As the manufacture of mild steel progresses and extends, the assimilation of the rival materials as to cost is sure to follow. Already very great advances have been made towards this end, the fact being abundantly evidenced by the greatly increased number of steel ships on hand, and by the establishment of new works, and transformation of old, for the better production of the new material. In 1877 mild steel was about twice as costly as the iron in common use. The sources of supply, however, were then comparatively few, and the thorough and severe testing to which the new material had to be subjected, necessarily increased the cost relatively to iron, which has never been subjected to the same rigorous ordeal. In 1880, owing to the increased sources of supply and the progress in manufacture, the cost of steel had been reduced, relatively to iron, by about 50 per cent. At the time of writing (March, 1884), the price of steel for a good-sized vessel is—overhead—about seven pounds, seven shillings and sixpence per ton; while the corresponding figure for iron is about five pounds, five shillings, or a difference of only about twenty-nine per cent. in favour of the older material.
Doubts were at first expressed by not a few, regarding the durability of steel ships compared with those of iron, such misgivings being aggravated by the thinness of the steel plating. This fear is being gradually lessened by the results of laboratory experiments and bona fide experience—the broad deduction from which is, that the deterioration of steel, under the action of sea water, is no greater than that of iron, and that, if the same care and constancy in cleaning and painting, common to ships of the latter material, be extended to ships of the former, their durability will be equal.
Several large shipowning companies were not slow to place faith in the new material. In the early part of 1879, the “Allan Line” Company entrusted to Messrs Denny & Brothers, of Dumbarton, the order for a huge vessel, which the intrepid confidence of the principal partners in both the owning and the building firms determined should be of mild steel, be bound with steel rivets, and have her boilers of the same material. This was the large steamer Buenos Ayrean, the first transatlantic steamer built with the new material. She was finished early in 1880, and had not been over nine months in the water when the order for a second and still larger steel vessel—the Parisian—had been given by the same owners to Clyde builders. The Union Steamship Company of New Zealand, the Pacific Steam Navigation Company, Messrs Donald Currie & Co., and several smaller companies, ordered vessels of steel almost simultaneously, while yet the new material was in the early stage of trial. Amongst the orders for steel vessels which were subsequently given, the Servia and Catalonia, for the Cunard Company; the Clyde and Thames and Shannon for the Peninsular and Oriental Company; the India, for the British India Company; the Arabic and Coptic, for the Oceanic Steam Navigation Company, and the four twin screw steamers of the “Hill” Line, represent the principals. The companies who then adopted the new material have mostly continued to have their new ships built of steel, and to name the vessels since built and now building in which this material is employed, would simply be to enumerate three-fourths the fleet of high-class modern merchant ships. There were 21,000 tons of steel shipping built throughout the United Kingdom in 1879; 36,000 in 1880; 55,000 in 1881; 126,000 in 1882; and over 244,000 in 1883. It is computed that at the present time the amount of steel shipbuilding going on throughout the kingdom is not less than 175,000 tons, or the largest amount on hand at any one time since its introduction.
The modification in the structural arrangement of ocean trading vessels, already spoken of as the continuous-cellular system, although only within very recent times receiving extended adoption in the mercantile marine, possesses in some of its essential features the prestige of years. So long ago as 1854, Mr Scott Russell strongly advocated the principle of longitudinal construction, and applied it in practice to ships of the mercantile marine, to the success of which, in a scientific sense, the Great Eastern is surely overwhelming testimony. The principle met with much scientific favour from many besides Mr Russell, but it did not take root in solid practice. Pecuniary and other kinds of considerations interposed to prevent its general adoption. The urgency for increase in the size of vessels was not such as to make longitudinal strength (the special advantage claimed for the new principle) a great desideratum; and there was perhaps reluctance on the part of shipbuilders to relinquish time-tried and familiar methods. The system presently under notice—although, as has already been said, the same, in its main principles, as the system then advocated—by its descent through the Admiralty Dockyards, by its application to merchant vessels—first of East Coast, and then of Clyde build—and by its close association with water ballast, has undergone many modifications which almost constitute it a creation of recent times.
Sir Edward J. Reed, when Chief Constructor of the Navy, introduced the bracket frame system of construction into iron-clad ships of war, and, as already indicated, it is largely owing to the experience of the system as applied and practised in such cases—conjointly, of course, with its successful introduction in the case of the Great Eastern—that in so short a time it has reached the present structural perfection, and received such wide extension in merchant steamships. That it has recently received such wide adoption in the mercantile marine is due not so much to its structural advantages—and these are great—as to the way in which it lends itself to the economical working of steamships in actual service. This will be more explicitly referred to after some description of the system as applied in merchant ships has been given.
It is somewhat away from the field this work is concerned with, to trace the system in its stages of development in ships of war, but it may be said, shortly, that the impulse which the system has received in the mercantile marine has in no sense been a transference of the activity which at all times since its introduction has characterised the application of the system to the vessels built in our naval yards.
In order to assist the non-technical reader in appreciating what follows regarding the system in merchant ships, a general idea of the cellular bottom principle of construction is afforded by Fig. 1.
FIG. 1.
