Having often observed, when at sea in heavy weather, how the pitching of the vessel caused the weights on the safety-valves to act irregularly, thus letting puffs of steam escape at every heave, and as high pressure steam was too valuable a commodity to be so wasted, we determined to try direct-acting spiral springs, similar to those used in locomotives, in connection with the compound engine. But as no such experiment was possible in any vessels requiring the Board of Trade certificate, the alternative of using the Camel as an experimental vessel was adopted. The spiral springs were accordingly fitted upon the boiler of that vessel, and with such a satisfactory result that the Board of Trade allowed the use of the same contrivance on all the boilers of the Oceanic and every subsequent steamer, and the contrivance has now come into general use.
It would be too tedious to mention in detail the other ships built for the White Star line. The Adriatic and Celtic were made 17 feet 6 inches longer than the Oceanic, and a little sharper, being 437 feet 6 inches keel, 41 feet beam, and 32 feet hold.
The success of the Company had been so great under the able management of Ismay, Imrie and Co., and they had secured so large a share of the passengers and cargo, as well as of the mails passing between Liverpool and New York, that it was found necessary to build two still larger and faster vessels--the Britannic and Germamic: these were 455 feet in length; 45 feet in beam; and of 5000 indicated horse-power. The Britannic was in the first instance constructed with the propeller fitted to work below the line of keel when in deep water, by which means the "racing" of the engines was avoided. When approaching shallow water, the propeller was raised by steam-power to the ordinary position without any necessity for stopping the engines during the operation. Although there was an increase of speed by this means through the uniform revolutions of the machinery in the heaviest sea, yet there was an objectionable amount of vibration at certain parts of the vessel, so that we found it necessary to return to the ordinary fixed propeller, working in the line of direction of the vessel. Comfort at sea is of even more importance than speed; and although we had succeeded in four small steamers working on the new principle, it was found better to continue in the larger ships to resort to the established modes of propulsion. It may happen that at some future period the new method may yet be adopted with complete success.
Meanwhile competition went on with other companies. Monopoly cannot exist between England and America. Our plans were followed; and sharper boats and heavier power became the rule of the day. But increase of horse-power of engines means increase of heating surface and largely increased boilers, when we reach the vanishing point of profit, after which there is nothing left but speed and expense. It may be possible to fill a ship with boilers, and to save a few hours in the passage from Liverpool to New York by a tremendous expenditure of coal; but whether that will answer the purpose of any body of shareholders must be left for the future to determine.
"Brute force" may be still further employed. It is quite possible that recent "large strides" towards a more speedy transit across the Atlantic may have been made "in the dark."The last ships we have constructed for Ismay, Imrie and Co. have been of comparatively moderate dimensions and power--the Arabic and Coptic, 430 feet long; and the Ionic and Boric, 440 feet long, all of 2700 indicated horse-power. These are large cargo steamers, with a moderate amount of saloon accommodation, and a large space for emigrants. Some of these are now engaged in crossing the Pacific, whilst others are engaged in the line from London to New Zealand; the latter being specially fitted up for carrying frozen meat.
To return to the operations of the Belfast shipbuilding yard. Aserious accident occurred in the autumn of 1867 to the mail paddle-steamer the Wolf, belonging to the Messrs. Burns, of Glasgow. When passing out of the Lough, about eight miles from Belfast, she was run into by another steamer. She was cut down and sank, and there she lay in about seven fathoms of water; the top of her funnel and masts being only visible at low tide. She was in a dangerous position for all vessels navigating the entrance to the port, and it was necessary that she should be removed, either by dynamite, gunpowder, or some other process.
Divers were sent down to examine the ship, and the injury done to her being found to be slight, the owners conferred with us as to the possibility of lifting her and bringing her into port.
Though such a process had never before been accomplished, yet knowing her structure well, and finding that we might rely upon smooth water for about a week or two in summer, we determined to do what we could to lift the sunken vessel to the surface.
We calculated the probable weight of the vessel, and had a number of air-tanks expressly built for her floatation. These were secured to the ship with chains and hooks, the latter being inserted through the side lights in her sheer strake. Early in the following summer everything was ready. The air-tanks were prepared and rafted together. Powerful screws were attached to each chain, with hand-pumps for emptying the tanks, together with a steam tender fitted with cooking appliances, berths and stores, for all hands engaged in the enterprise. We succeeded in attaching the hooks and chains by means of divers; the chains being ready coiled on deck. But the weather, which before seemed to be settled, now gave way. No sooner had we got the pair of big tanks secured to the after body, than a fierce north-north-easterly gale set in, and we had to run for it, leaving the tanks partly filled, in order to lessen the strain on everything.
