I hit her such a fourpenny one that I sent her flying.

我拳把她打飞。

One day,he took me aside and promised me a sliver fourpenny on the first of every month if I would keep my eye open for a sailor with one leg and let him know the moment he appeared.

有天他把我拉到边，向我保证每月给我四便士，如果我能留心注意个只有条腿的手，且在他（手）出现的那刻告诉他。