Each semi-barge on its part is also constructed of two equal
halves--which are, however, inseparable--and as there is no distinct
stem or stern, any one of these semi-vessels will fit any other
semi-vessels of the same dimensions, and can be attached to the same
by means of the coupling apparatus, and the two "folded up" into one
duplex vessel. This process does not present any material
difficulties. The two single boats on being coupled together can be
made to lean over toward each other, by filling their lateral water
compartments, to such an extent that the further closing up can be
easily effected by means of specially constructed windlasses. In the
case of petroleum vessels the "folding up" operation is facilitated by
the circumstance that the petroleum may be made to serve the purposes
of water ballast.

As regards the size and tonnage of the new vessels, this will of
course depend on the local condition of the rivers and canals to be
navigated. Thus a vessel destined for traffic on canals with locks of
varying dimensions will have to be adapted to the dimensions of the
smallest existing lock.

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