APPENDIX. I. An Experimental Inquiry into the Strength of Wrought-Iron Plates and their Riveted Joints as applied to Ship Building and Vessels exposed to severe Strains.* THE EXPERIMENTS herein recorded were instituted early in the spring of 1838, and before the close of the following winter most of them had been completed; owing, however, to a long series of professional engagements, they have stood over (with the exception of some additions made in the following year) to the present time. The object of the inquiry was twofoldfirst, to ascertain by direct experiment the strength of wroughtiron plates and their riveted joints in their application as materials for ship building; and, secondly, to determine their relative value when used as a substitute for wood. On these two points it cannot be expected that our knowledge should be far advanced, as a very few years have elapsed since it was asserted that iron, from its high specific gravity, was not calculated for such a purpose, and that the greatest risk was likely to be incurred in attempting to construct vessels of what was then considered a doubtful material. Time has, however, proved the fallacy of these views, and I hope, in the following experiments, to show that the iron ship, when properly constructed, is not only more buoyant, but safer and more durable than vessels built of the strongest English oak. * Philosophical Transactions, Part II. 1850, p. 677. At the commencement of the experiments I felt desirous of conducting them upon a scale of such magnitude as would supply sound practical data, and at the same time establish a series of results calculated to ensure confidence as well as economy in the use of the material. My views were ably carried out by Mr. Hodgkinson, who conducted the experiments under my direction, and from whom I received valuable assistance. In conducting the investigation, I found it necessary to divide the subject into four distinct parts : 1st. The strength of plates when torn asunder by a direct tensile strain in the direction of the fibre, and when torn asunder across it. 2ndly. On the strength of the joints of plates when united by rivets as compared with the plates themselves. 3rdly. On the resistance of plates to the force of compression, whether applied by a dead weight or by impact. And lastly. On the strength and value of wrought-iron frames and ribs as applied to ships and other vessels.* PART I. At the commencement of iron ship building, in which I took * Several important facts and improvements in the construction of iron ships have been ascertained since my experiments were made, but I apprehend none of them have tended in the least degree to diminish their value. Nor have they, to the best of my knowledge, been superseded by others of a more elaborate or more decisive character. It is true that a series of interesting and important experiments have been made at the instance of the Admiralty on the effect of shot upon the sides of iron ships. At some of these experiments I had the honour to be present, and witnessed some curious and unexpected results. The first series was conducted at the Arsenal, Woolwich, and subsequently others were made at Portsmouth. Both were important as respects the effect of shot upon wrought-iron plates, with enlarged and diminished charges of powder and at different velocities, but discouraging as regards the use of iron in the construction of ships of war. These experiments, however interesting in themselves, do not appear to be conclusive; and it is to be hoped that the apparent danger, indicated by the experiments, may yet be overcome, and the superiority as well as the greater security of the iron ship fully established. enter upon an active part, the absence of acknowledged facts relative, to the strength and varied conditions under which the material was applied, was the principal reason which induced me to this inquiry. I have extended the investigation into the best methods of riveting, and the proportional strength of rivets, joints, &c., as compared with the plates and the uses for which they are intended. The latter is a practical and highly important inquiry, as great difference of opinion exists, amongst engineers and others, as to the form, strength, and proportions of rivets, and the joints of which they form an essential part. I therefore considered an experimental investigation much wanted, not only on account of its important practical bearing, but, what was probably of equal value, in order to remove existing discrepancies, and to establish a sounder principle of construction founded upon the unerring basis of experiment. From these considerations I bestowed increased attention upon the inquiry, and endeavoured to render it practically useful. Before detailing the experiments, it may be necessary to describe the apparatus by which the results were obtained. The annexed drawings, Plate I., represent a side and end view of the apparatus used in the experiments. The large lever A was made of malleable iron, and was fixed to the lower cross beam B (fig. 1) by a strong bolt O, which passed through it at B. At the top end of this bolt, a preparation was made to receive the end of the lever, and by means of the screw-nut at a, the lever A was raised or lowered to suit the length of the plates to be experimented upon. Upon the top side of the beam, and under the gable wall of a building five stories high, were placed two cast-iron columns, D, D, which retained the beam B in its place, and prevented it from rising when the lever was heavily loaded during the experiment. The frame E guided the end of the lever and the weight W, and close to the fulcrum were placed two wooden standards, F, F, on which were fixed the castiron saddles receiving the cross bar G, from which the plates to be experimented upon were suspended. These plates were nearly all of the same form, as shown at H, and were made narrower in the middle to ensure fracture in that part; the ends, as at b, b, had plates riveted to them on both sides, in order to |