Why leave the book?

[spotsgal]

No: HPFGUIDX 136984

Potioncat:
> Snape is surprised that Harry is doing well in Potions. But he is 
> furious that Harry knows the sectumsempra spell. He demands to know 
> where Harry learned it. Later he is angry that his spells are being 
> used against him. Clearly, Snape never intended any student to get 
> ahold of the book.

Christina:
I totally agree, and I just wanted to add in the bit of canon that
convinced me that Snape didn't know that Harry had his book:

(HBP, US, page 319)
"...Some credit must go to you, of course, you tuaght him for five
years!"
Trapped, with Slughorn's arm around his shoulders, Snape looked down
his hooked nose at Harry his black eyes narrowed.
"Funny, I never had the impression that I managed to teach Potter
anything at all."
"..<snip>...You should have seen what he gave me, first lesson,
Draught of Living Death-- never had a student produce finer on a first
attempt, I don't think even you, Severus--"
"Really?" said Snape quietly, his eyes still boring into Harry, who
felt a certain disquiet.
(end quote)

The passage begins with Snape acting his usual "Yeah, doesn't Potter
think he's so awesome?" self, but as soon as Slughorn gives a specific
example, proving Harry's abilities, Snape goes quiet and his eyes
"bore" into Harry.  The moment passes and Slughorn brings up
Auror!Harry, and Snape falls back into his usual sneer.  The
Sectumsempra part is great too- Snape speaks to Harry "quietly" and
"softly" - he seems so angry I got shivers when I first read it.


Potioncat:
> He also says that James used his spells. If the spells are non
> verbal, how did James learn them?  I think someone found/took the 
> book and used the spells, perhaps sharing them with his best
friend. 

Christina:
We agree again.  I definitely think the Marauders got their hands on
the book somehow, slipping it into the Potions cabinet when they were
done with it.

Potioncat:
> The biggest hole in my idea, is that James knew the Levicorpus spell
> in 5th year. That seems too early for the book to go missing.

Christina:
Actually, I don't think that Snape made those notes in his NEWT year.
 Sirius says that Snape knew more hexes and such coming into Hogwarts
his first year than most of the seventh years did.  Snape must have
had an eager tutor and/or loads of books at home (I'm betting on the
books at least, considering the fact that his walls of books at
Spinner's End shows his love for reading).  We know that the Potions
book was old enough to have been used by Snape's mother when she was
in school.  I can totally imagine a scenario where Snape is given the
book to study (and eventually use as a hand-me-down) long before his
sixth year.  If he was wholly self-taught, he could have stumbled upon
the book on his own in his family's library.  Maybe Slughorn even saw
potential in young Snape from the start, saw he was bored in class,
and gave him a higher-level book for a little enrichment reading. 
Teachers did that all the time at my elementary school.


Christina