This is pretty neat. It feeds into a project I'm in the middle of beginning to structure and hopefully will begin undertaking in earnest soon. When I do, I will post results and conclusions.
It also highlights something of a myth around Quakers and race, particularly the underground railroad. Historically if Quakers are remembered as a group at all it is in regards to the abolition movement, owing in no small part to the role of the Quaker couple in "Uncle Tom's Cabin" and the widely known stories of Levi Coffin and John Woolman. The historian in the article does mention that not all Quakers would offer help but that they were the most consistently anti-slavery. I'm not sure of the accuracy of that statement, one could check it in Vanessa July's and Donna McDaniel's exhaustive volume Fit for Freedom: Not for Friendship. However the historian does right by first and foremost mentioning the type of slaves that would head north and highlighting the extraordinary hardships that they went through. Anything abolitionists did to help should be considered auxillary to what slaves did for themselves.
The closing lines though, are all too often what summaries about Quakers and the underground railroad end up as unfortunately.