“Sometimes more than a thousand, ” he wrote, “in anamount of material the size of a grain of sand.”
他写道，“有时一粒沙子大小的样本中就有超过一千的微生物。”
2
As these rise, they latch on to dust in the air and become particulates, a quarter the size of a grain of sand.
上升过程中，这些元素附着在空气中的尘埃上，变成微粒，大小相当于一粒砂子的四分之一。
3
The oyster dutifully coats the little marble with anouter layer of pearl and much time is saved not having to grow each pearl upfrom the size of a sandgrain.