This is all about what words belong together. There are some grammatical mistake in the above sentence though: 1. apallingLY good humour = refers to his sense of humour 2. sore + perplexed: these two words belong together. When you are extremely perplexed we say: "sore perplexed".

'appaling good-humour' is a sarcastic expression ,in fact his manner was more repulsive and appaling means 'alarming but in a terrible way. Quoting from the same passage: " He was loud and boisterous, always laughing and singing, and never able to work consecutively at anything." When he acted this way ,that was supposed to be his own agreeable cheerful mood ( laughing and singing),but they perceived it as an alarming awful behavior. The word 'sore' in this context is very 'archaic' and means greatly or very perplexed. The quotation is of an essay written in 1903 after all.