What was the appearence of the hound that people saw before Sir Charles's death?
i mean that the appearence of a hound that was seen by people of around the hall saw .and who was plucking Hugo's throat.
The answer to this question can be found in Chapter 2. There, Dr. Mortimer is reading to Holmes and Watson from an account that was given to him by Sir Charles Baskerville. This account is dated 1742.
According to this account, the hound that was seen plucking at Sir Hugo Baskerville's throat was absolutely hellish. Its appearance was so terrible that one of the men who saw it died that night and the other two were broken men for life. There is little given in the way of specifics about its appearance other than to say that it was very big and had blazing eyes and dripping jaws. Here is the relevant passage:
... there stood a foul thing, a great, black beast, shaped like a hound, yet larger than any hound that ever mortal eye has rested upon. And even as they looked the thing tore the throat out of Hugo Baskerville, on which, as it turned its blazing eyes and dripping jaws upon them...