In recounting local history, one often draws responses that make one revise his understanding of the old days -- not new facts, strictly, but information new to the reporter -- demonstrating that more than just a little knowledge can be a dangerous thing.

By way of background, Metro Scene asserted flatly last week, on the basis of a simplistic reading of history, that a National Park Service sign was wrong in saying that the sturdy old locktender's house at 17th Street and Constitution Avenue NW was part of the Chesapeake & Ohio Canal. The column asserted it was part of the Washington City Canal, built locally to funnel C&O Canal traffic into Washington.

William E. Davies of Falls Church, vice president of the C&O Canal Association, says the locktender's house was indeed part of the C&O Canal, but one that the canal corporation didn't want to build. It's an interesting story.

While the C&O Canal that was built upstream and westward alongside the Potomac River from Georgetown was considered to terminate at Rock Creek, Davies wrote, a $1 million subscription of C&O stock by the city of Washington obligated the canal corporation to dig an easterly connection to the then-existing Washington City Canal along much of what is now Constitution Avenue.

"This part of the C&O Canal east of Rock Creek was referred to as the Washington Branch Canal" of the C&O, Davies declared, its construction in 1832-33 having been demanded by city and federal officials over the protests of the company's other directors.

"At 17th Street, where the Branch Canal joined the Washington City Canal, there was a set of locks to lower the C&O boats to the level of the basin of the City Canal," Davies continued. The locktender's house was part of the C&O project.

Within 30 years after construction, Branch Canal was carrying so little traffic that it was virtually abandoned, Davies wrote, and in 1882 it was sold and later filled in, as was most of the Washington City Canal. A part of the Washington City Canal remained until about 1910. That was along James Creek, in Southwest Washington, now recalled by the name of the James Creek Dwellings public housing project.