, which contains many useful observations on that important subject. Our Author has concluded this part with some experiments, made, he tells us, by one of our own countrymen, whose abilities are unexceptionable. They appear, indeed, to be made, with great accuracy, and prove that we shall gain considerably by placing the midship frame before the middle, perhaps at near two thirds of the length from the after end. We could however have wished, that the ingenious experimenter had investigated the cause of this, as his reinarks on what he calls the friction of the water, seem to indicate that he does not want abilities. Perhaps these experinsents may induce some of the mathematicians to undertake the task, as it would be doing important service to their country.
The work is concluded with the method of bevelling the cant timbers by the diagonal ribbands; &c. and some observations on the mafting of fbips ; with the proportions used in England, and particularly in the royal nav.y.
Continuation of the Account of Dean Swift's Posthumous Pieces:
"See our lant Month's Review, p. 156.
Y Nour two former articles relating to these posthumous wriitings of the inimitable Dean, we have proceeded about half way through the coilection; and now we come to, i. A tract entitled “On the death of Mrs. Johnson.'-Of this lady (the very excellent Stella) we have frequently had occafion to make conlucrüble mention in our Reviews. In the account of Lord
Orrey's remarks on the life and writings of Dean Swift * we expariated pretty largely on the supposition of her being the (concealed) wife of our Author ; and also on the report of her being
wire of our humors and able on the report his sister ; and in the Review of Dr. Delany's observations on Lord Orrery's Remarks I, we likewise gave our Readers an abstract of what the observer had offered, in endeavouring to account for the Dean's mysterious conduct, in regard to a woman of such transcendent merit - Farther, in our account of Mr. Dean Swift's Essay on the Life, Writings, and Character of Dr. Jonathan Swift, we inserted some additional anecdotes + and strictures on this curious subject : to all which, we now refer our Readers, by way of introduction to the ensuing particulars concerning the charming but unfortunate Stella, written by the hand of what shall we call him-her friend, her brother, her lover, or her husband ?
• This day, being Sunday January 28th, 1727-8, about eight o'clock at night a fervant brought me a note, with an account of the death of the truelt, most virtuous, and valuable friend, that I or perhaps any other person ever was blessed with. She expired about fix in the evening of this day; and, as soon as I am left alone, which is about eleven at night, I resolve, for my own fatisfaction, to fay something of her life and cha
racter. Han · She was born at Richmond in Surrey on the thirteenth day
of March, in the year 1986. Her father was a younger brother of a good family in Nottinghamshire, her mother of a lower degree; and indeed the had litile to boast of her birth. I knew her from fix years old, and had fome share in her education, by directing what books she Mouid read, and perpetually instructing her in the principles of honour and virtue ; from which the never swerved in any one action or moment of her life. She was sickly from her childhood until about the age of fifteen : But then grew into perfet health, and was looked upon as one of the moit beautiful, graceful, and agreeable young women in London, only a little too fat. Her hair was blacker than a raven, and every feature of her face in perfection. She lived generally in the country, with a family, where the contracted an intimate friendship with another lady of more advanced years. I was then (to my mortification) settled in Ireland; and, about a year after, going to visit my friends in England, I found the was a liccle uneasy upon the death of a person on whom she had fome dependance. Her fortune, at that time, was in all not above fifteen hundred pounds, the interest of which was but a Icanty maintenance, in so dear a country, for one of her spirit.
Upon this consideration, and indeed very much for my own far tisfaction, who had few friends or acquaintance in Ireland, I prevailed with her and her dear friend and companion, the other lady *, to draw what money they had into Ireland, a great part of their fortune being in annuities upon funds. Money was then at ten per cent. in Ireland besides the advantage of turning it, and all necessaries of life at half the price. They complied with my advice, and foon after came over ; but, I happening to continue some time longer in England, they were much discouraged to live in Dublin, where they were wholly strangers. She was at that time about nineteen years old, and her person was soon distinguished. But the adventure looked so like a frolic, the censure held, for some time as if there were a secret history in such a removal ; which, however, soon blew off by her excellent conduct. She came over with her friend on the . in the year 170--; and they both lived together until this day, when death removed her from us. For some years paft, she had been visited with continual ill-health : and several times, within these two years her life was despaired of. But, for this twelve-month past, she never had a day's health ; and properly speaking, she hath been dying six months, but kept alive, almost against nature, by the generous kindness of two phyfi. cians, and the care of her friends. Thus far I writ the same night between eleven and twelve.
Never was any of her sex born with better gifts of the mind, or more improved them by reading and conversation. Yet her memory was not of the best, and was impaired in the latter years of her life. But I cannot call to mind that I ever once heard her make a wrong judgment of persons, books, or affairs. Her advice was always the best, and with the greatest freedom, mixed with the greatest decency. She had a gracefulness fomewhat more than human in every motion, word, and action, Never was so happy a conjunction of civility, freedom, eafiness and sincerity. There seemed to be a combination among all that knew her, to treat her with a dignity much beyond her rank: Yet people of all sorts were never more easy than in her company. Mr. Addison, when he was in Ireland, being introduced to her, immediately found her out; and if he had not foon after left the kingdom, assured me he would have used all endeavours to cultivate her friendship. A rude or conceited coxcomb pafled his time very ill, upon the least breach of respect; for in such a cale she had no mercy, but was sure to expose him to the contempt of the standers by ; yet in such a manner as he was aThaned to complain, and durft not resent. All of us, who had the happiness of her friendship, agreed unanimously, that, in an afiernoon or evening's conversation, she never failed before we parted of delivering the bcft thing that was said in the company.
Some, • Mrs. Dingley.