In 1858 the United States Navy put forth a type of vessel new in every particular, and one whose value, although not immediately recognized, has by its development become the true standard for effective medium unarmored cruisers. The Hartford, Brooklyn, Richmond, and Pensacola combined all the advantages of both the second-class frigate and the sloop-of-war. With a displacement of 3000 tons, which placed them in a line with light frigates, their steam-power was fully developed, whilst steaming capacity and sail-power were kept at a maximum, and strength of battery combined, in the best manner, calibre and number of guns. In the civil war, which soon followed, no class of vessels proved itself of so much fighting value as this. These vessels formed a distinct class in the navy, and contemporaneously with them appeared a third and lighter class (Iroquois, Wyoming, Mohican, and Narragansett), with a displacement ranging from 1600 to 1900 tons. In France this latter type had appeared in the navy at the same time, the Cosmao and Dupleix, with a displacement of 1800 tons, realizing a speed of nearly two knots greater (12 knots), whilst steaming capacity and sail-power were the same, and the battery was inferior in about the same proportion as the speed was superior. In England the development of this class was an extension of the old steam-sloop, realizing in the Challenger and Barossa type a displacement of 2350 tons, with the disadvantages of excessive draught of water, lack of development of speed and steaming capacity. No better evidence of the complete demoralization of architectural development in the United States can be found than in the movement made in 1872, in which the Hartford class, after having established thoroughly its great utility, was by the addition of a spar-deck reduced to the plane of the Challenger, with increased draught, reduced speed and steaming capacity, and in fact a reduction of all the qualities which had rendered it superior, notwithstanding the total disappearance of the type not only in the English but in all foreign navies. During the Crimean war a great number of gun-boats, ranging between 500 and 800 tons displacement, had been hastily but well constructed, and the type was continued after the war until 1860 almost without change. The same types with but slight modifications were contemporaneously introduced in France, those of the French Navy, as a rule, possessing a superiority in speed of about one knot. With the Immortalité frigate, the Challenger sloop, and the Britomart gun-boat, the development of wooden war-vessels ceased in England in 1859, giving place to composite and iron construction.