But to return to our rabbits. The rabbits are turned into a source of revenue by the farmers. They increase so rapidly that their numbers have to be kept in check. Sometimes a farmer will sell the "rabbiting" on his farm for the season, for £50 or so, just as the "shooting" is let. Then the rabbit-catcher makes what he can out of it. At other times the farmer will pay the rabbit-catcher so much for every couple caught, and then sell them at a profit. I have known fifty-seven couple to be caught by one man in a day on Sewingshields Crags. You need to look well to your walking when the rabbit-catcher is abroad, for of course he makes his loops of wire as invisible as possible, and you would certainly be brought to the ground if you put your foot in one of them. I was very glad that I never came across a rabbit in a trap, though I used to see hundreds of traps. A shepherd told me that once he saw a pathetic sight: a rabbit in a trap, still feeding her young ones. Missing her, they had crept up out of the burrow, and had traced her to the trap. He set her free at once, for she was not hurt. This has been a long delay on our walk, but it is so hot that to sit and watch the rabbits will have done us all good. {115} There used to be a castle, known as Sewingshields Castle, in the fields to the north, built there, it is supposed, to defend this pass of Cat Gate. The field where it stood is still known as "The Castle." Continuing along the crags, I soon came to the site of another mile-castle. All along here the Wall is in a very ruinous condition, but one can follow closely the mound which once was Wall. Before leaving the Sewingshields region, we see ahead an important gap called Busy Gap. Here the Wall bends nearly southward, in order to avoid Broomlee Lough (which laps the feet of Sewingshields Crags) and to make for the next line of crags. Nothing but the foundations remain of the actual Wall, but stones are piled up roughly on them to make a field-boundary. It is the interval between the end of Sewingshields Crags and the beginning of the Housesteads series which is known as "Busy Gap," for it was a very weak place on the Wall, and the enemy knew it. Besides digging the usual Wall-ditch across the gap, the Romans made an earthern rampart, triangular in form, as an additional protection. Camden says of this Gap in 1599: "I could not with safetie take the full Survey of it for the ranke-robbers thereabout." One evening when I was returning home from {116} this spot, quite suddenly the mist came down, and blotted everything out. I could not even see the ground at my feet, and anyhow there is no path to follow. So the only thing I could do was to strike upwards until I came to the mound of the Wall on the top of the crags, and then to keep along its south side. After a while the mist lifted as suddenly as it had come down, and I found myself within a stone's-throw of the little plantation at Sewingshields.