I was reading Frankenstein and I've noticed that the word after the exclamation mark usually isn't capitalised (unless it's a noun). Some of the quotes I've found:
Alas! who is safe, if she be convicted of crime?
Alas! to me the idea of an immediate union with my cousin was one of horror and dismay.
Great God! what a scene has just taken place!
Why the word after the exclamation mark does not begin with a capital letter?
Has the rule for using exclamation marks changed and when did it change?