By noontime the soldiers' clothes were wet through with sweat, and the marching speed slowed down. Some soldiers of weak physique even fainted on the roadside.

到了中午时分，士兵的衣服都湿透了，行军的速度也慢下来，有几个体弱的士兵竟晕倒在路边。

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It's a device used to measure the speed of marching troops by counting the number of paces taken each minute.

FORBES: Magazine Article