as they loaded up again outside , the two chinese cooks , who had grown quiet and unhappy overnight despite not the least signs of homesickness over the whole course of their journey thus far , walked a little way off and each picked up a pebble and flung it at the wall , in what seemed to laurence an odd hostility : jing chao 's pebble bounced off , but the other , thrown by gong su , skittered and rolled down the sloping wall to the ground .