on each side of the keel, are made to run from one end of the ship to the other, and in large ships chain riveted, as previously recommended, which will greatly enhance the value of the ship. If this were done so as to give the required midship-section necessary for the security of the vessel, it would prove highly advantageous.

The Great Eastern, which is probably the strongest vessel in proportion to her size ever built, is constructed on this principle; and the designer, the late Mr. Brunel, was too sagacious an engineer to lose sight of the cellular system, developed first in the Britannia Bridge, to neglect its application to the deck as well as the hull of the monster ship.

The result of this application, with the longitud bulkheads, constitutes the enormous strength

magnificent vessel, proving the importance of the cellular system for vessels of large tonnage. It combines lightness with strength, and the double sheathing gives immense rigidity to the construction; in fact, the Great Eastern is a double ship up to the water-line. With smaller vessels, however, this system is not applicable; but a modification of it, as shown in fig. 55, may be safely adopted with advantage to both builder and owner. The exchange from the old system to the one I am urging will not call for any great sacrifice; the change I propose is a new and more scientific distribution of the material, and not any great increase of sectional area, and consequently of weight throughout the construction.

156

In the formation of the deck, it is essential, for public security, that a new principle of construction should be immediately adopted, and that the cross-beams forming the upper deck should be covered with iron stringer-plates, thickest towards the middle of the vessel, and tapering from to inch thick as they approach the stem and stern. The sectional area thus obtained, however, is short of what would be required for a vessel of the magnitude we have been considering. To secure a proportionate resisting power in the deck, we shall require the arrangement shown in fig. 55, giving an area of 750 square inches, exclusive of the hatchways, which I have estimated at 8 feet wide. This sectional area would be distributed as follows:

Thus we should have in the hull and area of security; and the vessel, so f ultimate strength, would be superior to she might be subjected at sea or on s most trying circumstances she would not breaking, and the passengers and cargo bability be secure.

In these recommendations we have no the experienced shipbuilder the details all we contend for is greater security perty, obtained by adherence to sound struction of well-ascertained truth. I these objects, I would venture to sugg improvements and additions to the n iron vessels, viz, the introduction of tw gular stringers, one on each side of

and two triangular stringers, one on each side of the vessel, as shown in fig. 55. a a is the wooden deck, under which is a platform of -inch plates, riveted to the light beams bb, which rest on the two triangular cells cc, to which they are riveted, as also to the rectangular cells dd, which run the whole length of the ship, and rest on the water-tight bulkheads, which divide the ship into eight separate compartments. These cells should be chain-riveted, and by the same means to be attached to the angle-iron of the bulkheads on which they are supported. These will diminish the span of the cells and lighten the deck-beams, which will not exceeed 15 feet in length from the cells dd to the side of the ship. It will not be necessary to go farther into detail, as the crossbeams and gusset-stays to the lower deck are of much less importance than the corresponding parts in the deck we have considered.

As respects the quality of the iron used for shipbuilding, the greatest care should be observed in the selection. Twenty to thirty shillings a ton will make all the difference between good plates and worthless ones, and no plates ought to be used which will not stand an average tensile strain of 20 tons per square inch. The better qualities of plates vary from 20 to 25 tons per square inch; but well-wrought plates, free from dross, and equal to an average test of 20 tons per square inch, will give to the vessel, if well constructed, adequate durability and strength.

It is from this material (iron) that we derive the instruments of our civilisation; our progress in useful art depends upon our knowledge of its application; ships of 400 to 700 feet in length, and bridges of equal span, could never have been attempted in its absence; in its varied forms and conditions, it supports our wonderful industry, and is the soul of our commerce. Viewing it in

this light, how important is the development of every new law and every new application which tends to secure its economical employment! and looking at our continued progress in our knowledge of its properties, and its conversion from the crude ore to its final condition in its various applications, we may say that the iron age of the world has come, nourishing a never-failing and widely-extending industry, an industry which has raised this highlyfavoured country to the position of the leader in practical science, and the pioneer of progress.

Having thus pointed out the defects and the remedies to be applied for giving increased security to iron ships, it simply remains for me to urge upon the merchants and builders in this great community the absolute necessity of adhering to the fixed and determined laws of physical truth which I have endeavoured, however imperfectly, to inculcate; but which, if carefully followed, will greatly extend our iron constructions, and render the iron ship of British manufacture triumphant on every sea.