left - Anti-breakage box used in shipping coal at Penarth Dock, Taff Vale Railway. [479]

The South Wales steam-coal, however, is very fragile, and to give a drop of forty-five feet would damage it seriously. Accordingly a most ingenious intermediary, in the form of an " anti-breakage box, " has been devised, which is lowered down by a crane to receive the coal at the foot of the shoot, and in which the coal is further lowered until it is in close proximity to the hold of the vessel. This box is made in two parts, so arranged that it opens automatically by the tightening of a chain at a certain stage in the operation of lowering, and close automatically when raised. The use of the box can be dispensed with after part of the cargo has been loaded, and the heap of coal rising in the hold itself serves to break the force of the fall from the shoot.

When all four moveable tips at Penarth are concentrated upon a single vessel, four ten-ton coal wagons can, in the space of thirty seconds, be lifted from the quay, their contents tipped into the shoot, and the empty wagons brought back to quay level. But the operations of feeding the cradle with wagons from the siding on the quay, and boxing and trimming the coal as it falls from the shoot, make it impossible to ship the whole cargo at the maximum speed of the tips themselves. The results obtained are, nevertheless, very remarkable. On one occasion a vessel took in 2,333 tons in one hour fifty-five minutes, 1,430 tons being shipped in the first hour, or at a rate of nearly twenty-four tons a minute.

At other parts of the dock, when the conditions allow high-level tips to be used, and it is not necessary to raise the wagons by hydraulic power before tipping them, an even greater amount of work can be done per tip. But high-level tips are necessarily fixed ; the advantage of the low-level ones is that they are moveable, and the whole four at Penarth can be concentrated on to a single vessel. [479]