The stamping beast

In the reading due for tomorrow, there is a striking repetition of the image of a beast stamping on the beach. On page 4 Louis says: "I hear something stamping,"[...]"A great beast's foot is chained. It stamps, and stamps, and stamps." On the next page he repeats: "The beast stamps; the elephant with its foot chained; the great brute on the beach stamps,"[...]. This image is repeated towards the end of tomorrow's section on page 41: "[...] but I hear always the sullen thud of the waves; and the chained beast stamps on the beach. It stamps and stamps."
I think that the image of the elephant or beast stamping on the beach is just a metaphor for the noise waves make when they hit land (especially the last example makes that pretty clear). It also implies that waves, as a force of nature, cannot be tamed. The repetition of "stamps" shows the continuity. The waves never stop hitting the land because the sea is always in motion.
It is, however, interesting that an unusual metaphor like this appears so often in the book.
Louis seems to associate the sound of the waves with his childhood/schoolyears. Probably the thudding of the waves was unknown to him when he first came to England as a child. His first, imaginative explanation for the sound may thus have been an elephant stamping. That is why he returns to this metaphor when thinking about the waves (and his childhood).