Because light traveling down from a summit passes through many such layers, a surveyor could sight a mirage rather than the peak itself.
因为从山顶向下传播的光会穿过许多这样的层，所以测量员看到的可能是海市蜃楼而不是山峰本身。
2
When he grew older, William Smith taught himself surveying from books he bought with his small savings, and at the age of eighteen he was apprenticed to a surveyor of the local parish.