be cited from Avonmouth, Cardiff (Roath Dock), and London (West India Dock, fig. 16).

The lozenge, or diamond, is a slight deformation of the square, resulting in an improvement of form when the entrance is at one of the acute angles, as is the case in the most noteworthy instance of its use-viz., at the Empress Dock, Southampton (fig. 1).

The machicolated form consists of any rectilinear outline in conjunction with a number of internal projections, often of the nature of jetties or staiths. It constitutes an admirable means of utilising large docks to their fullest extent, as will be evident from an inspection of the plans of the Alexandra Dock at Hull (fig. 12), the Victoria Dock at London (fig. 17), Penarth Dock, and others.

A particular variation, or possibly an evolution, of the previous type is the tridentine, in which a main dock is provided with three important arms or branches, perpendicular to it. Such is the shape adopted for the Tilbury Docks at London (fig. 9), the Alexandra and Huskisson Docks at Liverpool (fig. 5), and the Prince's Dock at Glasgow (fig. 10). There is no essential limit to the number of branches, but three appears to be a very serviceable number consistent with compactness of design. For reasons of traffic, the branches should be arranged to the landward of the main dock.

Finally, we come to yet another evolution of the machicolated, which, from its resemblance to the outspread fingers of a hand, may appropriately

ITCHEN.

be termed the digital. It is illustrated in fig. 2. The suggestion emanated, in the first instance, from the late Thomas Stevenson, but the design in the figure embodies several important modifications of the original sketch, and includes an entrance scheme which has not, to the author's knowledge, appeared elsewhere. The idea is that the dock is situated on the margin of a tidal river, or estuary, and the dual entrance, as explained in Chapter vi., is intended to permit of the dock being accessible at all stages of the tide. When the flow is up the river, vessels will enter by the upstream locks and depart by the downstream locks. Vice versa, when the tide is running out, incoming vessels will use the downstream locks, and those departing, the upstream locks. In this way the dock will be worked without intermission and without obstruction. It is assumed that the outer sills are deep enough to allow vessels to pass over them at low water.

The scheme has been amplified so as to include all the features essential to a dock system. Graving docks of various sizes are arranged between the entrance locks, with ample intermediate space for ship-repairing depôts. In order to have shoreward connection for these, it will be necessary for the locks to be spanned by movable bridges.

The central portion of the dock is semi-circular in form, and designed to afford turning room for vessels up to 1,000 feet in length. There are also four utilisable berths, each 275 feet long.

The branches, of which there are five, though irregular in form are all similar, and each provides quay accommodation in pairs of lengths of 1,000, 600, and 400 feet successively, together with an end berth of 350 feet. The indentations permit of ships overlapping, while at the same time berths are afforded for small craft of 100 to 120 feet in length. A further advantage of the indentations is that moored vessels are well recessed out of the way of those passing in and out of the branches; in fact, provision is made for vessels being attended in their berths by rows of lighters on each side without obstructing the main waterway.

The sides of the branches, generally, are lined with sheds, from 100 to 120 feet in width, of varying lengths, and of heights taken at two storeys, but capable of adjustment to circumstances. The sheds are recessed 40 feet from the edge of the quay, to allow of lines for quay cranes and railway trucks. These lines, as well as others at the rear of the sheds, are all in inter-communication by means of a circular railway along the landward boundary of the estate, which is supposed to be connected with trunk lines. leading to other towns.

Special berths are provided at one branch dock for petroleum and coal, and at another for grain and timber. The petroleum berth has both tank storage and shed accommodation for barrels. The coal berth consists of an open quay, laid with numerous sidings and furnished with projecting jetties for hoists and tips. Grain is received direct into warehouses, the face line of which is within 5 feet of the edge of the coping. Timber may be discharged into a single storey shed or on to a low quay, or it may be floated

into the timber pond. The river frontage is also available for timber storage, as well as for a cattle wharf, if required, with a lairage at the rear.

There are four surplus plots of land, triangular in shape, between the branches. These can be utilised as sites, partly for administrative buildings and offices, and partly for warehouses and goods depôts, timber yards, and the like commercial adjuncts of a dock system. The land immediately adjoining the entrance locks will be advantageously occupied by the dockmaster's office and residence, and by dwellings for dock gatemen and other officials whose constant attendance upon the spot is desirable. A convenient site will also be found in the vicinity of the graving docks for a pumping station and, if hydraulic power is to be employed, for one or more accumulators, though possibly the requisite power may be as readily obtained from an external source, such as the mains of a private company or of a municipal body.

The design is an ideal one in this respect, that it presupposes an entire freedom of action in regard to site and outlay which is rarely attainable. There is nothing, however, to prevent the carrying out of the scheme partially or in instalments, as may be found necessary.

Ratio of Quay Space to Water Area. The ratio of quay space to water area will depend upon the relationship between the carrying capacity and the length of vessels which occupy berths in the dock in question. The following is an approximate statement of the nett registered tonnage of vessels per lineal foot, averaged from a considerable number of cases. It must be emphasised, however, that there is much variation dependent on the design of the vessel, whether for cargo solely or for cargo and passengers combined :

Vessels between 200 and 300 feet long, 5 to 6 tons per lineal foot.

Assuming a cubic equivalent of 40 feet to the ton, it is evident that the volume of space required for the reception of cargo will range between 200 cubic feet per lineal foot for small vessels and 600 cubic feet per lineal foot for large ships. This accommodation may be provided, either in open quay space or within covered sheds, in which latter case the available area will be doubled or trebled, if the shed have two or three storeys. But as goods will rarely be piled or stacked to a greater height than 10 feet, and as allowance must be made to the extent of 33 per cent. for alley ways and passages, it will probably be equitable to take an average of 5 feet in height over the whole surface. Accordingly, a superficies of from 40 to 120 feet per foot lineal will be required for the accommodation of cargo, but this is on the assumption that the whole is deposited upon the quay before the removal of any portion. On the other hand, no provision has been made for the simultaneous reception of outward-bound merchandise. The whole problem, in