As an example of the saving that can be effected by mere mechanical contrivance, we take a new ship of the Inman line trading between Liverpool and New York, in which the old style of engine has given place to the 'modern double cylinder compound engines,' which leave a much larger space for cargo than the old engines, and burn about sixty-five tons of coal per day, instead of one hundred and fifteen tons. The saving in the article of fuel is thus seen to be very great, even for a single ship.
Of course iron and steel were prominent topics of discussion at the meeting, and the conclusion to be drawn therefrom is, that in ship-building and other mechanical operations steel will take the place of iron. The torpedo vessel Lightning, which steams nineteen knots an hour, is already an evidence of what can be done by the combined lightness and strength of steel; another is promised by Admiral Sartorius, which will cleave the water at the rate of twenty-four knots, and steel ships of large size are building and to be built for the government. In this way the peaceful arts become diverted to warlike purposes, and heighten the cost of war to a prodigious extent.
The future of steel, said Mr Bramwell, F.R.S., in his lecture at the Royal Institution, is to supersede iron for almost everything except the forge-work of common blacksmiths; and further, that part of the province of cast-iron, such as toothed-wheels and castings of complex form, which now, thanks to Riepe's improved construction of moulds, can be produced from molten steel.
Mr Siemens' process for the manufacture of steel leaves nothing to chance. The quality of steel is always that which was foreseen and desired; and the samples, when submitted to the severe tests imposed by the Admiralty, are never found to fail.
But Professor Barff's discovery seems to shew that iron will not be easily superseded. If iron can be produced that will not under any circumstances get rusty, iron will become more useful than ever. The discovery is this: that if hot iron is placed in a chamber of superheated steam, it takes on a black coat which is magnetic oxide, and this coat is so hard and impervious to atmospheric influences that rust will not form upon it. The hotter the steam in which the process is carried on, the harder is the coat: after an exposure of seven hours to twelve hundred degrees, it will resist a file. Consequently the strength of the iron is greatly increased, and it can never become weakened by rust. The importance of this fact can hardly be overrated in connection, for instance, with iron plates for boilers and ships, in which unlimited strength would be highly prized.
We are told that the protecting coat can be put on at small cost, and that it will probably be made use of for iron goods of every description. 'Copper vessels will no longer possess any advantages for cooking, and iron saucepans will no longer need to be tinned. Lead pipes for the conveyance of water will in all probability be entirely superseded; and there can be no doubt that new uses for incorrodible iron will every day suggest themselves. Messrs Penn of Greenwich are about to undertake a series of trials for the purpose of testing the strength of the prepared articles, so that they may become able to speak with authority upon the fitness of the protected iron for bridge girders and architectural purposes.'
How to make iron without producing slag is a question which, if any one can answer satisfactorily, his reward shall be great in fame and fortune. In Yorkshire alone, the blast-furnaces pour out more than four million tons of slag a year, from which fact the enormous quantity produced throughout the kingdom can be judged of. Sixteen million tons of refuse! What can be done with it? In some places, land has been bought or hired to provide space for the ugly heaps, and many attempts have been made to lessen the accumulation by finding uses for the slag. It has been made into blocks and bricks for paving; into slabs, pipes, brackets, and friezes; into cement; into sand for fertilising purposes; and while in the molten condition, has been blown into a substance resembling cotton-wool. But some of these attempts have failed, and not one has sufficed to diminish the heaps of slag. And now another suggestion, based on the fact that slag is vitreous, is put forth, namely to convert it into glass. A mixture of sand, soda, and slag melted in a furnace will come out as glass. The experiment would not be expensive, for slag in any quantity may be had for nothing.
If some of those ingenious individuals who write so frequently to the Admiralty or to the Royal Society announcing that they have discovered the true place of the axis of the earth, or the true explanation of the precession of the equinoxes, or the cause of compass deviation, would only turn their attention to the questions in the foregoing paragraph, they might perhaps make practical discoveries which would be capable of proof, and potential of profit.
Last session a paper on the Best Method of Propelling Steamships was read at the United Service Institution. In the discussion that followed, Admiral Selwyn said experiment had shewn that whether you divide the water by a very narrow fine bow, cleaving the fluid like an axe, or whether you put that narrow fine bow flat on the water, and drive it over the water, the resistance is for all practical purposes the same: having fine lines there is no more resistance in the one case than in the other. Experiment has shewn also that between the finest vessel of deep draught and a vessel of similar tonnage, built in the form of a segment of a sphere, there is no difference of resistance. 'But there is this remarkable difference in another way, that whereas the sharp deep-keeled vessel plunges constantly under water, and makes bad weather of it, the segment of the sphere always rides over the water with perfect ease.'
And at the meeting of Naval Architects, Mr Reed explained that a circular ironclad will float better and carry heavier weights than a ship of the ordinary shape, and yet not be deficient in speed.