How did Riddle Know?

[michaelkgidlow]

No: HPFGUIDX 71761

As I was finishing reading CoS, a thought occured to me. How did 
Riddle know that he was Slytherin's heir? Was he just interested in 
the legand of the CoS and went looking for it? His mother died at 
birth and his father certianly wouldn't have known. Or maybe he 
traced his linage, or discoved he could speak parseltongue or a 
combination of both. Humm...Any ideas?

Michael Gidlow