The third sentence "Flying down three thousands of feet" is a detailed description of the waterfall at close range. "Flying Flow" shows that waterfalls come out in the air and spew out. "Straight down" not only describes the steepness of the rock wall, but also describes the rapidity of the water flow. "Three thousands of feet" is an exaggeration, describing the towering mountains.
In this way, the poet felt that the majestic momentum of the waterfall had not been fully displayed, so he went on to write a sentence, "It is suspected that the Milky Way has fallen for nine days." It is said that this waterfall "flew down", which makes people suspect that the Milky Way poured down from nine days. A "doubt" is ethereal and lively. If it is true, it makes people daydream, which adds to the magical color of the waterfall.
This poem is very successful in metaphor, exaggeration and imagination, with unique conception, vivid language and bright washing. Su Dongpo appreciates this poem very much, saying that "the emperor sent the Milky Way to fall into the pulse, and there were fallen immortals in ancient times." The "immortal" is Li Bai. Looking at Lushan Waterfall is indeed an example of body description and lyricism.