Page:Proceedings of the Royal Society of London Vol 2.djvu/95

Rh navy, on account of its expense, of its diminishing the capacity of the hold, and of the erroneous notion that the longitudinal length of the ship was diminished by the obliquity of the ceiling. In 1755, the Academy of Sciences rewarded M. Chauchot, a naval engineer, for the suggestion of employing oblique for transverse riders; and in 1772, M. Clairon des Lauriers employed diagonal strengtheners in the construction of the frigate l'Oiseau.

Having cited these and other instances to prove that Mr. Seppings's principle is not new, at the same time allowing that the merit of rendering its utility probable, and of overcoming many difficulties in its execution, is due to that gentleman, the author proceeds more particularly to inquire how far it contributes to strengthen the vessel, so as to enable it to oppose changes of form from the action of external powers. If every elementary part of the vessel rested immediately on the sea, it would displace its weight of water, and would only be submitted to the slight pressure of the fluid. But as only a part of the external surface of the vessel is in contact with the water, this part is called upon to support a degree of pressure of the fluid capable of counteracting the weight of the whole mass. Hence the vessel becomes convex or arched, the curve extending from the head to the stern; but as this bending is not of constant magnitude, it is evident that, in order to apportion the resistance adequately, the strength must be made greatest where there is the greatest strain. The author furnishes some new theorems for the determination of these points, and thence concludes that the point of greatest curvature lies between the quarter-deck and forecastle, across the gangways, and much nearer the head of the ship than is commonly supposed; and that the effect of the arching is to diminish the fastness of sailing, and to increase the difficulty of performing evolutions, especially with the sails. As vessels, therefore, must inevitably suffer by this effect of arching, any method of diminishing that tendency must be valuable. M. Dupin suggests a method by which it might be ascertained whether Mr. Seppings's plan is calculated to diminish the tendency of vessels to arch; upon which subject he deems Mr. Seppings's experiments, detailed in the Philosophical Transactions, as unsatisfactory. This method, however, has not hitherto been tried, and the question, consequently, cannot be decided upon. In the meantime, says the author, there is every reason to suppose that it would prove favourable to Mr. Seppings's plan.

After pointing out certain analogies between gold and platinum, which rendered it probable that the latter metal would afford a fulminating compound similar to that obtained from the former, Mr.