There comes next the important matter of detail as to the way in which coal brought to a port is to be shipped. Nothing could be simpler and more expeditious than the practice generally adopted in the case of rail-borne coal. When a given quantity of coal is to be despatched, the vessel is brought alongside a hydraulic coal-tip, such as that shown in the illustration facing this page, and the loaded coal trucks are placed in succession underneath the tip. Raised one by one to the level of the shoot, the trucks are there inclined to such an angle that the entire contents fall on to the shoot, and thence into the hold of the ship. Brought to the horizontal again, the empty truck passes on to a viaduct, down which it goes, by gravitation, back to the sidings, the place it has vacated on the tip being at once taken by another loaded truck. [Illustration: THE SHIPPING OF COAL: HYDRAULIC TIP ON G.W.R., SWANSEA. (The loaded truck is hoisted to level of shoot, and is there inclined to necessary angle to "tip" the coal, which falls from shoot into hold of vessel. Empty truck passes by gravitation along viaduct, on left, to sidings.) [_To face page 88._ ] Substitute coal barges for coal trucks, and how will the loading then be accomplished? Under any possible circumstances it would take longer to put a series of canal barges alongside a vessel in the dock than to place a series of coal trucks under the tip on shore. Nor could the canal barge itself be raised to the level of a shoot, and have its contents tipped bodily into the collier. What was done in the South Wales district by one colliery some years ago was to load up a barge with iron tubs, or boxes, filled with coal, and placed in pairs from end to end. In dock one of these would be lifted out of the barge by a crane, and lowered into the hold, where the bottom would be knocked out, the emptied tub being then replaced in the barge by the crane, and the next one to it raised in turn. But, apart from the other considerations already presented, this system of shipment was found more costly than the direct tipping of railway trucks, and was consequently abandoned. Although, therefore, in theory coal would appear to be an ideal commodity for transport by canal, in actual practice it is found that rail transport is both more convenient and more economical, and certainly much better adapted to the exigences of present day trade in general, in the case alike of domestic coal and of coal for shipment. Whether or not the country would be warranted in going to a heavy expense for canal resuscitation for the special benefit of a limited number of traders having works or factories alongside canal banks is a wholly different question.