Goofs

After Holmes and Mortimer sit, Holmes has his pipe in his right hand in his lap, then in his left hand raised.

When Mortimer says "not a soul would have believed it" his left hand is not on his stick, but it is immediately after.

The position of Dr. Watson's left hand as he his writing his first, second and fourth letters back to Sherlock Holmes.

Whenever the action moves to the moor, a chorus of swamp frogs is heard on the soundtrack. This just doesn't happen in England, where amphibians make much less noise, and nothing like the "rivet" of their US cousins.

When the chambermaid is being questioned about Sir Henry's missing boot, Dr Watson's shadow is visible outside the door waiting for his cue to walk into the room.

The Baskerville and Stapleton houses on Dartmoor appear to be lit by gas. At that time, gas was available only in proximity to a gas works and thus only in towns: it was known as "town gas". So people living in remote mansions would have had to rely on candles and oil lamps.

The film is set in 1889, but when Holmes searches the moor with his pocket lantern, it is obvious the prop has been retrofitted with a battery-powered light bulb rather than an alcohol fueled flame. The first battery powered flashlight was invented in 1899.

In opening minutes, Watson is talking about the need for newspaper "clippings" he's doing. But in England they are referred to as "cuttings."

Sir Henry is shown disembarking in London after his voyage from Canada. In fact transatlantic ships sailed to and from Liverpool and Southampton, not London. In the book Holmes met him at London's Waterloo station, where the boat trains from Southampton arrived.

The singer in the "pub" sings "Oi, Oi up she rises in a very bad English accent then, "Early in the morning," in an obvious American accent, and she does it more than once.