G'day again,I had a look at the Australian National Dictionary for this particular use of "adjectival" ... and it doesn't get a mention. There is an entry (under "Bloody") for "The great Australian adjective" ... ie "Bloody", taking it as a particularly (enthusiastic) Australian usage. This is only cited from 1894 ... not then 1870s, which is Kelly's period.
I think Carey is trying to use later "equivalents" o convey a sense of style ... in a much later idiom ... maybe ... ?!?
Regards,
Bob Bolton