SAINT-VENANT, Adhémar Jean Claude Barré de.

Du Roulis sur Mer houleuse. Calculé en ayant Égard à l'Effet retardateur produit par la Résistance de l'Eau.

66, [1] pp. 8vo, orig. blue printed wrappers (frayed, punched for a 3-hole binder, each leaf loose). Paris: Dunod & Gauthier-Villars, 1871. First separate edition, a separately paginated “Extrait des Memoires de la Société des Sciences naturelles de Cherbourg, T. XVI.” “In this paper, St. Venant discusses waves on rough seas, calculating them with regard to the retarding effect produced by the resistance of the water... “St. Venant’s purpose in these researches is to show whatever the known form on the surface of the wave might be, that the integration of the wave in a non-resistant water can be integrated. From this form, to take the integral, relative to the troichoidal form, even in taking, as proposed by Bertin in a suite to his work of 1869, for the variable direction of the resulting fluid pressure, not precisely the normal at the surface of the wave in the environment of the part occupied by the vessel, but an average between the directions of the normals at the curve of level, also troichoidal, traversing the vessel at a certain depth, for example, that at the center of the keel... “Finally, to take account analytically of the effect of resistances opposed by the water, and up to a certain point by the air, to the movement of waves on vessels; an effect which is easily calculated for the case of a calm sea, in simply adapting to the question the solution that Poisson gave of the movement of a pendulum in an environment which resisted it proportionally either to its speed or to the square of that speed relative to the water. The evaluation of the same effect for the case of a rolling sea is found comprised in the integral of the equation of the movement, which one can again obtain in completed form when one supposes the resistance proportional to the simple speed, a supposition which, after a great number of hydraulic facts, appeared realized in the low movements, as those that the builders of vessels look for, above all today, to obtain for their waves.”–Roberts & Trent, Bibliotheca Mechanica, pp. 288-89. Not at all a good copy, but really rare. Preserved in a black morocco-backed box. Ex Bibliotheca Mechanica.

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