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?
and
Alas! to me the idea of an immediate union with my cousin was one of horror and dismay.
and
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?