... at Mechanicsville and Beaver Dam. In spite of a constantly erroneous statement of numbers, this engagement was between four brigades (not counting brigades present, but not materially engaged) of Fitz John Porter , and five brigades of A. P. Hill, assisted just before dusk by Ripley's brigade of D. H. Hill's division. Gregg's and Branch's brigades, of A. P. Hill's, took no part in the assault on the fortifie...