He sat on heavily, looking out over his land. If he had his buffalo back, if he had his plow that they had burned for fuel, he could plow the land. But when he thought of this as he did many times every day, he felt helpless as a leaf tossed upon the flood. The buffalo was gone; gone also his plow and every implement of wood and bamboo, and what other had he? Sometimes in the winter he had felt grateful that at least the flood had not taken all the house as it had so many other houses. But now suddenly it came to him that he could be grateful for nothing, no, not even that he had his life left him and the life of his wife and the two older children. He felt tears come into his eyes slowly as they had not even come when he buried his old mother and saw the earth fall against her flesh, bared by the rags which had comforted him that day. But now he was comforted by nothing. He muttered to himself.
(出自《贫瘠的春天》)
请问老师这一段落中的 sit on是什么意思?查阅牛津词典,发现 on 作为副词的义项中没有一个符合文意的,就算是表示持续性动作的这个义项,也不适合于猛地坐下这个突然的动作。所以想问问尊敬的老师,这个词组是什么意思。