how does the time travler find out about the past and how the morlocks and eloi came to be the way they are?

Are you sure this is a Chapter Nine question?

`So, as I see it, the Upperworld man had drifted towards his feeble prettiness,

and the Underworld to mere mechanical industry. But that perfect state had

lacked one thing even for mechanical perfection|absolute permanency. Apparently as time went on, the feeding of the Underworld, however it was elected,had become disjointed. Mother Necessity, who had been staved off for a few thousand years, came back again, and she began below. The Underworld be-ing in contact with machinery, which, however perfect, still needs some littlethought outside habit, had probably retained perforce rather more initiative, if less of every other human character, than the upper. And when other meat failed them, they turned to what old habit had hitherto forbidden. So I say I saw it in my last view of the world of Eight Hundred and Two Thousand Seven Hundred and One. It may be as wrong an explanation as mortal wit could invent. It is how the thing shaped itself to me, and as that I give it to you."

This was from Chapter Ten.