The large cargoes now carried and the very mixed nature of the commodities necessitate in most cases landing on the quay for sorting before delivery. This requires much floor area, and has led to the introduction of two or more floor transit sheds to avoid excessive congestion of the cargo when landed. And for the subsequent delivery of these goods by rail or road, special facilities are needed. A single cargo of 8,000 tons of general cargo, if all had to be despatched by rail, would require ',coo trucks to take it away. These trucks would occupy 3,00o yards of railway, which is some measure of the amount of siding ac commodation which has to be provided for the efficient working of a discharging berth and also the great relief obtainable when a large part of the work is done by barge. The movement of these trucks has to be performed without interference with the work at adjacent wharves; hence the proportions which the three methods, barging, railway and road transport, bear to each other must largely affect the design of the shore equipment of a port.
The quick and economical movement of cargo is now largely obtained by the provision of mechanical appliances in substitu tion for manual labour, and the main staples when arriving or being despatched in whole cargoes, or in large quantities in mixed cargoes, are usually dealt with by special machinery, e.g., for export, coal, and for import, grain, timber, meat and provisions, for all of which specially designed conveying machinery is in stalled at every port where the tonnage is sufficient to justify the expenditure. Mixed cargoes are discharged either by cranes on the shore or by the ship's gear. Such equipment is usually pro vided by the port authority.
The Provision of Port Machinery.—But as ships are often required to receive and deliver cargo in the open roadstead or at ports abroad not equipped with shore appliances, they must nec essarily be fitted with booms and winches, and it is, therefore, often economical to make use of these appliances even when shore plant is available. In practice, however, competitive reasons compel port authorities to provide cranes, and in many cases more specialized working plant. Coal is shipped by means of (a) tips or hoists in which the wagon is lifted to a height above the ship's deck and the contents tipped into a shute to fall into the hold, (b) staithes, when the configuration of the ground permits, where the wagon is pushed to above deck level and the contents tipped into the hold, and (c) conveyors in which case the wagon at quay level is discharged on to a conveying band to the hatch. The last method is coming into increasing use. Grain is now mostly imported in bulk and is discharged by means of elevators which lift it in a continuous stream from the hold, convey it to the quay, and there deposit it on to conveying bands which carry it to silos where it is either stored or delivered by gravity into sacks for inland transport. These elevators are of either the bucket or the pneumatic type. When grain is imported in sacks the modern practice is to cut the bags in the ship and "start" the contents into bulk for discharge by this more eco nomical method. Grain elevators may be either fixed on the
quay or mounted on floating pontoons. The latter, though more costly, has the advantage of greater mobility. Grain discharging machinery has been passing through many stages of evolution during the last twenty years, and the pneumatic type seems to be gradually getting established. For inland transport in England and on the Continent (in contrast to all countries in America) the uneconomic method of carriage in sacks is still prevalent, but a small beginning has been made with bulk transport by rail.
Ores are now generally discharged by grab cranes which are self-filling and save the labour of loading into tubs. Iron is largely discharged by means of an electrified block on a crane which attracts the iron and when over the selected site releases by cutting off the current. Petroleum is usually discharged through pipe lines from the shore storage to the quays. This pipe is con nected by means of a flexible hose to the ship's tank and pumped to the storage tanks. The same method is employed for vegetable oils and for molasses where the volume of trade is sufficient to justify the cost of the installation.
With free trade and the removal of customs restrictions, the tendency is increasing for the importing merchant to sell his goods "ex ship," and for goods to pass at once on discharge into consumption, but raw materials are still largely stored in dock warehouses or in adjacent warehouses of private owners for later consumption. Such deliveries are largely of a retail nature, and many of the chief ports have provided elaborate facilities for the storage, sampling, handling and accounting of warehoused goods. This branch of activity prevails in British and in some American ports more than on the Continent of Europe.
Rail Terminals and Docks.—At ports where barging is not the predominant method of handling cargo and at all modern ports to a greater or less degree, the railway facilities are an important feature as affecting the cost of distribution. There is great variety of method. At some railway-owned ports the docks are treated as a terminal goods station under main line control. At others, the railway working is self-contained under the docks superintendent. This affects the design of the railway system and the methods of working. In non-railway docks in some cases the railway company is given running powers to the quays, in others the port authority conducts its own railway oper ation. As in every properly conducted dock the first and principal aim is to give the ship despatch and with that object to avoid, by its rapid removal, the congestion of cargo at the ship's side, modern practice is to confide the control to the authority respons ible for the despatch of the ship, providing an area away from the ship where the traffic is interchanged with the main line railway. In the United Kingdom this area is called the "exchange sidings"; in America the "belt line." One or more such points of inter change may be provided in accordance with the physical condi tions of the main railways serving the port.