deceased was riding on the buffer of the fore-end of the front wagon of a train of six, which were being pushed round a curve, of a radius of 5½ chains, to the quarry face; the truck was derailed and travelled about 7 yards over the ballast and sleepers before it was stopped; just prior to the truck stopping deceased lost his hold and was jerked off, and falling head foremost on to the ground his neck was dislocated, and he was killed instantly; the road was apparently well laid, and no defect could he found to account for the derailment of the truck