This innovation consists essentially in an arrangement by which two distinct vessels, on being revolved round their longitudinal axis to an angle of 90 deg., can be combined into one single duplex vessel, or, to put it in different words, a larger vessel is arranged so that it can be parted into two halves (called "semi-barges"), which can be used and navigated with equal facility as two distinct vessels, as if combined into one. By the combination of the two semi-barges into one duplex barge the draught of the vessel is nearly doubled, the ratio existing between the draught of a loaded semi-vessel and the equally loaded duplex vessels being 5:8 (up to 8.5) The advantage of the invention consists: 1. In this difference of draught. 2. In the smaller width of the semi-vessel as compared with the duplex vessel. 3. In the fact that the combination and separation of the vessels can be effected, without the least disturbance of the cargo, in a minimum of time. It facilitates the utilization, to the highest possible extent, of the varying conditions and dimensions of canal locks and rivers. The transition from rivers to canals, and from larger canals to smaller ones, is expedited by the possibility afforded of, on the arrival at the locks, dividing the vessel in a space of a few minutes; of passing with the semi-vessel, singly, the various smaller locks or the shallow canal, after which the two sections may be re-combined and navigated again as one vessel. The process of "folding up" the two vessels will of course take longer than that of separation. On rivers, the channels of which are interrupted by sand banks and rapids, the same operation may be carried out, thus avoiding the expense and delay necessitated by, perhaps, repeated "lightering," i.e., reduction of the cargo. Thus, the through traffic on large rivers like the Danube, with its repeated obstacles to navigation, such as the "iron gate," and several sand-banks known and dreaded by bargemen, would be materially facilitated, any necessity for unloading part of the cargo being obviated; moreover, such a duplex vessel composed of two semi-vessels affords the advantage of utilizing to a fuller degree the power of traction, and one large vessel will be more convenient for traffic than two smaller ones. Further, the mode of construction of the semi-vessels--both ends of which are of a similar pattern--allows of their being navigated up and down a water channel without the necessity of turning them round; provision having also been made for the fixing of the rudder at either end, which would therefore merely require exchanging. This is of some advantage in narrow river beds and canals, and applies equally to the duplex vessel as to the single semi-vessels. [Illustration: FIG. 1.] [Illustration: FIG. 2.] [Illustration: FIG. 3.] [Illustration: FIG. 4.] [Illustration: FIG. 5.]