They set out; after a run of two leagues, Musqueton's horse sank.

The horses sank their heads low and panted rhythmically.

Even as they rode at each other, the horse of Tarascus sobbed and sank under him.

The horse sank another two feet, and the barn echoed with Sweetpea's cries.

He heard the horses sink under their weight, wallow about and whicker indignantly.

The horse sank fetlock-deep, and each of his hoofs made a sucking sound as it was pulled from the half-thawed ground.

Within a few seconds, the horse sank below the cauldron's rim.

Like the piece beside it, it proved treacherous, and the horse sank into mud again.

He started for the far shore but got only half way when his horses again sank in quicksand and one fell.

But then the horses sank below some unseen boundary layer like a thermocline, and the cold began to dissipate.