{ "id": "juan-examen-maritimo-1771", "type": "entity", "name": "Jorge Juan, Examen marítimo theórico práctico (Madrid, 1771)", "summary": "A Spanish naval officer set out to take shipbuilding out of the hands of carpenters and put it on mechanics. The 1771 treatise reviews the European literature by name, rejects Bouguer's masting rules and the pendulum theory of rolling, and builds a theory of fluid resistance — then prints, in a scholium, the objection that might overturn it. Its 1793 Spanish editor records both the Paris-privileged French translation of 1783 and the slips he found in the text.", "locale": "en", "tags": [ "science", "navigation", "shipbuilding", "mechanics", "hydrodynamics", "books", "eighteenth-century", "madrid" ], "relations": [ { "rel": "related", "target": "jorge-juan" }, { "rel": "related", "target": "antonio-de-ulloa-platinum" }, { "rel": "related", "target": "noticias-secretas-de-america" }, { "rel": "related", "target": "spanish-navigation-manuals-in-england" }, { "rel": "related", "target": "garcia-de-palacio-instruccion-nautica-1587" }, { "rel": "related", "target": "malaspina-expedition" } ], "questions": [ "What is Jorge Juan's Examen marítimo of 1771?", "What did Jorge Juan say was wrong with Bouguer's theory of the ship?", "Was the Examen marítimo translated into French?", "How did Jorge Juan treat the resistance of fluids?", "Did anyone find errors in the Examen marítimo?" ], "claims": [ { "id": "c1", "text": "The title page reads \"EXAMEN MARITIMO Theórico Práctico, ó TRATADO DE MECHANICA aplicado á la CONSTRUCCION, CONOCIMIENTO Y MANEJO DE LOS NAVIOS y demas Embarcaciones. Por D. JORGE JUAN, Comendador de Aliaga en la Orden de San Juan, Xefe de Esquadra de la Real Armada, Capitan de la Compañía de Guardias Marinas, de la Real Sociedad de Londres, y de la Academia Real de Berlin. TOMO PRIMERO. EN MADRID: En la Imprenta de D. Francisco Manuel de Mena, Calle de las Carretas. M.DCC.LXXI. Con permiso Superior.\" The author's fellowships of the Royal Society and of the Berlin academy are printed on the title page of his own book.", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.95 }, { "id": "c2", "text": "The prologue opens with the diagnosis that gives the book its purpose. Except for the short principles on which pilotage rests, the seaman's instruction had until very recently been held to be purely practical: the building of ships and their handling \"ha estado siempre en manos de unos casi meros Carpinteros, y de otros puramente trabajadores ú operarios: ninguna dependencia se creyó que tuviesen de la Matemática, sin embargo de no ser el todo sino pura Mecánica: Ciencia, quizás, la mas dificil y mas intrincada del mundo\". Jorge Juan then explains the neglect rather than merely deploring it - the seaman occupied with risk and fatigue has no quiet for so long a study, and the studious man does not accommodate himself to the other's toil, and the two are what teach with ease the results that theory alone could hardly discover. This text is quoted from the prologue as reprinted in the second edition of 1793.", "sources": [ "juan-examen-maritimo-1793" ], "confidence": 0.9 }, { "id": "c3", "text": "The prologue is a literature review with names, dates and section numbers. Page XIII cites \"A Treatise of fluxions\" published in 1742 by \"el gran Geómetra Colin Mac Laurin, Profesor de Mathemáticas en la Universidad de Edimburgo, y Miembro de la Real Sociedad de Londres\", where at volume 2 §922 the problem of the angles the sails should make with the keel and with the wind is also solved, agreeing with the solution given by Johann Bernoulli. Jorge Juan's objection is to the assumptions, not the geometry: the principles are \"que la velocidad del viento es infinita, respecto á la del Navío, y la deriva nula\", and without those and without \"los falsos supuestos de las resistencias\" the perfect solution would have been had.", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.9 }, { "id": "c4", "text": "On the same page the credit to the leading French authority is given in full before the criticism. Bouguer, \"el mismo que en el año 1727 nos dió la Mature des Vaisseaux\", published in 1746 his second marine work, the \"Traité du Navire, de sa construccion & de ses mouvemens\"; its extent, the prolix examination of the diversity of matters treated, and the soundness of its geometric solutions, almost reduced to the reach of beginners, \"le dieron el honor que merecia en toda la Europa\". The reservation follows in the same sentence and is about practice rather than mathematics. Jorge Juan's own statement of what remained to be done is that all these works reduce to \"un limitado número de proposiciones sueltas: faltaba la recopilacion de todas ellas, la correccion de las erradas, y la adiccion de muchas que aun no se habian ofrecido.