"Please, sir, don't legends always have a basis in fact?"
-- Hermione Granger
HRH are questioned about the Petrified cat, Hermione asks Professor Binns about the Chamber of Secrets, HRH return to the scene of the crime, consult Moaning Myrtle, and speculate about the mystery.
Calendar and Dates
The action of this chapter picks up on Hallowe'en night, and covers the next few days.
Interesting facts and notes
This chapter gives us our first close look at a History of Magic lesson, and at Professor Binns, Hogwarts' only ghost teacher.
"I remember something very similar happening in Ouagadougou," said Lockhart, "a series of attacks, the full story's in my autobiography."
That is, the story is in Magical Me. Ouagadougou is a real place, the capital of Burkina Faso, a country in western Africa noted (in the wizarding world) for the fact that runespoors originate there.
A clock chimed somewhere.
"Midnight," said Harry.
See The Number Twelve.
Professor Binns had asked for a three-foot-long composition on "The Medieval Assembly of European Wizards".
Apparently this way of setting the length of a writing assignment is typical of Hogwarts teachers in general. Since the students use parchment rather than paper, the teachers do not set assignments in terms of the number of pages to be written, but by the length of the roll of parchment to be used.
This leads to an awkward question. How can Professor Binns collect homework assignments, let alone handle the rolls of parchment to open them up and read them?
Professor Binns opened his notes...
If these were tangible, ordinary notes, Binns wouldn't be able to enter the History of Magic classroom through the wall without leaving them behind. So they must really be "ghosts" of a sort in their own right. Possibly they're something similar to the rejection letter that Nearly Headless Nick received from the leader of the Headless Hunt (CS08).
...and began to read in a flat, drone like an old vacuum cleaner until nearly everyone in the class was in a deep stupor...
It isn't that Binns' subject matter is necessarily dull that sabotages the students' education in History of Magic. It's a combination of several things, and Binns' droning voice is the least of them. The main difficulty is that Binns reads from his notes, without trying to prod the class into participating. Since he doesn't ask them questions, they tune him out.
He had been speaking for half an hour when something happened that had never happened before. Hermione put up her hand.
Interesting that even Hermione has never bothered to speak up in History of Magic before. In fact, this is one of the very, very few occasions in Hermione's first five years at Hogwarts when she has participated in class by asking a question to try to learn something rather than by volunteering the answer to a question the teacher has asked.
Professor Binns, glancing up in the middle of a deadly dull lecture on the International Warlock Convention of 1289, looked amazed.
This may not be related to the subject of the homework that Harry, Ron, and Hermione handed in during the same class. Hogwarts teachers seem to assign homework based on the current lecture's topic, not the topic of an upcoming lecture, so the homework most likely relates to whatever Binns was lecturing on ten days ago, when the essay was assigned.
"My subject is History of Magic," he said in his dry, wheezy voice. "I deal with facts, Miss Granger, not myths and legends."
This is a quite interesting attitude for a wizarding person to take, suggesting that Binns is an historian first and foremost before any considerations of being a wizard (or the ghost of a wizard).
"In September of that year, a sub-committee of Sardinian sorcerers..."
That is, September of 1289, presumably. Sardinia is an island that in the modern world is part of Italy.
He cleared his throat with a small noise like chalk snapping
Nicely implying a quiet, dry, academic sort of noise.
Professor Binns was looking at her in such amazement, Harry was sure no student had ever interrupted him before, alive or dead.
If true, no wonder Professor Binns has almost given up on the students; he hasn't had any who care about the study of history, and apparently doesn't know how to inspire an interest in his own subject.
But the whole class was now hanging on Professor Binns' every word. He looked dimly at them all, every face turned to his. Harry could tell that he was completely thrown by such an unusual show of interest.
Notice that once the students begin actively participating in class, Binns turns out to be able to tell quite a good story.
"You've used spiders in potions loads of times..."
Consequently, we know that dead spiders are a potion ingredient, although we don't know of any specific potions that use them.
"If you must know, when I was three, Fred turned my - my teddy bear into a dirty great spider because I broke his toy broomstick."
So wizarding children have the same kinds of toys that Muggle children have - such as teddy bears - as well as more magical toys such as toy broomsticks. We'll see more examples of what small children in the wizarding world play with at the Quidditch World Cup campgrounds, nearly two years from now.
"Five points from Gryffindor!" Percy said tersely, fingering his prefect badge.
This remark has led to a great deal of correspondence, since in OP the prefects told Draco Malfoy that prefects could not take House points.
There was only one way to get out a book from the Restricted Section: you needed a signed note of permission from a teacher.
After Harry's experiences in his first year, this is certainly a better bet than illicitly sneaking in there under an invisibility cloak.
Exceptional character moments
Binns, who (according to rumour) never noticed when he died, but simply got up from his armchair, leaving his body behind him, and hasn't varied his routine in the slightest since. There is someone who is focused.
Binns, who is obviously unused to anyone in his class actually being a student of history and taking an interest in his subject. Once the students take an interest in his material (which completely throws Binns), he reveals an unsuspected ability to relate history as a story.
Binns' annoyance at the idea of anyone believing such a story as the legend of the Chamber of Secrets, when there is no reliable evidence to support it and when various searches of the castle seem to provide evidence that it doesn't exist. Binns is the sort of person who has both feet firmly on the ground, so to speak; he is concerned with concrete evidence rather than imaginative theories.
Filch, who breaks down crying when he believes that Mrs. Norris is dead.
Ginny, who is a great cat-lover.
Lockhart. Even photographs of him are so vain that they put their hair up in rollers and hairnets at night.
Ron, who has been arachnophobic since the age of three, when Fred Transfigured Ron's teddy bear into a spider while Ron was holding it.
"D'you think we've got nothing better to do in Potions than listen to Snape?" muttered Ron.