Fort Sumner, on the Potomac above Georgetown, and Fort Lincoln, near Bladensburg, commanding the Baltimore and Ohio Railroad and the upper Anacostia. Fort Lincoln was profusely but not heavily armed. It had two 8-inch siege-howitzers, six 32-pounder sea-coast guns, one 24-pounder siege-gun, three 24-pounder seacoast guns, four 12-pounder field-guns, and eight 6-pounder field-guns en barbette, with two 24-pounder field-howitzers en embrasure. This concludes the list of the smooth-bores, but there were also a 100-pounder Parrott and four 20-pounder Parrotts. Fort Lincoln was a bastioned Fort of four faces. One of the 20-pounder Parrotts is just visible over the top of the storehouse, and the 100-pounder is in full view in the far corner of the fort. This was one of the first points fortified on the Northern lines about Washington. The spade, seen leaning against the house to the left of the pile of boxes, was the great weapon of warfare. The lower photograph shows Company H of the Third Massachusetts Heavy Artillery manning the guns. Their muskets have been leaned against the parapet, and the pile of shells to the right makes the great guns glaring down the valley seem formidable indeed. The Third Massachusetts was organized from unattached companies of heavy artillery in August, 1864, for the defense of Washington.