The life of the iron or steel floating dock of whatever type is likely to be far longer, if care be taken of the structure, than might at first be supposed. Rennie’s Cartagena dock, built of iron in 1859, was in such splendid condition when the proposal was made to build a Havana dock that as a counter-proposal it was suggested to send the Cartagena dock there. The _Nicolaieff_ built in 1876, has been uninterruptedly employed ever since in lifting the vessels of the Russian Navy. The Victoria Dock is 310 feet in length, and of the hydraulic-lift type, with a lifting power of 3000 tons, and has nine pontoons or trays of a total length of 2185 feet, and an aggregate lifting power of 17,060 tons; the pontoons were constructed between 1857 and 1876, the largest of them being of 5000 tons. The Malta dock, also of the hydraulic type, is 340 feet in length, with a lifting power of 4000 tons, and was built in 1871. It has two pontoons of 4000 and 2500 tons respectively. The hydraulic floating dock at Bombay, built in 1872, was rather larger, being 400 feet in length with a lifting power of 8000 tons, its pontoon of the same length lifting 6500 tons. These lifts were designed by the late Edwin Clark, M.I.C.E., who introduced floating docks from which the present types have directly sprung. These hydraulic docks are no longer at work. The carrying of railway trains by ferry-steamers across stretches of water too large to be bridged over is no new thing, there being several such in the United States and Canada. Many of the vessels thus employed are of considerable size. These waters are comparatively landlocked, and the traffic, except in unusually stormy weather, is seldom interrupted. The American ferry-boats are double-ended, so that a train can enter at one end and leave at the other after crossing the water, the ends of the ferry-boat and of the pier supporting the shore lines being constructed to fit exactly. Most of the modern American ferry-boats taking railway trains have two, three, or four sets of rails on their decks, and accommodate their passengers on a deck above, where the saloons and cabins are situated. Where the railway-level is different on the two sides of the water, the boat or the landing-stage is provided with hoisting machinery which raises the train to the desired level, a truck or two or a passenger coach at a time.