1. They built a primitive shelter out of tree trunks. 他们用一些树干建造了一个简陋的棚子.
2. After switching on powerful arc lights, they saw great stalagmites---- some of them over forty feet high ---- rising up like tree-trunks to meet the stalactites suspended from the roof. 他们打开强力弧光灯,看见一株株巨大的石笋,有的高达40英尺,像树干似地向上长着,与洞顶悬挂下来的钟乳石相接。