The application of steam to the navigation of canals has long been considered a desideratum, and many plans have been brought forward for the purpose, but none have been permanently adopted. Amongst the obstacles to its introduction, is the swell caused by the propelling apparatus, which is so destructive to the banks, that unless it could be obviated, it would go far to counterbalance any advantages which might otherwise attend the use of steam. Another obstacle is found in the narrowness of the locks, which leave little space for the fixing of the propellers at the side of the vessel. On the other hand, canals admit of the application of modes of propelling, by which a fixed fulcrum can be obtained in lieu of the yielding or receding fulcrum which is afforded by the water.

Canal Navigation 617

We shall notice a few of the inventions designed especially for this object.