To make what follows clear, it is necessary to describe this covered-way a little more in detail. It has already been explained that it formed the approach to an opening in the rock--closed by gates--which was the principal entrance to Coryon's retreat. When unprotected by the sliding gratings at the side, it was so near to the great devil-tree that the longer branches could sweep its whole width for some distance in front of the gates. At the side was some masonry, above which the rock rose steep and almost over-hanging. At the end, above the entrance, the rock rose also abruptly, and then followed the line of the arena, shutting in the latter at this part by a rocky wall that rose perpendicularly some fifty or sixty feet. But the part within reach of the tree was roofed over by iron gratings, forming a sort of verandah, which, in turn, could be rendered safe from the terrible branches by sliding grated doors or shutters that could, by machinery within, be moved forward in telescopic fashion along the whole length accessible to the tree, and a short distance beyond. Thus, when the side 'shutters' were withdrawn, the entrance-gates were very effectually guarded by the tree itself. When they were extended, they, in conjunction with the roof, constituted an efficient protection to the covered-way. But herein lay also a cunningly-devised and deadly trap; for, just within the entrance of this covered-gallery, was another iron door that could be moved across the passage so as to imprison any one caught between it and the gates at the other end. This door came out of a scarcely noticeable slot in the masonry at the side; and it was situated far enough along to place those thus caught within reach of the tree, if the side shutters were withdrawn. Doubtless, many had fallen into this frightful trap. Thinking the gallery well protected they would walk unsuspiciously along it towards the closed gates, when those watching from within could close the gallery behind them and open the sides; and their fate would then be sealed. This was the only part of the main terrace within reach of the tree. Round the remainder of the amphitheatre it was far removed from it, and was of ample width. Only at this part, and upon the stone pier that jutted out towards the tree from the centre, or down in the arena itself, was there danger to any one moving about within the vast enclosure. At a point in the cliff, high above the covered-way, was a small grated door in the rock. This was another entrance to Coryon's fastness; but it was sufficiently protected by the nature of the steep and narrow path by which alone it could be reached.