many thanks for this info - these are potential leads worth exploring.
Unfortunately, Yorkshire/England doesn't quite tie it down, and there were very many George Hirsts around from that part of this country at that time!
I'd still like to be able to get more details about the 1840 Philadelphia Naturalization Application made by George Hirst.
If my relative did emigrate to Philadelphia, this could explain why one of his nephews, Samuel Revell Hirst, subsequently went there for a few years in the 1870's. During the course of his stay, SRH would appear to have met/married [Sarah] Elizabeth Spence[r]. Their first child - Samuel Revell Hirst (my grandfather)- was born in Philadelphia in 1874. They all came back to the UK before 1877.