What is Elijah's Scalps?

The scalps that Elijah collects are a symbol for both his prowess as a sniper and his descent into madness. Elijah begins to collect these scalps after he meets the Frenchmen who tell him that he needs to take trophies of his kills. He takes them so that no one will ever to be able to contest his kills. The officers, mainly Breech, are constantly telling Elijah that they do not believe that he has killed the number of men he claims he has or that he has successfully taken a shot that he claims he did. The doubt they express in his ability makes Elijah angry. By collecting these scalps, he not only proves that he killed these men, no one can contest that he did not do what he says he did.