63 



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 1'Oiseau. 



Having cited these and other instances to prove that Mr. Sep- 

 pings's principle is not new, at the same time allowing that the 

 merit of rendering its utility probable, and of overcoming many diffi- 

 culties in its execution, is due to that gentleman, the author pro- 

 ceeds 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 di- 

 minish the fastness of sailing, and to increase the difficulty of per- 

 forming evolutions, especially with the sails. As vessels, therefore, 

 must inevitably suffer by this effect of arching, any method of dimi- 

 nishing that tendency must be valuable. M. Dupin suggests a me- 

 thod 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 Philo- 

 sophical 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. 



On a new Fulminating Platinum. By Edmund Davy, Esq. Professor 

 of Chemistry, and Secretary to the Cork Institution. Communicated 

 by Sir Humphry Davy, LL.D. F.R.S. V.P.R.I. Read February 1 3, 

 1817. [Phil. Trans. 1817, p. 136.] 



After pointing out certain analogies between gold and platinum, 

 which rendered it probable that the latter metal would afford a ful- 

 minating compound similar to that obtained from the former, Mr. 



