I don't understand the meaning of this sentence; "The pariah curs were baying the moon - it was only a quarter full and nearly down by midnight, but the dogs slept all day in the heat and they had begun their moon choruses already."
Cur: a pejorative name for a dog (not used much these days, but Orwell wrote this 80 years ago)
A pariah: someone who is socially unacceptable, not liked, or not trusted.
Further in the text, it becomes clear that the dogs baying at the moon are unacceptable to Flory, to the point where he goes out to shoot one of them:
".... Flory had little sleep that night. The pariah curs were baying the moon--it was only a quarter full and nearly down by midnight, but the dogs slept all day in the heat, and they had begun their moon-choruses already. One dog had taken a dislike to Flory's house, and had settled down to bay at it systematically.... It would keep this up for two or three hours,... In the end Flory could stand it no longer. He got up, rummaged in the tin uniform case under his bed for a rifle and a couple of cartridges..."