A Treatise On The Principles And Practice Of Dock Engineering

368 DOCK ENGINEERING. 3. By direct transfer to lorries and vehicles. In this case the distance the goods are to be taken will not be great. 4. By temporary discharge upon the quay and subséquent transference by canal, rail, or road, as the case may be. These methods may be found both singly and in combination at the same port. With the first, however, we need not concern ourselves as it is outside the seope of the present section. The second and third methods may be considered conjointly as representative of direct transfer in contra- distinction to the fourth method which we will term indirect transfer. It is not difficult then to understand that based upon these methods there have arisen two separate and distinct systems of transit sheds, viz. : —(1) Those in which the shed fronts are brought very close to the face of the quay wall, leaving only a narrow margin of from 5 to 10 feet for foot traffic ; and (2) those in which the sheds are situated at a distance back from the edge of the quay, sufficiently great to admit of two or more lines of railway running parallel to the quay within the space intervening between the shed and the dock. The latter type of shed is in vogue at Marseiiles, Hamburg, Bremen, and most Continental ports, which may be called ports of transit. It is eminently suited to those cases in which a ship’s freight is trans- ferable without the necessity of selecting and sorting. The former system is practised at Liverpool, the older docks at London, and in other places where reverse conditions obtain and goods require subdivision before removal. Such ports may be distinguished as ports of destination. Sometimes the two classes of shed are exemplified at the same place, as at Manchester. Of the two lines of rails at the dock side, that nearest the water will generally be used for the loading-off cranes. The second will accommodate the trucks to be loaded, and a third line may advantageously be added as a siding. Quay cranes, however, of broader gauge than the regulation 4 feet 84-inch track, if placed on pedestal platforms, as is frequently the case, admit of a line of trucks passing beneath and between them, thereby producing a considerable saving in quay space. The drawback to the arrangement is a lessening of the stability of the crane. Occasionally, cranes may be found located, so that the outer end of the pedestal runs upon a rail at the quay level, while the inner end is carried on a rail fixed to some part of the shed structure, as in fig. 393. When the shed is close to the quay the discharging cranes must neces- sarily be situated entirely upon the shed, either at the roof or some intermediate floor level. The two arrangements of quay sheds are illustrated in figs. 349 and 350, which are ground plans respectively of sheds at Bremen and Liverpool. A considerable portion of a ship’s cargo may be raised from the hatches by the ship’s own appliances, and trucked ashore on gangways, or even, when the vessel’s sides are at some height above the quay, discharged by