Under McClellan's strict orders, Washington became less of a national bar-room. The camps were made models of cleanliness, hygiene, and comfort, and schools of strict preparation for the stern work ahead. Carleton often rode through them, and out on the picket-line. Among his other studies, being a musician, he soon learned the various notes and tones of round and conical bullet, of globular and case shot, of shell and rocket, as an Indian learns the various sounds and calls of birds and beasts. Never wearing eye-glasses, until very late in life, and then only for reading, he was able, when standing behind or directly before a cannon, to see the missile moving as a black spot on the invisible air, and from a side view to perceive the short plug of condensed air in front of a ball, which is now clearly revealed by instantaneous photography. He soon noted how the variation in the charge of powder, and the curve of the rifle, changed the pitch of the ball, and how and why certain shells with ragged edges of lead scream like demons, and work upon the nerves by their sound and fury rather than their total of results. He soon discovered that in a battle the artillery, except at short ranges, and in the open, bears no comparison in its killing power to the rifles of the infantry. Like an old soldier, he soon came to look with something like contempt upon the ponderous cannon and mortars, and to admire the low firing of the old veteran musket-men. During those humiliating days, when the stars and bars waved upon Munson's Hill within sight of the Capitol, Carleton saw much of the Confederates through his glass. Picket-firing, though irregular and, probably, from a European point of view, unmilitary, trained the troops to steadiness of nerve. Many things in the first part of the war were done which were probably not afterwards often repeated; for example, the meeting of officers on the picket-lines, who had communications with each other, because they were freemasons. In September, the Confederates fell back from Munson's Hill, and on October 21st the battle at Poolsville, or Ball's Bluff, took place, in which, out of 1,800 Federals engaged, over one-third were killed, wounded or missing. The Fifteenth Massachusetts regiment suffered heavily. Colonel Devens, afterwards major-general and attorney-general, covered himself with glory, but the brave Colonel Baker lost his life.