As the reverse of being specially adapted for a particular service, the steam tramp is built so that she can readily engage in almost any carrying trade. Unlike the liner with her fixed routes and set times of departure and arrival, the tramp is a nomad, and wanders over the world picking up a cargo here and there, and taking it across the ocean at her economical but jog-trot speed. If there is nothing for her to pick up at the last port of call she betakes herself elsewhere with the hope of better luck. Her main income is derived as a coal-carrier, and for this she is quite suited. But the modern collier--the kind of ship which is expressly built for the coal trade--is fitted with numbers of steam winches in keeping with the modern feverish haste and hurry, so that no sooner has she come alongside than she may instantly begin to unload. In old-fashioned times the discharging was done from the shore, but nowadays the up-to-date turret-ship makes short work of handling her black diamonds. Special appliances are also provided for those steamships which bring over the seas vast quantities of New Zealand mutton, fruit, and other perishable articles of food. Elaborate refrigerating machinery has to be installed in the ship, and special means employed to facilitate the disembarking of the cargo, especially in the case of the former. [Illustration: CANTILEVER-FRAMED SHIP. _By permission of Sir Raylton Dixon & Co., Ltd._] To a still more exceptional purpose has the steamship been adapted in order to act as an ice-breaker and give liberty to those ships which, in certain parts of the world, have, with the approach of winter, been compelled to enter a lengthy imprisonment. Such localities are found in both Canada and Russia. Thanks to the ice-breaker steamship it has been made possible to keep open the Baltic ports with a passage of sufficient width. Constructed of a strength which is possessed by no other vessel than a man-of-war, the ice-breaker attacks the frozen masses as a battleship used to ram her foe. She goes for the ship’s enemy with her curved bow, and wages war with all the ability which the ship-builder and naval architect have given her. Her bow is specially strengthened to suffer the force of the contact with the heavy ice masses, and the lines of the hull are such that the ice in its endeavour to crush the ship finds difficulty in getting a good grip upon it. Nevertheless, these ships are fitted with numerous water-tight compartments. Their means of propulsion are, of course, screws.