In Great Britain the navy has always been considered the main defence. Its support and development have for over two hundred years been considered of the first importance, and, in legislating for its maintenance, expense has seldom been spared. Since the Crimean war, no sudden strain has been imposed upon its administration tending to limit development to certain especial types. Experiments have been carried on with equal profusion in all types, from the line-of-battle ship to the gun-boat, and as each experiment resulted in the addition of a vessel to the fleet whose lifetime could be estimated safely at fifteen years, we find in this immense navy a most heterogeneous collection of ships, which it would be impossible to classify distinctly. Although this heterogeneousness is a certain sign of extravagance, it by no means follows that it is a sign of weakness in the fleet itself. In all this range of liberal experiment there has been but one point where Great Britain has been really hampered, and the true advantage of a certain amount of restraint is well exemplified in the superiority of development brought about by it in this instance. In order to keep the fleet constantly up to the standard in number of vessels, a greater expenditure of timber was required than could be supplied by home production. It was easily foreseen that in case of a foreign war no dependence could be placed upon a constant supply from abroad, and to remedy this evil we find Great Britain the first to utilize iron in ship-construction, and battling against the first and apparently insurmountable obstacles to carry iron ship-building to perfection, making it immeasurably superior to wood, and through its use extending the range of architectural development far beyond the old limits.