What does it mean that its recoil force+will bite the sand at the water-facing place under the stone as a pit?

Meaning: The recoil force of the current must erode the sand under the stone and form a pothole.

Source: Stone Beasts in the River by Ji Yun, a writer in the Qing Dynasty

Excerpt from the original text: An old river soldier heard of it and said with a smile: If a stone is lost in a river, it should be sought from the upper class. The cover stone is firm and heavy, and the sand is loose and floating, so the water can't wash the stone. Its counter-excitation force will bite the sand at the water-facing place under the stone, and it will gradually excite and deepen. When the stone is in the middle, the stone will fall into the pit. If you bite again, the stone will turn again. Turning around, I went back and forth. Seek the bottom, solid top; In the land of seeking, isn't it even more bumpy?

as he said, the fruit is miles away. However, it's a matter of the world, but knowing one, I don't know how many the other are, so can we make a reasonable assumption?

An old river soldier heard the lecturer's point of view and said with a smile: Any stone that falls into the river should be looked for in the upper reaches of the river. It is precisely because the stone is hard and heavy, and the sand is soft and frivolous, and the water can't wash away the stone. The recoil of the water must erode the sand under the stone to form a pit, and the more intense it is, the stone will be dumped in the pit when it reaches half of the stone.

if washed like this again, the stone will turn again. Keep turning like this, so instead of going upstream in the opposite direction. It is crazy to look for stone beasts in the lower reaches of the river; Isn't it crazier to look for stone beasts where they sank?

According to his words, the stone beast was found several miles (upstream). In this case, there are many cases where we only know superficial phenomena and don't know the fundamental truth. Can we judge subjectively according to a certain truth? Extended information

This article tells a fable with great educational significance, which expresses the author's ridicule for people who are ignorant and self-righteous, such as scholars, and also tells the characters that understanding things requires comprehensive and in-depth investigation and exploration. The full text has distinct levels, narrates around the search for stone beasts, and digs out the philosophy of life in the dramatic plot. The plot is simple and the language is concise, but it is intriguing to read.

This article tells a very instructive fable in concise language, praising the experienced old river soldiers, mocking the stupidity of monks and satirizing the self-righteousness of Confucianism and Taoism. It has great enlightenment and guiding significance for people's thinking and understanding.

The full text has a clear hierarchy, and its writing structure mainly focuses on the search for stone beasts, and excavates the philosophy in life in dramatic plots. Monks in the temple, like ordinary people, because of their limited knowledge of external things, rowed a few boats according to conventional thinking and searched for stone beasts along the river, of course, they could not find them.

However, it is not correct for a scholar to reason according to the knowledge he has learned from books. His theory may convince everyone temporarily, but the fact is still the fact. If you dig underground according to the scholar's theory and method, you will certainly not find stone beasts.

Because he has been dealing with rivers all the year round, he has a more detailed understanding of the habits of water, stone and sediment in rivers, so he can draw a correct conclusion: the stone is going upstream. Looking upstream according to the method of the old river soldier, I found the stone beast.

About the author: Ji Yun (1724-185), whose name is Xiaolan, whose name is Chunfan, whose name is Shi Yun, whose name is Guanyi Taoist, was born in xian county, Zhili (now Cangzhou, Hebei). Politicians and writers in Qing Dynasty, officials in Qianlong period. Li Guan left the capital for the suggestion, the Ministry of War, the Ministry of Rites, the co-organizer, the college students and the Prince Taibao were in charge of imperial academy affairs, and he was the chief editor of Sikuquanshu. Ji Yun studied Confucianism, read widely, wrote poems and parallel prose, and was especially good at textual research and exegesis.