Your answer about the origins of radio call letters "K," "W," "N," and "A" [How Come, Horizon, Nov. 10] was very good and informative. However, you missed an important fact in the origin of the call sign for WRC, the District's original commercial AM (amplitude modulated) wireless radio station.

WRC stood for Washington Radio Club, a former "amateur" radio club in the Washington area. The original transmitter station and studio were located in the Riggs Bank building at 14th Street and Park Road NW in Columbia Heights. There were two high antenna towers on the building that contained spans of long antenna wires during the 1930 years.

John P. McAdams

Annandale

A report in Horizon [How Come, Oct. 13] incorrectly states the reason that the Tacoma Narrows Bridge collapsed. Nature did not, and could not, generate a wind that varied over many minutes at a constant frequency; furthermore, according to Horizon, this frequency had to match a resonant frequency of the bridge structure. Incorrect and unreasonable.

The truth is that the design of the suspension bridge led to existence of a special, complex, natural-vibration motional pattern of the bridge. This involved jointly sideways twisting and up-and-down doubled motion.

Most suspension bridges do not exhibit this special pattern. The pattern was such that it always gained and absorbed energy from any semi-steady wind, somewhat but not exactly like a kite.

As the bridge always gained energy from the wind, the motion would become larger over time, though some energy was lost into the concrete and steel and ground anchors. This pattern was observed over several months, and solutions were sought. However, in a particularly strong wind, with large amplitude motion, the main cable broke from its anchor, and BOOM!

Suspension bridge designers now carefully design to prevent this particular bridge vibration.

Claude Kacser

Potomac

Your article about Arlington National Cemetery [Nov. 10] states that the cemetery was established by an order of Secretary of War Edwin Stanton of June 15, 1864. That is literally correct, but it ignores the presidential directive that produced Stanton's order.

One day shortly before that date, President Abraham Lincoln was riding horseback with Montgomery Meigs, quartermaster general of the Army, a pleasure they often shared as a brief respite from their duties.

As they rode around the Lee estate, Lincoln asked how the federal goverment could make the best use of that confiscated property. Meigs, who had been greatly concerned with the problem of burials for the vast number of war casualties, suggested that it be made into a national cemetery for the war dead.

The president thought that a wonderful idea and said he would tell Stanton to make it so, with the proviso that the number one plot be reserved for the Meigs family. That was done, with the last spot occupied by Navy Adm. Montgomery Meigs Taylor (ret.) in 1963. This year, the family chipped in for the cost of renovating the various tombs in that plot.

The story about Lincoln and Gen. Meigs was told to me by my great-grandmother, Mary Meigs Taylor. She was living at home with her father while her husband was away in the war and heard the account firsthand. She never forgot it.

Capt. Roy C. Smithill

Annapolis