It USES a thin stream of falling sand to measure time.
它使用一小股落下的沙子来计算时间。
Sand and leaves trapped the water in the stream.
沙子和树叶堵住了小河的水流。
The stream had washed (out) a channel in the sand.
小河在沙地上冲出了一条沟。
The stream had washed a channel in the sand.
小河在沙地上冲出了一条沟。
The stream had washed a channel in the sand.
小河在沙地上冲出了一条沟。
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