The Power of Fire

"The seizure of the station with a fit of trembling, gradually deepening to a complaint of the heart, announced the train. Fire, and steam, and smoke, and a red light; a hiss, a crash, a bell, and a shriek; Louisa put into one carriage, Mrs Sparsit put into another: the little station a desert speck in the thunder-storm."

Rather than passively observing the fire as she did in Book One, Louisa has now internalized the fire for her own benefit. It is her fuel, as it is the train's. Dickens lists the elements that comprise the train's arrival in quick succession to create a chaotically layered image which mirrors Louisa's emotional state. Fire transports her to her final destination, to confrontation, to her emotional destruction. Steam--a byproduct of fire--is especially significant here, because it represents Louisa's once-dormant emotions building inside of her: an internal force, ready to burn whomever it is unleashed upon. Her breakdown at the end of Book Two is Gradgrind's karmic retribution for repressing her fire for so long; however, because he is burned by the fire he once extinguished, he ultimately reforms his character.

DISCLAIMER: If Google brought you here because you're doing an assignment like this: this is not a credible source. At all. Have fun suffering through Hard Times ("suffering through hard times"<---Lololol) with only whatever Google is showing you. :D
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(Would a credible source end a blog post with :D? Nope.)