On the lower Copper River is Childs Glacier, which is seriously threatening to destroy a steel railway bridge just completed. The rate of forward motion in Childs Glacier increased during the winter of 1909-10 so that part of the margin of the glacier changed its forward movement from nothing to two and as much as eight feet a day.... Childs Glacier is ten to twelve miles long, not much over a mile wide in the mountain valley, but it widens to over three miles in Copper River Valley. Its front is a precipitous white wall 250 to 300 feet high, and is swept at the base by Copper River.... In August, 1909, Childs Glacier was advancing at about its normal rate--four feet a day at a point near the north side and perhaps six or seven feet a day in midglacier. The melting and the many icebergs discharged from the terminal cliff at that time just about balanced this advance, so that the front of the glacier remained in about the same place.... During the winter and early spring of 1909-10, however, the glacier began to advance more rapidly, buckling up the ice of the frozen river. In June 1910 the ice-front had moved forward from 920 to 1225 feet, narrowing the river to 400 or 500 feet. Every time the ice cliff was sufficiently undercut by the river, great masses of ice would cascade down the front, raising a gigantic wave in the river.... During the advance the waves washed up over a bank five to twenty-five feet in height and rushed back 100 or 200 feet into the alder thicket. Ice blocks, up to ten tons in weight were thrown in among the trees. Stones a foot or two in diameter were hurled into the thicket. Alders nine to eleven inches in diameter were stripped of leaves and bark and bent backward or broken off short, or uprooted or buried beneath the gravel and boulders and macerated trunks of other trees. The river bank, which was cut back some in the preceding year was in 1910 being fairly eaten up by the iceberg waves which crossed the river, fifty to sixty feet by actual measurement having been removed along the bank of the stream facing the glacier.