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can lead to a safe settlement of the particulardescription, shape, and dimensions of pontoonsor bateaux, most proper for military bridges.In point of safety from being filled by the surgesand wash of swells and rapids, cylindrical pon-toons, as close vessels, are highly advantageous;but in shape they are very defective in the im-portant qualities of steadiness of bearing, andstability. They are, however, preferable, uponthe whole, to pontoons as they are at present;but then these are very defective and dangerousvessels. From the preceding principles andcomparative statements, the question appearsto be, whether the principle of safety ( inacces-sibility to water), which would lead us to preferthe close vessel, might not be obtained insome other manner and shape, more favourableto increasing bearing, stability, and the otherproperties which all floating vessels should bemade to possess.

Inflated bags, made of animal skins, displacegreat bulks of water, compared with theirweight, and may therefore be considered usefulexpedients for forming rafts, or for giving ad-ditional buoyancy to those formed of otherbodies. The suggestion made to Xenophon bythe Rhodian, thus to endeavour to pass theTigris, is well known. Alexander adopted this

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