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rescinding that order, and that we shall not only witness the introduction of iron for that service, but more particularly when steam power is employed in all and in every condition of an effective and a safe marine.

The effects of shot on iron vessels.

As respects the effects of shot upon iron vessels (a circumstance which led to the above decision on the part of the Admiralty), although at first sight alarming, they are, on more mature consideration, such as might reasonably be expected. A number of experiments were undertaken some years since at the Arsenal, Woolwich, to determine the effect of shot upon the hull of an iron vessel, and also with the view of providing means for stopping the passage of water in the event of the vessel receiving a shot below the water line. The gun used in the experiment was a 32-pounder, placed at a distance of 30 yards from the targets, and was loaded at the commencement with the full charge of 10 lbs. of powder. Subsequently, it was reduced to 8, 6, 4, 2, and 1 lbs. to produce the effect of distance in a short or long range. I assisted, at the request of the late Admiral Sir George Cockburn, at those experiments, and the results, some of which I may venture to mention, were exceedingly curious and interesting. The initial velocity of the ball, 6 inches in diameter, with a full charge of 10 lbs. of powder, is about 1,800 feet per second, and with 2 lbs. of powder about 1,000 feet.

In these experiments there were five or six targets about six feet square, composed of different thicknesses of plates, and variously arranged, so as to represent in effect as well as in appearance a portion of the side of an iron ship. Diagrams are here exhibited to represent a side view and sections of the plates and fastenings of the targets, and the effects produced by the shot as it passed through the plates, and also in three or four other

experiments, through a lining of india-rubber and cork dust, specially introduced to prevent the dispersion, and arrest the progress of the splinters as they were driven forward by the effects of the shot.

Fig. 22 represents a side view of the target with the effects of six shots at various velocities through it. Fig. 23 shows the effect of a shot with a charge of 10 lbs. of

FIG. 22.

powder through three thicknesses of -inch plates, and figs. 24 and 25 the effect of a 2 lb. and 1 lb. charge through a single 4-inch plate, with ribs of the usual construction.*

I should not be justified in going into further details on this subject at present, and must confine myself to general terms. On some future occasion I may, however, be

* See Appendix No. V.

enabled to resume the inquiry, which is one of considerable interest and of great public importance.

Whilst laying before you such information as I possess on the subject of iron ship building, it is not my intention to trench upon the province of the marine architect as respects the forms, lines, or other details required in construction. That field is already occupied by men of great experience and superior talent, and the only one to which I would more immediately direct your attention is that

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which refers to the proportion of the parts, the distribution of the material, and the equalisation of the powers of resistance to strain in the different parts and positions of the structure. These are considerations which, in a greater or less degree, affect almost every description of mechanical construction, and we cannot be far wrong if on this occasion we endeavour to supply such experimental knowledge as we possess to the improvement of this important art.

If we study the art of construction as exhibited in the law of nature, we shall find endless varieties of form. In

the animal and vegetable kingdoms there is no waste of material. Every animal and every plant is adapted to its purpose, its organisation is perfect in every respect; every joint, muscle, and fibre is suited to the work it has to perform, and the utmost harmony in proportion, beauty of design, as well as economy of material, is discernible in every construction that emanates from the hand of nature's Architect. In that school we are sure to learn under the tuition of that great Teacher in every department of art, and by a careful study of those laws which open upon us at every page, we can scarcely fail to apply them to some good and useful purpose.

With such examples before us, and with such a wide and wonderful range of objects, why should we commit blunders, and hesitate when we should analyse and investigate? There is no mechanism so intricate but we find its compeer in nature, and where we may find a rule for our guidance. We have only, therefore, to study Nature in her varied forms and conditions to arrive at sound conclusions either as regards the examples that are set before us, or the approximation to laws which govern all constructions.

Our present object is, however, limited to the inquiry into the laws which guide the experienced ship-builder in the prosecution of his art: it will be proper in the first instance to ascertain the nature and strength of the material he may choose to employ, in order to show in what way it would be disposed to produce at a minimum cost the greatest possible effect. For these objects I am fortunate in having before me a long series of experiments which I made for the same object more than ten years ago.* These facts are given in Appendix I., but to save trouble in the reference I have considered it necessary to lay before you the following short abstracts, which I trust

* See Philosophical Transactions, Part II, 1850, and Appendix No. I.

may prove equally beneficial in this as they have been in other constructions.

In the resistance of wrought-iron plates we have in these experiments, which were made on five different sorts of iron, the tensile strengths in tons per square inch as follows:

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These results give a mean power of resistance of nearly 23 tons per square inch. And the ratio 22.5: 23, gives about 4th in favour of those torn across the fibre.

In following up similar investigations on timber, I found, according to Professor Barlow, of Woolwich, that the cohesive strength of different kinds of hard wood were

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Assuming Mr. Barlow to be correct, and taking the mean strength of iron plates as given in the experiments at 49,656 lbs. to the square inch, or say 50,000 lbs., we have the comparison between wood and iron in the following ratios of resistance to a tensile strain :—

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