Supposing the size of the latter to be such as found in the case of the Rhine-Marne or the Rhine-Rhone Canal, or on the Neckar down to Cannstadt, or in the Danube-Main Canal and some smaller canals in the Weser district, etc., viz.: 

Length of lock     34.5 meters. 
Width               5.2   "
Depth               1.6 to 2.0 meters.

The semi-barge may be made 32 meters in length, 4 meters in breadth and 2.5 meters total depth, and with a draught of 1.5 meters will be capable of carrying a load of 100 tons (of 1,000 kilos each).  Correspondingly the duplex vessel will be able to carry 200 tons, with a minimum draught of 2.4 meters and a width of 5.4 meters, but, with a favorable height of the water level, the draught of the semi-barge may be increased to 1.65 and that of duplex vessels to 2.7 meters.

Where not limited to certain proportions by the dimensions of the locks to be passed, the vessel may in the first place be made longer; the width and height may also be increased accordingly (provided that the proportion of breadth to width is kept within the ratio 4:2.5), so that the semi-barges may be constructed for a single burden up to 300 tons, or 600 for the duplex vessel.

As regards the nature of the cargo, parcels would not be admissible in this instance, but any kind of homogeneous cargo would be suitable which would bear laying over on one side.

Thus this style of vessel would be well adapted for petroleum tank vessels, for the transport of all kinds of cereals, flour, coffee, and sugar in sacks—­these latter being held in position by an arrangement of planking and boards so as to prevent any overturning of the goods on the vessels being folded up or taken apart.  Similarly in the case of a cargo of loose grain or other loose produce, the same must be prevented from being upset by a kind of wooden casing.

Two semi-vessels loaded with different cargoes may be coupled together, provided that there is not too much difference between their respective draughts.  Slight differences may be balanced by the water compartments being filled to a greater or smaller extent.

The peculiar position of the hatches allows of loading the semi-vessels separately as well as when coupled together.

If there is for the time being no necessity for using the vessels in their capacity of separate and duplex barges, any kind of cargo might be loaded that does not require large hatches.

The vessels, on account of their more complicated construction, will be somewhat more expensive, but wherever the advantage offered by them outweighs the extra expenditure, they can be used with success.

The innovation might be of particular importance where a new canal system is being constructed, since the latter might be subdivided into main canals and branch canals—­similarly as in the case of ordinary and narrow gauge railways—­the main canal being built of a larger section and with larger locks to suit the duplex barges, while the branch canals could be planned of smaller dimensions calculated to suit the semi-barge.  Thus the first cost of such a canal system would be materially reduced as compared with a canal installation of one uniform section throughout.