means of slides. Where there are no cranes these methods must obviously be adopted; but the question of unloading appliances is more suitable for discussion under the section of Working Equipment.

On the landward side of the shed, will generally be found a roadway for cart traffic, often in conjunction with additional lines of railway.

The level of the shed floor is another point concerning which opinion is divided. At some ports it coincides with the quay level; at others it is raised 3 feet or more above the quay, the object in the latter case being to bring it on a plane with the floors of waggons and carts so as to facilitate trucking. This method forbids, while the alternative method allows, carts and vehicles to enter the shed, and so to a certain extent to obviate trucking. Local practice, again, influences the decision as to which method in preferable.

As illustrating the diversity of opinion prevailing in regard to the general disposition of sheds and warehouses, and the utter impossibility of formulating any definite or systematic regulations thereon, the following conclusion, unanimously adopted after a long discussion of the subject by the members of the Seventh International Maritime Congress (Fourth Section-Seaports) sitting at Brussels in 1898, may be quoted:

"Question.-Warehouses and sheds: accommodation, size, mode of construction, means of access.

"Conclusion.-Considering the preponderating influence which variable elements in the different ports, especially the nature of the traffic and the commercial customs, must have on the conditions of the establishment of quays and warehouses, the Fourth Section is of opinion that there is no occasion to draw up general rules with regard to these conditions of establishment, as the arrangements adopted in each particular case are of interest solely by way of indication for analogous cases."

Features of Construction. - Methods of shed construction fall largely under those of building generally, and it is not proposed here to discuss details which are common to ordinary structures, and for which reference may be made to any suitable text-book on building construction. Those

features alone will be dealt with which are essential and prominent from the point of view of a dock engineer.

It is manifestly desirable that sheds (and warehouses) should be, as far as possible, of thoroughly fireproof construction throughout. From motives of economy, however, the former are often constructed of inflammable material, such as timber and zinc. Single-storey sheds are most noticeable in this respect.

Doorways.-The openings in the sides of a shed, both at the dock front and along the roadway, should be as numerous as possible, more particularly in the first case, so as to be adapted for receiving the discharge from several hatchways simultaneously. It is a good plan to have continuous doors, on account of the difficulty of getting several ship's hatchways to coincide with

isolated door openings. With this arrangement, the sides of the shed will consist of a series of columns with intervening spaces, generally closed by doors, but sometimes, as at Havre, without them. At the same time, it must be remarked that the absence of longitudinal walls causes a shed to lose much of its stiffness as a structure, and deprives it of the means of affording lateral support to its contents. Grain discharged in bulk is often prevented from spreading, on one side at least, by an external wall or partition, with a consequent saving in space, and similar assistance is rendered in the case of many other classes of goods. This fact emphasises the necessity for substantial sides to a shed. The advantages of continuous doorways, moreover, on the roadside are more imaginary than real. Not more than one-half

the entire length can be available open space, and the only benefit conferred is that of exercising some restricted choice as to its disposition.

Doors are of two varieties-rolling (or sliding) and folding.

Rolling or sliding doors consist of frames of timber or iron, with a facing of the same material. Movement is made with wheels, which run either on a ground rail or upon a rail above the door. The grooves in a ground rail are liable to become choked with dirt and grain, and need frequent cleaning.

The

Figs. 353 and 354.-Iron Shed Door-Elevation and Vertical Section. They hold water, which in winter freezes and causes inconvenience. use of lower wheels further necessitates an upper guide rail for the top of the door. Usually two rows of slide rails are provided, the doors being arranged in pairs to overlap slightly. Fastenings are made in the usual way by drop-bolts, hasps, &c. Fig. 351 is an elevation of a wooden, and fig. 353 of an iron, door constructed in this manner at Liverpool.

Folding doors are flexible sheetings of wood or metal, so contrived as to be wound round a roller at the top of the doorway. Details of one in use at Dundee are given in figs. 355 to 360. It is constructed of pitchpine laths threaded on steel wire, and fastened to an iron drum, 12 inches in diameter. By means of balance weights and simple gearing, one man can, with ease, lift and lower the sashes.* Folding doors are lighter and take up less space than sliding doors. At the same time, sliding doors are stouter and offer a greater obstacle to the passage of fire.

The effect of fire on iron (or steel) doors is somewhat curious. Under the influence of intense heat they curl up and twist like a piece of burning paper. This erratic behaviour constitutes a source of peril, and some have even gone so far as to advocate the adoption of wooden doors on the ground that they burn away in comparative harmlessness.

Compartments.-When a shed is of considerable length, it is advisable to divide it into a series of compartments, within any one of which an outbreak of fire can be completely confined. Division walls between adjoining compartments should then be carried some 5 or 6 feet above the roof line, in order to cut off all connection. For the same reason, any door openings in such walls should be fitted with double doors. The system of detached compartments, with intervening alley ways, is a greater safeguard, but it involves less economy in space and greater expenditure in construction.

*G. C. Buchanan on "The Port of Dundee," Min. Proc. Inst. C.E., vol. cxlix.