In chapter two what episodes reveal a streak of violence in Jack in Lord of the Flies?

Jack's violent nature is foreshadowed in Chapter 2 through
several incidents.  At the very first meeting, the boys agree to vote on a chief as well
as to establish rules.  Jack announces:

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"We'll have rules! Lots of rules! Then when
anyone breaks 'em--" 

Here we
see Jack is more excited about punishing those who break the rules than the rules
themselves. 

When the boys attempt to build a fire, it is
Jack who forcibly takes Piggy's glasses to use to start the
fire. 

"Later, when the question of a snake-thing or beast
arises, Ralph quickly denies that there is a beast.  Jack agrees with Ralph, but he
adds,

"There
isn't a snake-thing.  But if there was a snake we'd hunt and kill
it." 

These three examples
show a violent streak in Jack that intensifies throughout the
novel.