ship of 3,000 tons, would be of great service, especially at night, in providing crew with pure air, and the ventilation would immensely increase the durability of the vessel.'

'Vessels constructed as described would combine all the good qualities of both iron and wooden vessels, and would, in some respects, be much superior to either. They would have the plating, frame, beams, stringers, keelsons, bulkheads, platforms, &c., of an iron vessel, capable of being made of any required strength, and the wooden planking, bolted to firmly fastened timbers, would form a cellular construction adding strength quite equal to that of a similar weight of iron. It would not be necessary to increase the scantling of wooden frame and planking in proportion to tonnage, and a vessel of 4,000 tons would be about the same weight as an iron vessel of same strength and size. The weight of vessels of the smaller class would range about a medium between that of iron and wooden vessels. Fig. 46 shows an arrangement for decreasing materially the weight of iron and wooden framing, without much reduction of strength; as teak, weight for weight, is treble the strength of iron, and a plank bent in one length perpendicularly between frames, and well fastened with screw bolts to outer planking, would be an economical application of material, and give a good result.

"The after-end of these vessels could be made of any strength required to withstand the vibration of screw shaft by means of bulkheads, stringers, platforms, &c.

They would be incomparably safer, if stranded, than any vessels ever before built, in consequence of having wooden keel, planking, and floorings, to withstand the first shock of getting on shore, and the subsequent chafing, thus possessing all that contributes to the safety of a wooden ship, and having in addition a water-tight iron skin, with bulkheads, platforms, &c., and iron frames fitted outside, which, together with wooden frame, would have a tendency to push up iron ceiling, and prevent its being perforated. The iron portions of the structure of these vessels would last for an indefinite period, as they could be thoroughly prevented from oxidation by paint, cement, or bituminous coating, and would be entirely free from the injurious influence of the copper sheathing, as the leakage would pass down the inner surface of outside planking to water

spaces between the floors, without coming in contact with iron, and be pumped out by centre or bilge pumps; while the wooden portions of structure (if upper works were composed of teak) would, under the influence of currents of pure air and the absence of deleterious gases, probably last for a hundred years.

The system of construction described is specially applicable to vessels of war, as it enables any required amount of strength to be given to the structure, and the iron ceiling, with frames outside, is eminently suitable for assisting in the formation of a shot-resisting broadside.'

Figs. 43, 44, 45, and 46, show the sections of a composite vessel of about 2,500 tons register.

Fig. 43. Horizontal section of broadside.
Fig. 44. Perpendicular section of do., at x.

Fig. 45. Transverse section of keel, keelson, &c.

Fig. 46. Horizontal section of a broadside, showing mode of increasing frame spacing, when considered desirable.

a, a, a, a, figs. 43, 44, 45 and 46. Outer wooden planking, 4 inches thick, fastened to wooden frame, with screw treenails, or brass bolts, 12 inches long.

b, b, b, figs. 43, 44, and 46. Frame timbers, sided 8 inches and moulded 9 inches, inserted between, and bolted to angle-iron frames with galvanised iron screw bolts about 16 inches apart.

c, fig. 45. Wooden flooring sided 11 inches at throat, 8 inches at ends, moulded 18 inches at throat, 12 inches at ends, and inserted between angle-iron frames.

d, d, d, d, figs. 43, 44, 45, 46. Angle-iron frames, 5 inches x 3 inches x inch, riveted all round to outside of iron ceiling.

e, e, e, e, figs. 43, 44, 45 and 46. Iron ceiling, 7-inch thick, united all round at bottom and ends of vessel, and made thoroughly water-tight, forming a complete inner skin of iron.

ƒ, f, figs. 44 and 45. Liners, filling clinker spaces of ceiling, in wake of iron frames. g, fig. 45. Box keelson, 18 inches x 33 inches.

h, fig. 45. Ventilation aperture through bottom of box keelson into space between floorings.

i, fig. 45. Stiffening plate, to be fitted on each side of wooden floors, and riveted to angle-iron frames to give transverse strength. If space between frames were increased, floors could be sided larger at throat, and stiffening plates would not be requisite; or iron floorings could be introduced instead of iron ceiling.

j,j, fig. 45. Limber holes.

k, fig. 45. Main keel.

