The advantages to be derived from the circular stern may be principally reduced to the three follow ing heads: Firs/, A considerable addition to the strength of the ship.
Secondly, Safety to the people employed, both from the effects of a sea striking the stern, and from shot fired by the enemy.
Thirdly. The additional means afforded for attack and defence.
The insufficiency in point of strength of the old method of constructiong the sterns, is proved in Sir Robert Seppings's letter to the first Lord of the Ad miralty, by his having given from various official re ports, eighty-Mne instances in ships of' the line, and eighty in frigates, of the great weakness of that part of the ship. These instances of defect being derivec: from the reports of officers of intelligence and dis tinction, employed in services of the most diversified and trying kind for the long period of a quarter of a century,t necessarily stamps the body of information which Sir Robert has collected in the letter alluded to, with the utmost importance and value. The defect in the old square form being thus rendered so notorious, led to the consideration of the best mode of remedy ing it; and the acknowledged strength of the round bow, a part subjected to the action of far greater strains than the stern, naturally led to the considera tion of fortifying the latter by the same mode of tim bering, and from this arose the circular stern. More over, before the application of this system, the new mode of shipbuilding so successfully introduced by Sir Robert Seppings. might be truly said to be incom plete, for the shelf pieces and water ways, as well as all the planking above the wing transom, which may be denominated internal and external hoops, were cut off, and hence left the stern the only weak part in the ship. " In ships with square F terns," Mr. Haney has remarked, '• the application of the diagonal system of trusses does not produce its maximum effect, nor is the continuity of the shell pieces preserved, since the most abrupt termination of them takes place at the quar ters, a difficulty entirely removed in the circular form by the happy introduction of the ekeing, and affording a perfect illustration of the term 'internal hoop,' so appropriately applied to them by Sir Robert Sep pings." "It is the mode of timbering those sterns," as Air. Knowles with equal propriety observes. and a continuity of the internal and external planking that constitute their strength. and establiskes on a firm and unquestionable basis, their importance and value." These remarks will be confirmed by an inspection of Figs. 1, 2, 3, and 4, Plate CCCCXCVI. Figs. 1 and 3, the former of which represents an internal right aft view of a square stern, and the latter a plan representing the mode of -connecting a stern of the same kind, with its sides. it will be perceived that the
strength of this form of the stern depends in a very great measure on the iron knees at the quarters or angles, which are bolted to the deck transom A, and through the side timbers of the vessel. Now any frac ture or defect in the iron knee, will of course weaken the stern, and contribute to all the defects before al luded to, and which have led to the introduction of the new form. It will also be perceived by inspecting both figures, but particularly the former, that none of ti•e water ways C. C. C, C, or shelf pieces D, ll, D, °I), contribute in any degree to bind together the fab ric of the stern, or to add in any manner to its strength; nor do any parts of the stern frame, excepting the transoms, tend to keep the sides of the ship together, and which is only done by means of the iron knees before alluded to. and the dowels. denoted by the dot ted circles at their extremities. On the wing transom E. moreover, rests the Whole fabric of the stern, every upright timber as B, Ii .. . B, li, stepping or rest ing thereon. Now, we will venture to say, that in the whole history of c,nst•octi,c carpentry, a example can scarcely be foand than this of defective and bad combination; of timbers disposed at right angles to each other,—the worst possible position, where oblique strains are to be endured; without a diagonal timber to prevent even the well-known de rangement of form arising from raking; trusting to knees and bolts, ill adapted, from their positions, to resist those derangements of form which most arise from the shocks that so ponderous a fabric must re ceive from the terrible element with which it has to contend, and with the decays also and weaknesses that time, the great innovator of mechanical as well as moral systems, is so incessantly producing. Can it be a matter of wonder, therefore, that such an ill-con t•ived frame as the stern of a ship constructed on the old form, should, in the technical but expressive lan guage of the shipwright, "work:" that the whole hotly of the poop should sometimes move pow side, to side, resting, as the entire fabric of the stern does, on a single timber, massy, of course, but with its strength ill applied, and ill connected with the sides of the ship, the proper and perfect union of which should be inseparable? But if we turn to the diagrams illustrative of the round stern, we shall discover no such mechanical anomalies as disgrace the ancient form. Every part will be lOund to be disposed with some reference to the laws that ought at all times to influence mechan ical structures. To prove this in its fullest sense, we need only compare Fig. 2. with Fig. I. and Fig. 4. with Fig. 3.