But many ways of storming a castle were discovered. They could be scaled by means of tall ladders, especially in a stealthy night attack. Stones could be thrown over the walls by mangonels to annoy the garrison. Sometimes a wall could be brought down by a battering-ram. But the quickest and surest way was by mining. The miners worked their way to the wall, and then began to take some of the stones of the outer casing out, propping the wall up with beams of wood. When the hole was big enough, they filled it with firewood; they greased the beams well, they set fire to them and then retired to a safe distance to see what happened. When the great wall crashed down, the soldiers swarmed over it to beat down the resistance of the garrison. If ever you go to Abergavenny Castle, in the Vale of Usk, look at the cleft in the rock along which the daring besiegers once climbed. And if you go to the Vale of Towy, and see Dryslwyn Castle, remember that the wall once came down before the miners expected, and that many men were crushed. In order to prevent mining, many changes were made. Moats were dug round the castle, and filled with water. Brattices were made along the top of the towers, galleries through the floor of which the defenders could pour boiling pitch on the besiegers. The walls were built at such angles that a window, with archers posted behind it, could command each wall. Stronger towers were built—round towers with a coping at each storey, solid as a rock, which would crack and lean without falling; there is a leaning tower at Caerphilly Castle. One other way I must mention—the child or the wife of the castellan would be brought before the walls, and hanged before his eyes unless he opened the gates. The newer or Edwardian castles, those of the reigns of Henry III. and Edward I., are concentric—that is, there are several castles in one; so that the besiegers, when they had taken one castle, found themselves face to face with another, still stronger, perhaps, inside it. Of these castles, the most elaborate is the castle of Caerphilly, built by Gilbert de Clare, the Red Earl of Gloucester who helped Edward in the Welsh wars. And it was by means of these magnificent concentric castles—Conway, Beaumaris, Carnarvon, and Harlech—that Edward hoped to keep Wales. There are many kinds of bows. In war two were used—the cross-bow and the long-bow. The cross-bow was meant at first for the defence of towns, like Genoa or the towns of Castile. So strength was more important than lightness, and the archer had time to take aim. It was a bow on a cross piece of wood, along which the string was drawn back peg after peg by mechanism. The bow was then held to the breast, and the arrow let off. It was clumsy, heavy, and expensive.