How we cite our quotes: (Chapter. Paragraph)
Quote #7
The young heir glanced round with a gloomy face.
"It's no wonder my uncle felt as if trouble were coming on him in such a place as this," said he.
"It's enough to scare any man. I'll have a row of electric lamps up here inside of six months, and you won't know it again, with a thousand candle-power Swan and Edison right here in front of the hall door." (6.41-3)
So much for Sir Henry's exclamation of delight. As soon as he gets to his new home, he's creeped out. His plan to light up Baskerville Hall lets us know that this whole area is basically stuck in the past. With his New World background and interest in newfangled technologies, Sir Henry represents a reforming spirit, wanting to bring Baskerville Hall into the brand-new 20th century.
Swan and Edison was the local electric company at the time. The general availability of electrical power was so new and exciting that we doubt that parents were yelling at their kids to turn off the lights, for Pete's sake.
Quote #8
The whole steep slope was covered with gray circular rings of stone, a score of them at least.
"What are they? Sheep-pens?"
"No, they are the homes of our worthy ancestors. Prehistoric man lived thickly on the moor, and as no one in particular has lived there since, we find all his little arrangements exactly as he left them..." (7.82-3)
The history of Dartmoor is literally written on the ground. With all these architectural ruins, we can never forget that The Hound of the Baskervilles strongly associates the moors with the past and prehistory of England. We can compare this with the London of the earlier chapters, where everything's shiny and new. Early 20th-century London was a place where new stuff was constantly being built: hotels, theaters, subways, and department stores (source).
Quote #9
To that Providence, my sons, I hereby commend you, and I counsel you by way of caution to forbear from crossing the moor in those dark hours when the powers of evil are exalted. (2.23)
"Well, good-bye," [Holmes] added as the train began to glide down the platform. "Bear in mind, Sir Henry, one of the phrases in that queer old legend which Dr. Mortimer has read to us, and avoid the moor in those hours of darkness when the powers of evil are exalted." (6.18)
"I say, Watson," said the baronet, "what would Holmes say to this? How about that hour of darkness in which the power of evil is exalted?"
As if in answer to his words there rose suddenly out of the vast gloom of the moor that strange cry which I had already heard upon the borders of the great Grimpen Mire. (9.94-5)
These three lines all echo each other: the first quote comes from Hugo Baskerville's manuscript, as he emphasizes that his sons should avoid crossing the moor "in those dark hours when the power of evil are exalted." The second includes a reference by Holmes to the manuscript and "the powers of evil," which he uses to warn Sir Henry. And then the third and final reference to the "powers of evil" that Sir Henry and Watson fear as they cross the moors.
This repetition across the text reminds us that Conan Doyle is a genius, who keeps an eye out for continuity throughout the novel. He keeps the creepiness going.