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
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. Simi