《徐霞客游记·黔游日记二》
在坡路积水处，有泉水泊泪从地下溢出，泉眼大如手指，用手指伸进泉眼，都是沙土，随着手指插进去水就变混浊了，指头抽出便又溢成孔洞，这是气体上升的机理使沙土流动，而泉水随着气体冒出来，没有固定的洞穴。
当坡路潦小水塘迹间，有泉泛泛从下溢起，孔大如指，以指探之，皆沙土随指而溷ｈùｎ混浊，指去而复溢成孔，乃气机所动，而水随之，非有定穴也。
In the water-filled area of the slope, spring water broke out from underground, the spring was as big as a finger, and when a finger was inserted into the spring, it was all sand, and the water became muddy as the finger was inserted, and the finger was withdrawn and the hole overflowed again. This is the mechanism that gas rises and the sand flows, and the spring water gushes out with the gas, without a fixed cave.