7, fig. 45. False keel.

m, m, m, m, figs. 43, 44, 45 and 46. Fore-and-aft galvanised iron screw bolts. n, n, n, n, figs. 43, 44, 45 and 46. Screw treenails.

0, 0, 0, 0, figs. 43, 44, 45 and 46. Brass bolts.

P, P, fig. 46. Perpendicular planks, 10 inches × 3 inches, bent in one length from keel upwards, between frames, and fastened to outer planking with brass screw bolts.

The iron portion of the structure, according to Mr. M'Laine, 'would be first finished complete and lightened, perhaps leaving each alternate iron frame loose, to facilitate the fitting of a wooden frame. All the iron surface in frame spaces to be carefully cemented before working on the outer planking, though there would be little tendency to oxidation, owing to the ventilation currents through frame spaces, and not much risk of excessive leakage, as the vessel could be made so strong, that if once tight it would be likely to remain so.'

24. We have given increased space to Mr. M'Laine's principle of construction, in his own words, because it probably gives the best combination of wood and iron as applied to the construction of ships. We, however, consider it inferior to, and more expensive than, the iron vessel with double bottom; and as this may ultimately prove correct, we give a further detailed description of the latter system of construction at Chap. XI.

In this investigation, we have not denied that vessels sheathed with timber and copper-fastened are superior to those of iron as regards fouling and the adhesion of molluscs and marine vegetation to their bottoms. These are difficulties which every new system of construction has to contend with; but it does not follow that some effectual remedy may not be in reserve for correcting this evil. The necessity of the case may, in all probability, bring the remedy; and we have yet to discover some chemical or electrical process by which we are to discharge or, what is decidedly preferable, prevent the adhesion of animal and vegetable life to the bottoms of iron-plated vessels. Under the impression that means will be obtained for remedying this inconvenience, we can see no reason for abandoning the iron construction. On the contrary, we have neither hesitation nor misgiving in adhering to the superior merits of iron, and, even supposing that no further progress is made for the prevention of fouling, iron for the construction of ships will, according to our opinion, still retain its ascendency over every other description of material in the formation of vessels of war. Besides, there is every prospect that the improvements in the manufacture of steel will tend still further to increase the strength, lightness, and superiority of these important structures.

103

CHAPTER VII.

ON THE VARIED FORMS OF CONSTRUCTION OF SHIPS OF WAR AND THEIR ARMAMENT.

1. Ar the commencement of the Crimean war, ten years ago, His Imperial Majesty the Emperor of the French first suggested, that to cover the sides of ships with thick iron plates would render them impervious to shot, and the first ship that, pro- . perly speaking, had her sides protected in this way was the 'La Gloire.' She was cased with 44 inches thick armour plates, fastened with long bolts screwed into the timbers, and was considered at the time to be impregnable and perfectly shot-proof; which was the case, as the heaviest ordnance then in use was the 68-pounder smooth-bore gun.

The success of the La Gloire,' and the apparent security which she indicated in her new dress, led to distrust in every other vessel that was not protected by a covering of impenetrable armour plate. For a time it was doubtful to what extent this new system of armour covering was serviceable, and how it could best be applied to existing ships. This was a debatable point, and many were the projects elicited for that purpose, and the rooms of the Admiralty were inundated with contrivances, from which it was impossible to make a selection calculated to meet the requirements necessary to convert two and three-deckers into serviceable armour-plated ships. The result of all this conflicting testimony was that new ships must be built; and to render them as nearly as possible fire-proof and shot-proof, it was decided to build them entirely of iron. In the meantime it was necessary to be prepared, and not only were the 'Warrior' and 'Black Prince' placed upon the stocks, but several of the large two and three-deckers were cut down and lengthened and plated