\"", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.9 }, { "id": "c5", "text": "The masting rules are rejected against experience. Page XXIX records two causes that carry the axis of the motive force much further aft than the received account allows - the curvature of the sail and the heel of the ship - and notes that these alterations are not constant but vary with the force of the wind, the figure of the sails and the ship's stiffness. Had the masts been placed as the theory advised, \"hubiera sido imposible el govierno, y muchísimo peor si se le hubieran dado las medidas que Mr. Bouguer ha pretendido.\"", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.9 }, { "id": "c6", "text": "The same page attacks the theory of rolling and pitching at its foundation. In the received account no action is considered beyond that resulting from an oscillatory motion, the ship being supposed a pendulum, so that all its rolls and pitches must take the same time and no relation appears between the roll and the wave, \"sin embargo que es su verdadera causa\". If the theory is referred instead to the second or third rolls, supposed free of the same wave, Jorge Juan asks who can doubt that the first are the most effective; and since no roll can be completed without the wave having made its transit, and waves do not pass in equal times but in very different ones according to their magnitudes, \"se hace de admirar como se ha podido creer y admitir tan generalmente iguales errores.\"", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.9 }, { "id": "c7", "text": "The theory of resistances is where the book states its own principle, and where it states the objection to it. The scholium on page 269 recalls that the force with which the fluid acts against a differential-differential of surface has been set proportional to the square of a quantity, \"y el principio que nos conduxo fue, haber deducido que la velocidad con que saliera el fluido por la misma diferencio- diferencial, si tubiera libre pasage\" was that quantity - the resistance derived from an efflux velocity rather than assumed. The algebraic expressions are not transcribed here because the setting could not be read with certainty from the scan.", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.8 }, { "id": "c8", "text": "The objection is the author's own and he prints it before answering it. Notwithstanding the solidity of that foundation, \"puede ofrecerse el reparo de que quizas seria igualmente sólido suponer, que el peso que debe sufrir la diferencio-diferencial, no ha de ser sino el de la coluna del fluido incumbente\", the height of the swelling or cavity being taken into account. Jorge Juan works the alternative through to a resistance that must be halved when the parallelepiped is only a plane, and then concedes what it has going for it: \"Esta determinacion, que tanto se conforma con la opinion general, y lo que es mas con las experiencias que nos dá M. Mariotte en el tercer discurso de la parte segunda de su Tratado del movimiento de las aguas, pudiera muy bien equiponderar, ó quizas inducirnos á suprimir nuestra theórica; pero el cúmulo de experiencias que la acreditan\" - the answer he gives is a body of experiment, not an assertion of authority.", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.9 }, { "id": "c9", "text": "The table of contents shows that the doubt is structural and not an aside. The chapters on horizontal resistances run from finding the resistance suffered by a body moved in the fluid, through the rectangular parallelepiped, to \"Dudas sobre la theórica de las resistencias: examen de las experiencias, y errores en estas\" at page 269, and on to cylinders, spheres and bodies of any shape. Chapter 6 treats the vertical resistances suffered by bodies moved in fluids, including the different vertical resistance in the two cases of moving upwards or downwards; chapter 7 treats how the unlevelling of the fluid at one surface alters the force and resistance suffered by others.", "sources": [ "juan-examen-maritimo-1771" ], "confidence": 0.9 }, { "id": "c10", "text": "The 1793 second edition opens with an editor's Introduccion that records the book's European circulation. It asserts that \"En toda Europa se han dado repetidas muestras del aprecio que hacen los Sabios del Exâmen Marítimo\" and gives one concrete channel: \"M. Leveque, Hidrógrafo y Profesor Real de Matemáticas en Nantes, publicó en 1783 una traduccion francesa de todo el tratado, enriquecido con un breve comentario\", printed under the privilege of the Académie Royale des Sciences of Paris, from which articles relating to marine were taken into the new French encyclopaedia arranged by subject. The bibliographical particulars are carried here at moderate confidence because the only witness opened for them is an admiring Spanish edition of a Spanish author.", "sources": [ "juan-examen-maritimo-1793" ], "confidence": 0.8 }, { "id": "c11", "text": "The same editor supplies the counterweight, and it is the most useful thing on the page. Having undertaken to explain the first two books of the Exâmen Marítimo in a course of higher mathematics that ended in February 1789, he carefully went over the