What happens to the sand in a sieve? What does this have to do with Montag? What comparison does he make to the sand?

Part Two of the novel is entitled "The Sieve and the Sand," which metaphorically represents Montag's struggle to comprehend the texts that he is reading when he initially attempts to understand literature. While Montag is riding a subway train on his way to visit professor Faber, he attempts to read a passage out of the Bible but cannot focus or comprehend the texts because he is distracted by the extremely loud Denham's Dentrifice blaring through the train's speaker. Montag desperately attempts to read faster and faster in order to understand the texts, but his efforts are in vain.
Montag's inability to comprehend and remember what he has read reminds him of a time when he was a child and visited the beach with his cousin. Montag's cousin had bet him a dime that he could not fill a sieve with sand and Montag accepted the challenge. He proceeded to frantically fill the sieve with sand, only to watch it fall through the bottom. The sieve and the sand metaphor applies to the information Montag is attempting to comprehend, which he instantly forgets the second he reads a word because of the extremely distracting advertisements on the train.

When Montag was a child, his cousin said that if he could fill a sieve with sand, he would get a dime. Of course, Montag failed to get the dime because this task is impossible. The sand will always fall through the holes of the sieve, no matter how quickly it is filled.
When Montag travels to see Faber and is sitting on the subway, he remembers this incident with the sieve and the sand. With a Bible in his lap, he tries to memorize as much of the text as possible, just as he once tried to fill a sieve with sand.
The sieve and the sand, therefore, act as a metaphor in the novel. The sand is comparable to the literature he wants to memorize and understand. Conversely, the sieve is like his mind, desperately trying to retain as much information as possible.
The sieve and the sand also represent Montag's struggle to find meaning and happiness in his life. Just as he struggled to fill the sieve, the novel charts Montag's struggle to overcome the fireman system and erase censorship from his society.