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of,) some directions will be given by which abridge may be more flexibly adapted to the mo-tion occasioned by a swell, in strong winds; aswell as to admit of the end boats taking theground in tide rivers; to neither of which is thepontoon bridge adapted. The balks are sobolted to each other, and the whole apparatus soframed together, that, excepting the little playwhich the bending of the balks may admit of,no pontoon can rise above, or fall below the levelof another, by the effect of a swell, withouteither bearing, or transferring from it, an undueportion of the weight then passing over. Pre-vented thus from rising with a wave, and at thesame time (from the shape of a pontoon) pre-senting a large end area to the current, this sortof bridge is not so easily anchored, nor, as boats,so dry, (and consequently more likely to befilled,) as in a bridge which admits of an undu-latory individual motion; and these are the chiefobjections to the use of pontoon bridges, in wideand rapid rivers.

This was abundantly proved in the passage ofthe Garonne at Grenade, in 1814, by the armyof the Duke of Wellington, previous to theBattle of Toulouse. That city served the enemyas a double tcte de pout. Its ancient walls werein a very defencible state, on both banks of the