The total ruin of American commerce, brought about by the depredations of half a dozen Confederate cruisers, led to the introduction of four new types of ships, and in these types American constructors sought in general to realize the maximum of speed without reducing any of the other qualities. The first of these (in point of rate) was designed entirely with a view to securing the highest possible speed and steaming capacity, all other qualities being made subordinate. The displacement of this type was between 4800 and 5000 tons, ranging about 300 tons higher than the frigates of 1855, and they were designed for a speed of 17 knots, with a steaming capacity of 5600 miles at 10 knots. The speed alone was realized. The ships themselves being built of white oak rotted almost before they could be launched; the frame was not of sufficient strength to resist the powerful working of the engines or the wear and tear of cruising, failing in this particular as the English frigates Mersey and Orlando had in 1858. The consumption of fuel was beyond the calculations, reducing the steaming power to less than 3500 miles. The second type was that of a fast frigate, or more properly first-rate (Piscataqua), in which strength of battery and sail-power were raised to their old proportions with regard to the displacement. The displacement of this type was 4000 tons, battery 25 nine-inch smooth-bores, and speed 12 knots, with a steaming capacity of 3000 miles at 10 knots. These ships were also built of white oak and soon rotted, and their general unhandiness combined, with the great expense of keeping them in commission, caused the type to drop out of existence. The third type (Congress), having a displacement of 3000 tons, came nearer to the requirements of a large fast ocean cruiser than either of the others, proving fast under steam or sail, handy, and carrying a well-proportioned battery. This type died out with the others in the general demoralization following the reduction of the fleet after the war. The fourth type (Plymouth), having a displacement of 2400 tons, with a battery of 12 guns and a speed of 12 knots, was in reality a development of the Shenandoah class, having for an increase of 300 tons a gain in battery proportional, and a maximum of speed both under steam and sail without any increase of draught. Of the four types, this one alone, which was a development of the Shenandoah class, the latter being modified from the Hartford, was the only real step in advance; but even this type has passed from the active list at present.