The suggestion of iron for building ships was met at first with ridicule; some people, of course, thought that an iron ship would surely sink, and more serious objections were found in the cost, the derangement of the compass, and the fouling of the ship’s bottom. Iron, however, came gradually into use for steamers, and, after 1850, was applied more and more generally to the constructions of sailing vessels. Iron vessels were actually superior in buoyancy to wooden, drawing less water and carrying more cargo with a given tonnage; they were cheaper in the long run, because they are stronger, more durable, and less exposed to destruction by fire. Furthermore, iron was absolutely essential if the size of ships was to be increased. Builders of wooden ships were limited by the average height of trees, and, in spite of all devices, could not construct a frame sufficiently strong for a vessel exceeding about 300 feet in length. The size of an iron or steel ship is practically unlimited. The cost of ships constructed of metal has decreased with advances in the manufacture of iron and steel; remedies, fairly satisfactory, have been found for the derangement of the compass; and though it has been found impracticable to apply copper sheathing to steel ships, the fouling of the bottom is an evil of minor importance. =356. Relative decline of sailing vessels, notwithstanding improvements.=—During the second half of the nineteenth century the wooden ship gradually disappeared from the seas, giving place to vessels constructed first of iron and then of steel. The country which suffered most from the change, as will appear later, was the United States; the country best prepared to profit by it was England. The English now rapidly enlarged the dimensions of their ships, and improved their rig and model. Some of the modern steel ships carry 5,000 tons of cargo, or even more. A study of winds prevailing on the ocean, to which an American officer, Maury, made important contributions, enabled sailing vessels to choose a course which, on many routes, shortened the duration of the voyage a third or more. Steam has been applied for handling the cargo, and for managing the rudder and sails. In spite of all improvements the sailing vessel has not been able to keep its share of sea-borne commerce. So much depends on certainty in modern business that the merchant will gladly pay a higher freight rate to be relieved of the element of uncertainty which is bound to attend navigation by sails. Steamers now exceed the sailing vessels of the world not only in tonnage, and still more in effective carrying capacity, but even in number also, if only vessels of 100 tons and above are counted.