...was not only kept up, however, on the flanks, but at two other positions farther to the left, known as Colquitt's and Gracie's salients, countermines were also begun; at Colquitt's on the 10th and at Gracie 's on the 19th. All four of our mines were constantly pushed until the 30th, when the explosion occurred, the total length of our galleries being then about 375 feet. Of the two galleries on each si...