SPECIAL TYPES OF POWER SHIPS As the steamship improved and as the shipping business be came more complicated and exacting, special types came into existence in considerable numbers.
Train Ferries.—The 417-ton steam train ferry "Leviathan," built in 1849 for the North British Railway Company to run across the Firth of Forth from Granton to Burntisland, was the first of a type which has now become quite general and which has been built to large size on several services. Almost at the same time another was built to cross the Tay at Dundee, but both these ferries were later replaced by bridges. In 1878 the Phila delphia and Reading Railroad built their first ferry steamer to run across New York Bay and in the early 'eighties the Danes started a train ferry from Korsor to Nyborg. The idea of a similar service to run across the Straits of Dover has constantly been suggested without success and an ambitious scheme for a train ferry between Sweden and England is now being discussed, but numerous difficulties have arisen in each case and the only train ferry on a large scale in Great Britain is that running from Har wich to Zeebrugge and employed very largely for the carriage of French and Italian fruit to England. The biggest ship of the train ferry type in which the trains run straight on to the rails on the deck of the ship is the "Contra Costa" in California, a wooden vessel with a gross tonnage of 4,483, built in 1914, but big vessels are now building and projected in which the rolling stock is lowered on to the rails by cranes.
Steam Trawlers.—In the early 'seventies several attempts were made to introduce steam trawlers in the South of England, but they were not successful. Some years later a shipping slump caused numerous steam tugs to be laid up and the experiment was tried of using some of these for trawling. Most of these were paddlers, the first being the "Messenger" which made her first trip to the fishing grounds in 1877, but the experience gained in her and other converted ships showed that the paddle was unsuitable for the purpose. Experiments with screw boats were tried in the
early 'eighties and were an immediate success, the design devel oping rapidly and producing some of the finest sea boats afloat.
At the present time practically every maritime country has its big fleet of power trawlers and drifters. The internal combustion engine has made great strides in vessels of this type recently and electric machinery has also been tried on occasions.
Icebreakers.—"Eisbrecher I.," launched in 1871, was the first specially designed icebreaker to be built. She was planned on the experience gained a few years previously by a Russian shipowner named Britneff, who reconstructed the bow of the steamer "Pilot" in such a way that she could be driven on to the ice in the hope that she would break it by her own weight. In practice she was too small and light for this purpose, but the idea was appreciated and is embodied in all modern icebreakers, some of which run to a large size.
Tankers.—The increased consumption of oil for various pur poses made it necessary to evolve some means of carrying it in bulk instead of in barrels as it had been carried from the earliest days of whaling. The first suggestion was in 1863, when the sail ing vessel "Ramsey" had a few tanks built into her hold to carry oil in bulk in addition to stowing barrels in the ordinary way in her 'tween decks. From 1869 to 1872 the sailing vessel "Charles," of 794 tons, was carrying oil in 59 iron tanks which were built into her holds and which completely filled them. The problem of keeping ironwork oil-tight was not then fully understood and these tanks were far too weak, with the result that in the working of the ship under sail constant leaks developed and eventually she was burned at sea. Several other ships were converted in similar fashion, mostly for the trade across the Atlantic to Havre and Antwerp, but they were all failures.