Every ten billion years one single grain of sand falls to the bottom.

每100亿年才会有一粒沙掉落到沙漏下方。

" I was careless." She shrugged, feeling caked sand fall away from her robe.

“我粗心。”她耸了耸肩，感觉到结块的沙子从她的长袍上掉落。

Every compartment seemed to have sand falling into it from the compartment above, through a small hole.

每个隔间似乎都有沙子从上面的隔间通过一个小孔落入其中。

She dug down four more layers, hoping that was deep enough to avoid pockets of sand falling from above.

她又挖了四层， 希望足够深， 以免沙袋从上面掉下来。