the ice into central Pennsylvania (Clark and Ciolkosz 1988; Martin 1958; Watts 1983). Vegetation zones shifted northwards rapidly as the ice melted and retreated (Delcourt and Delcourt 1987; Gaudreau 1988; Webb et al. 1987), but spruce trees were common in the Middle Atlantic region until about 1

County, Pennsylvania. 34Worner, William F., "The Race Riots", 182-187; and Ellis and Evans, A History of Lancaster County, 574. For an example of writings about splits in other black communities see Litwack, North of Slavery, 151-186, 247-279; August Meier, "Negro Class Struc- ture and Idealogy in the

Pennsylvania Anti-Slavery Society, compiled a history of his involvement in the Underground Railroad. An interesting letter from Whipper was reprinted that recounted the latter's efforts in Columbia between 1847-61. Looking back on the decades preceding the war Whipper summarized:3 [...] it would have been