It took me about a half a day to find this. After about an hour of calculating, I determined that Camp Holmes was located about where Wake Forest Road hits Capital Blvd north of downtown Raleigh. Attached is a map I photocopied from the state archives superimposed over a Google map of the area. Because much of the modern Pigeon house creek more of a canal now, I relied mostly on the railroad, indicated by the dashed line running south of the camp. The official map is one of the defenses of Raleigh, created in 1863 for Governor Zebulon Vance, and several close-up negatives are available for viewing at the state archives free of charge. You're welcome.