author's calculations and metaphysical considerations and \"encontré algunos descuidos que no se nos advierten en la traduccion francesa\" - some slips, not flagged in the French translation. He extended himself to new applications, read a discourse on these first essays at the opening of the certámenes, and had it printed shortly afterwards at Murcia. The notes he added are indexed by chapter and article in the same edition.", "sources": [ "juan-examen-maritimo-1793" ], "confidence": 0.85 }, { "id": "c12", "text": "Where the editor thinks the originality lies is his opinion and is carried as such. He holds that the part the title announces - construction, knowledge and handling of vessels, discharged completely in the second volume of the first edition - is without doubt the most interesting, but that in the principles of the mechanics of solids contained in the first book, \"la teoría de la percusion, la de la friccion, y la de las máquinas tienen un mérito superior, y son casi enteramente suyas\", even the known matters being treated with a geometric elegance characteristic of an original genius. No independent assessment is cited here for that judgement.", "sources": [ "juan-examen-maritimo-1793" ], "confidence": 0.7 }, { "id": "c13", "text": "The limits of this reading should be stated. Five leaves of the 1771 first volume were opened - the title page, prologue pages XIII and XXIX, the contents leaf listing chapters 5 to 7, and printed page 269 - together with three leaves of the 1793 second edition. The second volume of 1771, which carries the application to construction and handling, was not opened. Nothing in these sheets shows what Spanish or American dockyards did with the book, and no claim about its effect on ships actually built is made here.", "sources": [ "juan-examen-maritimo-1771", "juan-examen-maritimo-1793" ], "confidence": 0.9 } ], "takeaways": [], "faqs": [], "evidence_tier": "primary", "evidence": { "level": "industry_observation", "source_types": [ "paper" ] }, "moat_flag": false, "winning_edge": "English-language accounts of Jorge Juan almost always stop at the Quito arc measurement and the Noticias secretas, and where the Examen marítimo is mentioned it is as a title in a list. This object opens the 1771 sheets and gives page numbers, so the book can be read as an argument rather than cited as a monument. It shows the target named - shipbuilding left \"en manos de unos casi meros Carpinteros\" while being nothing but mechanics - and it shows the method: Maclaurin's Treatise of Fluxions cited to volume and section, Bernoulli's solution accepted and its premises rejected, Bouguer credited with the honour he had in all Europe on one page and his masting measures called worse than useless on another. Most of all it prints the page where the author argues against himself: the scholium at 269 states the rival hypothesis that \"pudiera muy bien equiponderar, ó quizas inducirnos á suprimir nuestra theórica\", concedes that it agrees with general opinion and with Mariotte's experiments, and answers it with a body of experiment. The reception and the errata come from the same quarter and are kept apart: the 1793 Spanish editor is the witness both for Lévêque's 1783 translation printed under Paris academy privilege and for the \"algunos descuidos\" he found in Jorge Juan's own calculations, and his praise is labelled as opinion.", "confidence": 0.85, "last_verified": "2026-08-15", "canonical_url": "https://hispanic-legacy.com/k/juan-examen-maritimo-1771", "api_url": "https://hispanic-legacy.com/api/k/juan-examen-maritimo-1771.json", "jsonld": { "@context": "https://schema.org", "name": "Jorge Juan, Examen marítimo theórico práctico (Madrid, 1771)", "description": "A Spanish naval officer set out to take shipbuilding out of the hands of carpenters and put it on mechanics. The 1771 treatise reviews the European literature by name, rejects Bouguer's masting rules and the pendulum theory of rolling, and builds a theory of fluid resistance — then prints, in a scholium, the objection that might overturn it. Its 1793 Spanish editor records both the Paris-privileged French translation of 1783 and the slips he found in the text.", "url": "https://hispanic-legacy.com/k/juan-examen-maritimo-1771", "license": "https://spdx.org/licenses/CC-BY-4.0.html", "dateModified": "2026-08-15", "citation": [ { "@type": "CreativeWork", "name": "Examen maritimo theórico práctico, ó Tratado de mechanica aplicado á la construccion, conocimiento y manejo de los navios y demas embarcaciones. Tomo primero", "url": "https://books.google.com/books?id=94BfXaScDrEC&pg=PR1" }, { "@type": "CreativeWork", "name": "Examen maritimo teórico práctico ó Tratado de mecánica aplicado á la construccion, conocimiento y manejo de los navíos y demás embarcaciones (second edition, with the editor's Introduccion and added notes)", "url": "https://books.google.com/books?id=DAqnCCafCesC&pg=PP5" } ], "@type": "Article", "headline": "Jorge Juan, Examen marítimo theórico práctico (Madrid, 1771)" } }