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The PRESIDENT and Council of the ROYAL SOCIETY ad. judged the Medal on Sir GODFREY COPLEY's Donation, for the year 1817, to CAPTAIN HENRY KATER, F. R. S. for his Experiments on the Pendulum.

And they adjudged the Gold and Silver Medals, on the Donation of BENJAMIN Count of RUMFORD, to Sir HUMPHRY Davy, LL.D. F. R. S. for his Papers on Combustion and Flame, published in the last Volume of the Philosophical Transactions.

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I. On the great strength given to Ships of War by the application

of Diagonal Braces. By Robert Seppings, Esq. F. R. S.

Read November 27, 1817.


INCE the time that I first suggested the principle of applying a diagonal frame-work to ships of war, which was first partially and successfully adopted in the Kent, a seventyfour gun ship, in the year 1805, my mind has been conti-. nually and anxiously turned to this important subject; and it was not until the utility of the experiment had been fully established in the opinion of most naval officers, that I ventured to present to the Royal Society, a paper on the application of this well known principle to the construction of large ships of war, but which, as far as my knowledge extends, never had before that time been so applied, either theoretically or practically, in this, or any other maritime country; and I am well assured, that no such application, or suggestion, appears in any of the Continental writers on naval architecture. I merely mention this, because it has been pretty broadly insinuated, that the idea was borrowed from the French. The propriety of a different disposition of MDCCCXVIII.


the materials entering into the construction of a ship, has at different times, for more than a century past, been suggested by English ship-builders; and partial alterations have, in consequence, been introduced; but no one, that I am aware of, has at any time proposed the system of a diagonal trussed frame. If I have received any assistance in the progress of this new system, now universally adopted in the British navy, it was from the plans and drawings of the celebrated bridge of Schaffhausen, and from no other source.

The extensive application of this principle to no less than thirty-eight sail of the line, and thirty frigates, might perhaps be conclusive as to the advantages expected to be derived from the new system ; but as the Royal Society did me the honour to introduce my account of that system into their Transactions, at an early period of its adoption, I am led to hope that the result of a practical experiment, made with a view of proving the correctness of the principle, may not be deemed an improper or an uninteresting corollary to

paper. In the early part of this year (1817) the Justitia, an old Danish seventy-four gun ship, was ordered to be broken up on account of her defective state; and having observed her to be considerably arched, or hogged, as it is usually termed, I determined, notwithstanding her age and defective state, to apply the trussing principle to a certain extent, with a view to observe what effect it would produce on a fabric reduced to so weak and shaken a condition.

The officers of the yard were directed to place sights on the lower and upper gun-decks, prior to her being taken into the dock; and to ascertain, when she grounded on the


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