The crown is thus for the moment with the White Star, nor is it likely to be torn away by anything short of the tremendous effort involved in putting afloat a new, a bigger, and a more costly ship. Owners must, of course, count the cost of such rivalry and must put against the gain of say sixteen hours, in order to come to the desired five days and twenty-three knots, the cost of the thousand or twelve hundred tons more of coal which will have to be burned, the doubled number of engine and fire-room force, the larger crew, the interest on the greater investment. It is a large price to pay for a gain of so small a bit of that we generally hold so cheap—but it will be paid. * * * * * It has been impossible, of course, in a single chapter to do more than touch upon the vast changes, and their causes, which have had place in this great factor of human progress. Higher pressures and greater expansions: condensation of the exhaust steam, and its return to the boiler without the new admixture of sea-water, and the consequent necessity of frequent blowing off, which comparatively but a few years ago was so common; a better form of screw; the extensive use of steel in machinery, by which parts have been lightened, and by the use of which higher boiler-pressures are made possible—these are the main steps. But in addition to steel, high pressures, and the several other elements named which have gone to make up this progress, there was another cause in the work chiefly done by the late W. Froude, to be specially noticed as being that which has done more than the work of any other man to determine the most suitable forms for ships, and to establish the principles governing resistance. The ship-designer has, by this work, been put upon comparatively firm ground, instead of having a mental footing as unstable, almost, as the element in which his ships are destined to float. It is not possible to go below the surface of such a subject in a popular paper, and it must suffice to speak of Mr. Froude’s deductions, in which he divided the resistances met by ships into two principal parts: the surface or skin friction, and the wave-making resistance (which latter has no existence in the case of a totally submerged body—only begins to exist when the body is near the surface, and has its full effect when the body is only partially submerged). He showed that the surface friction constitutes almost the whole resistance at moderate speeds, and a very great percentage at all speeds; that the immersed midship section area which formerly weighed so much in the minds of naval architects was of much less importance than was supposed, and that ships must have a length corresponding in a degree to the length of wave produced by the speed at which they are to be driven. [Illustration: The Chilian Cruiser Esmeralda.]